Microbiology KP notes Flashcards

Question 1

Q

what is the procedure for the Gram stain?

Answer

A

apply a primary stain such as crystal violet (purple) to heat fixed bacteria
add iodine which binds to crystal violet and helps fix it to the cell wall
decolorise with ethanol or acetone
counterstain with safranin (pink)

Question 2

Q

what are the results of the Gram stain?

Answer

A

in gram-negative bacteria, the decoloriser interacts with the lipids and cells lose their outer lipopolysaccharide membrane
and the crystal violet-iodide (CV-I) complexes, thus they appear pink with counterstain
in gram-positive bacteria, the decoloriser dehydrates the cell
wall and the CV-I gets trapped in the multi-layered peptidoglycan resulting in a purple appearance with counterstain

Gram positive = purple
Gram negative = pink

Question 3

Q

what is the Ziehl-Neelsen stain? what are the results?

Answer

A

Gram stain can differentiate most bacteria
but mycobacteria e.g. TB are acid-fast bacilli that do not take up the gram stain
instead they take up a stain called Ziehl-Neelsen

acid-fast bacilli = red e.g. Mycobacterium
non acid-fast bacilli = blue e.g. E.coli

Question 4

Q

what is the catalase test? what are the results?

Answer

A

• essentially add H2O2 to bacteria and see for bubbling reaction (positive reaction)
• used to differentiate between staphylococci
and streptococci
• Staphylococci are catalase positive
• Streptococci are catalase negative
• many Gram negative bacteria e.g. E.coli and fungi (aspergillus spp.) are catalase positive

Question 5

Q

what is the coagulase test? what are the results?

Answer

A

coagulase is an enzyme produced by Staphylococcus. aureus that converts (soluble) fibrinogen in plasma to (insoluble) fibrin
other staphylococci do not produce coagulase, e.g. S. epidermis
thus this test distinguishes S. aureus (coagulase positive) from other staphylococci (coagulase negative)
S. aureus is coagulase positive = clumping
other staphylococci are coagulase negative = no clumping

Question 6

Q

what is the haemolysis test?

Answer

A

haemolysis is the ability of bacteria to break down red blood cells in blood agar
it requires the expression of haemolysin
very useful for classifying streptococci

Question 7

Q

what is alpha haemolysis?

Answer

A

an indistinct zone of partial destruction of red blood cells (RBCs) appears around the colony, often accompanied by a greenish to brownish discolouration of the medium (opaque)

Question 8

Q

what are examples of alpha haemolytic organisms?

Answer

A

Streptococcus pneumoniae (can cause lobar pneumonia & meningitis) is alpha haemolytic
S. oralis
S. milleri
S. sanguis
many oral streptococci are alpha haemolytic
some alpha haemolytic species can cause serious pathology such as infective endocarditis - caused by viridans streptococci
S. intermedius is also alpha haemolytic

Question 9

Q

what is beta haemolysis?

Answer

A

a clear, colourless zone appears around the colonies, in which the red blood cells have undergone complete lysis

Question 10

Q

what are examples of beta haemolytic organisms?

Answer

A

Streptococci pyogenes, Streptococci agalactiae and many other streptococci are beta haemolytic
many other bacteria besides streptococci can be beta
haemolytic including S. aureus and listeria monocytogenes

Question 11

Q

how can S. aureus be differentiated from other beta haemolytic organisms?

Answer

A

it’s important to differentiate staphylococcus aureus and this can be done by:
• looking at appearance on blood agar - will be creamy
yellow
• also will have a positive coagulase test

Question 12

Q

how can you differentiate between different beta haemolytic bacteria?

Answer

A

by using Lancefield grouping (detecting surface antigens)

Question 13

Q

what is Lancefield grouping?

Answer

A

used to differentiate between beta haemolytic bacteria
detects surface antigens
A, C, G = tonsillitis and skin infection
B = neonatal sepsis and meningitis
D = UTI/enterococci

Question 14

Q

what is gamma haemolyis?

Answer

A

no haemolysis of RBCs

Question 15

Q

what are examples of organisms showing gamma haemolysis?

Answer

A

enterococcus faecalis
Staphylococcus saprophyticus
Staphylococcus epidermidis
S. bovis
S. mutans
S. milleri

Question 16

Q

what is the optochin test?

Answer

A

place optochin soaked disc on agar and watch bacterial growth
test to differentiate between streptococcus pneumoniae (causes lobar pneumonia and meningitis - sensitive to optochin so will be a clear zone around the disc
Viridans streptococci (infective endocarditis) and other alpha haemolytic streptococci are resistant to it so there will be growth around the disc

Question 17

Q

what are results of the optochin test?

Answer

A

sensitive = Streptococci pneumoniae; clear zone of no growth around disc

resistant = Viridans streptococci; growth around disc

Question 18

Q

what is the oxidase test?

Answer

A

tests if micro-organism contains a cytochrome oxidase - an enzyme of the bacterial electron transport chain
all bacteria that are oxidase positive are aerobic
bacteria that are oxidase negative may be either aerobic or anaerobic

Question 19

Q

what are some oxidase positive bacteria?

Answer

A

P. aeruginosa
V. cholerae
Campylobacter e.g. C. jejuni
Helicobacter

Question 20

Q

what are the results of the oxidase test?

Answer

A

oxidase positive = blue - bacteria is aerobic e.g. V. cholerae
oxidase negative = no colour change - bacteria may be aerobic or anaerobic

Question 21

Q

what does MacConkey agar grow? what are its uses?

Answer

A

only grows Gram negative bacilli
good at differentiating between lactose-fermenting and non-lactose fermenting Gram negative bacilli such as enterobacteria (gut coliforms)
bile salts present on this agar inhibit Gram positive bacteria and inhibit the swarming of a Gram negative bacterium Proteus spp.

Question 22

Q

how does MacConkey agar show lactose/non-lactose fermenting bacteria?

Answer

A

has a pH indicator on it so bacteria that ferment lactose and thus produce acid will make the agar appear pink/red

Question 23

Q

what are some lactose fermenting bacteria that can be identified on MacConkey agar?

Answer

A

E. coli
Klebsiella pneumonia
Enterobacter spp.

Question 24

Q

what are some non-lactose fermenting bacteria that can be identified on MacConkey agar?

Answer

A

Salmonella spp.

- Shigella spp.

Question 25

Q

what is the use of XLD agar?

Answer

A

used to differentiate Salmonella and Shigella mainly

Question 26

Q

what are the results of MacConkey agar?

Answer

A

Gram negative bacilli only
will turn pink/red if lactose fermenting bacteria e.g. E. coli
will turn white/transparent if non-lactose fermenting e.g. Salmonella

Question 27

Q

what are the results of XLD agar?

Answer

A

Salmonella = red/pink colonies some with black spots

Shigella = red/pink colonies

Question 28

Q

what are some Gram positive cocci?

Answer

A

Staphylococci
Streptococci
Enterococci
anaerobic Streptococci e.g. peptostreptococci

Question 29

Q

what are some Gram negative cocci?

Answer

A

Neisseria
Moraxella
anaerobic cocci e.g. Veillonella spp.

Question 30

Q

what are some Gram positive bacilli?

Answer

A

Bacillus e.g. B. anthracis
Clostridia
Corynebacteria e.g. C. diptheriae
Listeria monocytogenes
anaerobic bacilli e.g. Clostridia
Propionibacteria

Question 31

Q

what are some Gram negative bacilli?

Answer

A

E. coli
Campylobacter
Pseudomonas
Salmonella
Shigella
Proteus

Question 32

Q

give some examples of aerobic Gram positive cocci?

Answer

A

staphylococcus and streptococcus

Question 33

Q

give some examples of Staphylococcus?

Answer

A

S. aureus and S. epidermidis

Question 34

Q

give some examples of anaerobic Gram positive cocci?

Answer

A

peptostreptococcus

Question 35

Q

give some examples of anaerobic Gram negative bacilli?

Answer

A

Bacteroides (e.g. B. fragilis)

Question 36

Q

what are some examples of aerobic Gram negative bacilli?

Answer

A

coliforms
pseudomonads
vibrio
parvobacteria

Question 37

Q

what areas of the body are sterile and non-sterile?

Answer

A

non-sterile: nasal cavity, larynx, stomach, colon

sterile: lungs, gall bladder, kidneys, eye, CSF

Question 38

Q

what is the growth rate of bacteria?

Answer

A

you measure bacterial growth by shining light on bacteria and measuring absorption
bacteria divide by binary fission
the growth lag is due to the fact the bacteria are taking in the nutrients needed to divide and grow
then there is exponential growth until the nutrient runs out
viable = death phase

Question 39

Q

what is transformation in bacteria?

Answer

A

the genetic alteration of a bacterial cell via the uptake of an exogenous substance e.g. via plasmid

Question 40

Q

what is transduction in bacteria?

Answer

A

process by which foreign DNA is introduced into a bacteria via vector or virus e.g. via a bacteriophage (virus)

Question 41

Q

what is conjugation in bacteria?

Answer

A

the transfer of genetic material between bacterial cells by direct cell-cell contact e.g. via sex pilus

Question 42

Q

what is the normal habitat of Staphylococcus? how many species are there?

Answer

A

normal habitat is on the nose and skin
at least 40 species
can be coagulase positive (clumping) or negative (no clumping)
coagulase converts fibrinogen to fibrin i.e. clot - some bacteria produce it
to protect against white blood cells e.g. S. aureus

Question 43

Q

what is the common clinical presentation of S. aureus?

Answer

A

pain in shoulder
elevated temperature
MRI scan - disc injection and osteomyelitis (bone infection) C6 and C7
blood cultures show staphylococcus aureus
treat with flucloxacillin (antibiotic) for 3 months
Staph. aureus is responsible for around 90% of osteomyelitis

Question 44

Q

how is S. aureus spread?

Answer

A

aerosol and touch e.g. coughing and breathing

Question 45

Q

what is MRSA resistant to?

Answer

A

Beta-lactams antibiotics
gentamicin
erythromycin
tetracycline

Question 46

Q

what is the virulence/pathogenic factors of S. aureus?

Answer

A

pore-forming toxins (some produce these) e.g:
• PVL toxin which is prodcued by many MRSA strains and causes haemorrhagic pneumonia
• alpha-haemolysin which can induce apoptosis (at low
levels) or cause widespread necrosis (at high levels)
proteases e.g:
• exfoliatin which causes scalded skin syndrome
toxic shock syndrome toxin (TSST) which stimulates cytokine release
protein A which is a surface protein which binds
immunoglobulins in wrong orientation

Question 47

Q

what are the pore-forming toxins of S. aureus? what are their actions?

Answer

A

• PVL toxin which is prodcued by many MRSA strains and causes haemorrhagic pneumonia
• alpha-haemolysin which can induce apoptosis (at low
levels) or cause widespread necrosis (at high levels)

Question 48

Q

what are associated conditions of S. aureus?

Answer

A

wound infections (staph. aureus is very good at colonising these)
abscesses
osteomyelitis
scalded skin syndrome
toxic shock syndrome
food poisoning

Question 49

Q

what are some coagulase negative bacteria?

Answer

A

S. epidermis and S. saprophyticus

Question 50

Q

what are features of S. epidermis?

Answer

A

opportunistic infections in prosthetic limbs and catheters

- its main virulence factor is its ability to form persistent biofilms

Question 51

Q

what can S. saprophyticus cause?

Answer

A

acute cystitis

Question 52

Q

in what ways can streptococci be classified?

Answer

A

haemolysis
Lancefield typing
biochemical properties

Question 53

Q

what is Lancefield typing?

Answer

A

a method of grouping catalase negative and coagulase negative bacteria based on the bacterial carbohydrate cell surface antigens

Question 54

Q

what are important groupings in Lancefield typing?

Answer

A

Group A - Strep. pyogenes

Group B - Strep. agalactiae; neonatal infections

Question 55

Q

what are some infections that are caused by Strep. pyogenes?

Answer

A

wound infections such as cellulitis
tonsillitis and pharyngitis
otitis media
scarlet fever (caused by erythrogenic toxin)

Question 56

Q

what are complications of Strep. pyogenes?

Answer

A

rheumatic fever
glomerulonephritis
some strains produce erythrogenic toxin which is responsible for scarlet fever, this toxin is a super-antigen meaning it gives rise to an exaggerated immunological response and increased
circulating cytokine levels
infection with any strain of Strep pyogenes can give rise to complications that are immunologically mediated, so prompt treatment is required to reduce risks
assessment of risk can be estimated from the anti-streptolysin O titre

Question 57

Q

what can be used to assess risk for complications of Strep. pyogenes?

Answer

A

anti-streptolysin O titre

Question 58

Q

what are the secreted virulence/pathogenic factors of Strep. pyogenes?

Answer

A

hyaluronidase - spreading
streptokinase - breaks down clots
C5a peptidase - reduces chemotaxis
streptolysins O & S toxin - binds cholesterol
erythrogenic toxin - exaggerated response

Question 59

Q

what is the action of hyaluronidase in Strep. pyogenes?

Question 60

Q

what is the action of streptokinase in Strep. pyogenes?

Answer

A

breaks down clots

Question 61

Q

what is the action of C5a peptidase in Strep. pyogenes?

Answer

A

reduces chemotaxis

Question 62

Q

what is the action of streptolysins O and S toxin in Strep. pyogenes?

Answer

A

binds cholesterol

Question 63

Q

what is the action of erythrogenic toxin in Strep. pyogenes?

Answer

A

exaggerated response

Question 64

Q

what are surface virulence/pathogenic factors of Strep pyogenes?

Answer

A

hyaluronic acid capsule - protection

* M protein - surface protein that encourages complement degradation

Answer 64

A

protection

Answer 65

A

surface protein that encourages complement degradation

Answer 66

A

heavy smoker with nasal congestion and fever
2 days later gets cough and severe chest pain
rust-coloured sputum
chest X-ray shows consolidation (lung filled with liquid)
blood and sputum culture show Strep. pneumoniae (draughtsman colonies)

Answer 67

A

pneumonia
otitis media (middle ear infection)
sinusitis
meningitis

Answer 68

A

impaired mucus trapping e.g. viral infection
hypogammaglobulinemia - low levels of serum immunoglobulins which are required for efficient phagocytosis
asplenia - since spleen produces protein called tuftsin which acts to enhance phagocytosis so with no spleen then no tuftsin and this impairs phagocytosis and thus risk of infection
diabetes
renal disease
sickle cell disease
very young (younger than 2) since immune response to
polysaccharide antigens is very poor

Answer 69

A

polysaccharide capsule (84 types) - is antiphagocytic - there is a polyvalent vaccine available for those under 2 but this only protects against 23/84 types
teichoic acid binds to choline receptors
peptidoglycan helps protect bacteria
pneumolysin cytotoxin is a pore-forming toxin

Answer 70

A

(84 types) - is antiphagocytic - there is a polyvalent vaccine available for those under 2 but this only protects against 23/84 types

Answer 71

A

binds to choline receptors

Answer 72

A

helps protect bacteria

Answer 73

A

pore-forming toxin

Answer 74

A

collective name for oral streptococci
alpha or non-haemolytic
some cause dental caries and abscesses

Answer 75

A

S. sanguis and S. oralis

Answer 76

A

most pathogenic are the milleri group:

S. intermedius
S. anginosis
S. constellatus
causing deep organ abscesses e.g. in brain & liver

Answer 77

A

child with severe sore throat
fever and malaise for 2 days
lymphadenopathy (swollen) in neck
rapid breathing
thick greyish membrane on tonsils

Answer 78

A

gram positive rods/bacilli

Answer 79

A

treated with anti-toxin (pre-formed antibody to toxin) and erythromycin (antibiotic helps remove symptoms and stop carriage and spread but
does not destroy pathogen)

Answer 80

A

droplet spread

Answer 81

A

caused by the production of a toxin which inhibits protein synthesis (inactivates elongation factor-2 in host cells by adding ADP-ribosyl group to aa dipthamide)

Answer 82

A

prevention by vaccination with toxoid (inactivated toxin)
can grow in the presence of potassium tellurite - selective method for isolating this bacteria from throats of patients

Answer 83

A

lipopolysaccharide is an endotoxin and forms the outer leaflet of the outer membrane of gram-negative bacteria and comprises:
- Lipid A - the toxic portion of LPS that is anchored in the outer leaflet of the outer membrane
- core (R) antigen - short chain of sugars, some are unique to LPS
- somatic (O) antigen - a highly antigenic repeating chain of
oligosaccharides

Answer 84

A

the toxic portion of LPS that is anchored in the outer leaflet of the outer membrane

Answer 85

A

short chain of sugars, some are unique to LPS

Answer 86

A

a highly antigenic repeating chain of oligosaccharides

Answer 87

A

the toxin/effector (protein) needs to travel past two membranes rather than just one

Answer 88

A

K antigen (EPS capsule)
H antigen (flagellum)
O (somatic) antigen (LPS)

Answer 89

A

Shigella has no H antigen since it does not have flagellum

- Salmonella does have a H antigen since it does have a flagellum

Answer 90

A

rods/bacilli
most are motile i.e. have flagella
some are intestinal parasites
are able to grow in anaerobic conditions
MacConkey agar is used to differentiate between lactose and non-lactose fermenting

Answer 91

A

• commensals - most abundant facultative anaerobe (facultative means
is able to i.e. is able to respire anaerobic, but not only anaerobically, can respire aerobically too)
• they have flagella
• there are many serotypes/strains
• they all share a common ‘core’ genome

Answer 92

A

wound infections (surgical)
Urinary Tract Infections (UTIs) - also known as cystitis,
75%-80% female UTIs are from catheterisation
gastroenteritis in children and adults
travellers’ diarrhoea
bacteraemia - the presence of bacteria in the blood
meningitis in infants - rare in the UK

Answer 93

A

pathogenic E.coli contains blocks of genes that are not present in commensal E.coli (that live in the gut)
many pathogenic E.coli have ‘acquired’ pathogenicity from other bacteria by ‘mating’ and acquiring pathogenic blocks of genes

Answer 94

A

strain is called enterotoxigenic (ET) E.coli (ETEC)
has pilli which enable it to adhere to the tissue of the small intestine
when it binds to the tissue it releases a labile toxin that alters the role of the Gs protein on the GI cell surface meaning it can no longer stimulate adenyl cyclase resulting in more Cl- being released into the GI lumen
this results in water following, resulting in diarrhoea

Answer 95

A

S. dysenteriae
S. flexneri
S. boydii
S. sonnei (commonest cause)

Answer 96

A

all four species cause damage to the intestinal mucosa that result in:

acute infection of the large intestine
painful diarrhoea often with blood and mucus in the stools

Answer 97

A

the infective dose is just 100 bacteria thus extremely easy to be infected

Answer 98

A

spread from person-to-person or via contaminated water or food

Answer 99

A

• these are found in the gut-associated lymphoid tissue
(GALT) of the Peyer’s patches and in the mucosa-
associated lymphoid tissue (MALT)
• these cells initiate mucosal immunity responses and allow for the transport of microbes across the epithelial cell layer from the gut lumen where interactions with immune cells can take place

Answer 100

A

bacteria are acid-tolerant so can survive and pass through the stomach
bacteria target microfold (M) cells
shigella induce their own uptake by M-cells, they then cross the epithelial cell layer where they are engulfed by macrophages
however, once engulfed they induce the apoptosis of the macrophages resulting in the release of damaging free radicals resulting in an inflammatory response and cell damage
eventually the bacteria will be destroyed by neutrophils

Answer 101

A

shiga toxin

Answer 102

A

some shigella bacteria also release a shiga toxin which disrupts protein synthesis resulting in necrosis:
• this toxin targets the kidney resulting in haemolytic uraemic syndrome which can lead to death
• shiga toxin is also produced by some E.coli e.g. EHEC

Answer 103

A

S.enterica - responsible for salmonellosis (any infection caused with salmonella)
S.bongori - rare, results from reptile contact

Answer 104

A

gastroenteritis
enteric fever; typhoid
bacteraemia

Answer 105

A

frequent cause of food poisoning from milk and poultry
6-36 hour incubation
resolves in a week
localised infection

Answer 106

A

systemic disease
caused by Salmonella typhi and Salmonella paratyphi
spread is faecal-oral
results in fever, headache, dry cough
splenomegaly and hepatomegaly
diarrhoea may develop

Answer 107

A

Salmonella typhi and Salmonella paratyphi

Answer 108

A

faecal-oral

Answer 109

A

presence of bacteria in the blood - uncommon

Answer 110

A

ingestion of contaminated food/water
has a high infective dose - need to ingest a significant amount for infection
Salmonella mediates its endocytosis across the gut lumen

Answer 111

A

• bacteria presence results in chemokine release and
neutrophil recruitment
• this results in neutrophil-induced tissue injury due to the inflammatory response
• there is fluid and electrolyte loss due to cell damage
resulting in diarrhoea
• eventual inflammation/necrosis of gut mucose

Answer 112

A

• migrates to the basolateral membrane of cells in the
intestinal lumen - Peyers patch where it results in
inflammation and ulceration - diarrhoea
• however, initially there is little damage to the gut mucosa
• bacteria is then engulfed and survives then spreads
systemically via the lymph nodes
• then enters bloodstream via the thoracic duct and then
multiplies in the macrophages of the liver, spleen and bone marrow resulting in septicaemia which results in massive
fever
• then spreads to the gall bladder from the liver where person can be in a carrier state from 1 year to the rest of their life

Answer 113

A

opportunistic
causes different nosocomial (hospital acquired) infections:
• pneumonia
• bloodstream infections
• wound or surgical site infections
• meningitis

Answer 114

A

facultative anaerobe
curved rods/bacilli with single polar flagellum
results in cholera - the most severe diarrhoeal disease

Answer 115

A

faecal-oral route - faecal contaminated water and uncooked shellfish

Answer 116

A

high infective dose is required since its sensitive to acid i.e. acid in stomach - requires many to get past the stomach

Answer 117

A

5 hours (multiplies in small intestine)

Answer 118

A

results in voluminous watery (rice-water) stools i.e. secretory diarrhoea
can lose 20 litre/day plus electrolytes, this results in:
• dehydration and subsequent death
• 60% mortality
there is no blood or fever since there is no invasion or damage to mucosa

Answer 119

A

80% treated with oral rehydration

Answer 120

A

pilli - required for colonisation

* Cholera toxin - acts in same way as E.coli labile toxin

Answer 121

A

results in uncontrolled cyclic AMP production
which results in the activation of protein kinases
which causes the modification of ion transporter activity causing the loss of Cl- & Na+ resulting in massive H2O loss

Answer 122

A

motile - single polar flagellum
opportunistic (serious cause of nosocomial infections)
multiple antibiotic resistance

Answer 123

A

burn/surgical wounds
UTIs (catheters)
keratitis (inflammation of cornea)

Answer 124

A

neutropenic (low on neutrophils) patients (leukaemia, chemotherapy, AIDS)

Answer 125

A

nosocomial pneumonia

Answer 126

A

cystic fibrosis

Answer 127

A

have poor functioning Cl- transporters meaning they have dehydrated lung mucus which is the perfect environment for bacteria to grow
virtually impossible to remove pseudomonas in cystic fibrosis patient since antibiotic resistant

Answer 128

A

exclusively human parasite
nasopharyngeal carriage in 25-80% population
fastidious (specific requirement for survival)
non-motile

Answer 129

A

young children and adult smokers

Answer 130

A

important cause of meningitis, when it crosses the blood-brain barrier (less than 5yrs) and bronchopneumonia
epiglottitis, sinusitis, otitis media (ear infection)
bacteraemia
cystic fibrosis and COPD lung infections

Answer 131

A

specific requirement for survival
• will not grow on blood agar which supports growth of many other fastidious bacteria - since it cannot access haem in this form
• will only grow on chocolate agar:
blood agar which has been heated to 80 degrees to allow the release of haem by red blood cells

Answer 132

A

blood agar which has been heated to 80 degrees to allow the release of haem by red blood cells

Answer 133

A

• pilli: adherence to epithelial cells and mucin
• capsule:
- commensals and respiratory tract pathogens are non-capsulate
- invasive strains are capsulate (can penetrate the
nasopharyngeal epithelium)
• lipopolysaccharide (LPS) endotoxin - results in inflammation

Answer 134

A

pertussis is whooping cough
short (sometimes oval) rods/bacilli
highly contagious with a low infect dose

Answer 135

A

aerosol transmission

Answer 136

A

• adhere to the ciliated epithelia of the upper respiratory tract/trachea
• non-specific flu-like symptoms followed by paroxysmal coughing
(cough followed by inhalation resulting in whooping sound)
• can lead to sub-conjunctival haemorrhage

Answer 137

A

• non-flagellated diplococci (go around in pairs)
• present in polymorphonuclear lymphocytes of CSF or urethral
discharge during infection

Answer 138

A

N. meningitidis

N. gonorrhoeae

Answer 139

A

present in the nasopharynx of 5-10% of the population
(asymptomatic)
person-person aerosol transmission (university or barracks)

Answer 140

A

crosses the nasopharyngeal epithelium and enters the
bloodstream in a small proportion of colonised individuals:
- asymptomatic bacteraemia (if low numbers of bacteria) or septicaemia if high
- meningitis - the colonisation of the subarachnoid space after crossing the blood-brain barrier
- there is a very high risk of mortality in the septicaemic form if not treated

Answer 141

A

• capsule is major virulence determinant:
- non-capsulated is only found in the nasopharynx
- capsule is anti-phagocytic
• pilli on bacteria promote colonisation and cell invasion
• lipopolysaccharide results in cytokine cascade and
inflammatory response which can lead to sepsis

Answer 142

A

capsule is major virulence determinant:

non-capsulated is only found in the nasopharynx
capsule is anti-phagocytic

Answer 143

A

pilli on bacteria promote colonisation and cell invasion

Answer 144

A

LPS results in cytokine cascade and inflammatory response which can lead to sepsis

Answer 145

A

not a commensal but can be asymptomatic (30% of infected females)
person to person only
non-capsulated unlike N.meningitis

Answer 146

A

it’s an STD resulting in:
• urethritis with additional infection of female genitalia
• can lead to infection of the fallopian tubes if infection
ascends

Answer 147

A

C. jejuni and C. coli

Answer 148

A

• spiral rods/bacilli
• most common cause of food poisoning in UK and US:
- undercooked poultry e.g. BBQ
- unpasteurised milk
• has a low infective dose

Answer 149

A

Campylobacter

undercooked poultry e.g. BBQ
unpasteurised milk

Answer 150

A

results in mild-sever diarrhoea often with blood - usually self-limiting within a week
Campylobacter shed in faeces for around 3 weeks

Answer 151

A

invasins and cytolethal distending toxin (CDT)

Answer 152

A

invades ileal and colonic epithelial cells

* resulting in local acute inflammatory response i.e. tissue damage

Answer 153

A

arrests the cell cycle meaning target cells swell and lyse

Answer 154

A

require CO2 (microaerophilic)

* spiral shaped

Answer 155

A

present in 50% of global population but only a fraction will develop the disease

Answer 156

A

major role in gastritis and peptic ulcer disease

* implicated in gastric adenocarcinoma

Answer 157

A

urease - hydrolyses urea to generate ammonia to act as a buffer to gastric acid

Answer 158

A

very small and non-motile

Answer 159

A

elementary bodies; dormant

- reticulate bodies; metabolically active and fragile

Answer 160

A

infectious
enter cell through endocytosis
prevent phagosome fusion
dormant

Answer 161

A

replicative
non-infectious
metabolically active
fragile

Answer 162

A

Chlamydia trachomatis

Answer 163

A

can spread to the uterus and ovaries resulting in pelvic inflammatory disease
usually asymptomatic

Answer 164

A

can cause conjunctivitis (STD)

* can cause trachoma - blindness that is spread via flies

Answer 165

A

respiratory tract
urinary tract
GI tract
meningitis
STIs
wound infections

Answer 166

A

Bordetella pertussis

* Haemophilus influenzae

Answer 167

A

some E.coli strains

* Klebsiella pneumoniae

Answer 168

A

Vibrio cholera
Shigella dysenteriae
some E.coli strains
Campylobacter jejuni
Helicobacter pylori

Answer 169

A

Neisseria meningitidis

* Haemophilus influenzae

Answer 170

A

Klebsiella pneumoniae

* Chlamydia trachomatis

Answer 171

A

Pseudomonas aeruginosa

* some E.coli strains

Answer 172

A

eukaryotic - have a nuclear membrane
chitinous cell wall
heterotrophic: get nutrients from what they are living on
move by means of growth or spore release

Answer 173

A

type of fungi that is a small single celled organisms that divide by budding

Answer 174

A

type of fungi that form multicellular hyphae and spores

Answer 175

A

some fungi exist as both yeasts and moulds switching between the two when
conditions suit - these are dimorphic fungi

Answer 176

A

Coccidioides immitis

Answer 177

A

grow as mould at ambient temperature

* convert to yeast form at body temperature after inhalation

Answer 178

A

only a few fungal forms can actually infect humans
fungi have an inability to grow at 37 degrees (body temperature)
fungi also cannot evade the adaptive/innate immune response

Answer 179

A

enormous since most will have had at least one in lifetime e.g nappy rash,
tinea pedis (athletes foot) and fungal asthma
however life-threatening fungal infection is rare in healthy hosts

Answer 180

A

Candida line infections
Pneumocystis
invasive aspergillosis

Answer 181

A

intra-abdominal infections

Answer 182

A

fungal asthma

- travel associated fungal infections e.g. dimorphic fungi

Answer 183

A

to achieve inhibitory levels of the agent at the site of the infection without host cell toxicity

Answer 184

A

relies on identifying molecules with selective toxicity for organism targets

Answer 185

A

target does not exist in humans
target is significantly different to human analogue
drug is concentrated in organism cell with respect to humans
organism has an increased permeability to the compound
human cells are ‘rescued’ from toxicity by alternative metabolic pathways

Answer 186

A

in general the concept of selective toxicity is much harder to achieved for fungi as opposed to bacteria due to the fact that fungi are eukaryotic, and so are human cells thus they are more similar and thus harder to differentiate

Answer 187

A

DNA/RNA synthesis and protein synthesis
similar to mammalian
drugs targeting these: Flucytosine

Answer 188

A

mannoproteins
B1,3 glucan
B1,6 glucan
chitin
does not exist in humans
drugs targeting these: Echinocandins

Answer 189

A

containing ergosterol
human cell membrane contains cholesterol NOT ergosterol
drugs targeting these: Amphotericin, Azoles and Terbinafine

Answer 190

A

ergosterol

Answer 191

A

a compound that is able to act as a base and an acid

Answer 192

A

amphotericin B

Answer 193

A

drugs used to treat fungal infections
e.g. Amphotericin B
cause pore formation in ergosterol containing membranes
fungicidal

Answer 194

A

it has 10 times lower affinity for cholesterol in mammalian

membranes

Answer 195

A

nephrotoxicity - dose dependent; usually reversible
distal renal tubular acidosis (hypokalaemia)
can cause hyperkalaemia if infused rapidly resulting in cellular damage
also causes infusion related; chills/rigors/hypotension and
acute anaphylactoid reactions

Answer 196

A

causes the reversible inhibition of squalene epoxidase (an enzyme required for growth of the fungi)
it’s a fungicidal

Answer 197

A

Terbinafine

Answer 198

A

it is well absorbed but undergoes extensive first pass metabolism resulting in a bioavailability of only 45%
distributes extensively to poorly perfused sites such as the skin and nail beds (common sites of fungal infection)
primarily used against Candida and Aspergillus

Answer 199

A

well tolerated and only results in taste disturbance and deranged liver function tests (LFT)
it does result in increased CYP450 metabolism but this is by multiple enzymes and is minimally inhibitory

Answer 200

A

dose-dependent inhibitors of 14a-sterol demethylase - an important intermediate in the pathway of cholesterol (human) and ergosterol (fungi) production
it’s a fungistatic

Answer 201

A

• clotrimazole and ketoconazole is active against Candida
• fluconazole is active against Cryptococcus
• itraconazole is active against Aspergillus and dimorphics such as
Coccidiodes and Sporothrix

Answer 202

A

clotrimazole and ketoconazole

Answer 203

A

fluconazole

Answer 204

A

itraconazole

Answer 205

A

relatively safe
all associated with transaminitis (elevated transaminases in liver) and GI side effects
rare to cause severe hepatitis
alopecia with long term fluconazole
GI symptoms are more pronounced with itraconazole:
• nausea, abdominal pain and diarrhoea
• rare life threatening liver failure

Answer 206

A

hydrophilic and excreted unchanged

* less significant interactions with: warfarin, anxiolytics and calcineurin inhibitors

Answer 207

A

• a potent CYP3A4 inhibitor
• interactions with:
- less significant interactions with: warfarin, anxiolytics and calcineurin inhibitors
- steroids
- statins

Answer 208

A

multiple mechanism in Candida

- fluconazole and voriconazole most affected

Answer 209

A

inhibit 1,3 B glucan synthase - interferes with fungal cell wall synthesis
is fungicidal to susceptible yeasts
is fungistatic to moulds
has activity against mould but not yeast forms of dimorphics

Answer 210

A

some fungi genera that do not have large amounts of 1,3 B glucan in their cell wall are intrinsically resistant to this drug class:

Crytococcus
Zygomycetes
Trichosporon
limited activity against Scedosporium

Answer 211

A

has poor oral bioavailability thus IV only
has poor penetration into the CSF, eye and urine
few drug interactions

Answer 212

A

rare type-1 hypersensitivity
hepatotoxicity
hypokalaemia

Answer 213

A

Amphotericin B, Nystatin
binds to sterols and destabilises cell membrane
used in systemic and topical disease

Answer 214

A

clotrimazole, miconazole, ketoconazole, fluconazole, itraconazole, voriconazole, posaconazole
inhibits ergosterol biosynthesis
used in topical and systemic disease

Answer 215

A

terbinafine
inhibit ergosterol biosynthesis
used in superficial infections, including onychomycosis

Answer 216

A

caspofungin, anidulafungin, micafungin
inhibit the formation of cell wall glucan
used in systemic disease

Answer 217

A

5-fluorocytosine
inhibit DNA and RNA synthesis
used in systemic disease

Answer 218

A

griseofulvin
inhibits microtubule assembly
used in topical disease

Answer 219

A

blood cultures are only half as sensitive for fungi as for bacteria
it’s better to pick-up from tissue/fluids:
• if cultured properly
• if these samples can be obtained

Answer 220

A

pretty much all Candida are sensitive to Echinocandins

- pretty much all Candida are sensitive to Amphotericin B

Answer 221

A

the cell wall component of many fungi including common ascomycetous pathogens and pneumocystis
released into serum during invasive infection

Answer 222

A

fungal nail infection; very common

Answer 223

A

caused by dermatophyte moulds:
• grow best at about 30 degrees
Trichophyton rubrum is the most common cause

Answer 224

A

microscopy is most specific, but 30% of the culture is negative

Answer 225

A

psoriasis
lichen planus
trauma
eczema
malignant melanoma

Answer 226

A

results of sampling can be confusing
limited treatment options:
• topical amorolfine
• systemic itraconazole or terbinafine
treatment takes ages
high failure rate with all therapies

Answer 227

A

infection/colonisation of health people is frequent and occurs early in life
disease develops only with moderate-severe immunocompromised
especially in HIV, transplant and steroids
think pneumocystis when a patient has hypoxia that is more severe than the chest x-ray would suggest - especially with gradual onset or risk
factors

Answer 228

A

Co-trimoxazole
Clindamycin
Pentamidine
Trimetrexate

Answer 229

A

M. tuberculosis; tuberculosis
M. leprae; leprosy
M.avium complex (MAC); disseminated infections in AIDS, infections in patients with chronic lung disease
M. kansasii - chronic lung infection
M. marinum - fish tank granuloma
M. ulcerans - Buruli ulcer

Answer 230

A

Mycobacterium tuberculosis

Answer 231

A

M. leprae

Answer 232

A

M. avium complex

Answer 233

A

M. kansasii

Answer 234

A

M. marinum

Answer 235

A

M. ulcerans

Answer 236

A

aerobic
have resistance to destaining by acid and alcohol
may cause meningitis - tuberculosis meningitis
can withstand phagolysosomal killing
non-spore formin
non-motile bacillus/rods
high cell wall content of high molecular weight lipids
slow growing
cell wall key components

Answer 237

A

weakly gram-positive or colourless - it difficult to stain mycobacteria since they have a thick cell wall that doesn’t take up stain easily
cell wall contains lipoarabinomannan
survives inside macrophages, even in low pH environments
mycolic acids and liporabinomannan - make up strong waxy cell wall that is hard for the immune system to target/damage

Answer 238

A

M. tuberculosis generation time 15-20 hours compared to 1 hour for common bacterial pathogens
slow growth means its difficult for antibiotics to target the division phase of the mycobacteria

Answer 239

A

bacteria should be found in all people with disease
bacteria should be isolated from the infected lesions in people with the disease
a pure culture inoculated into a susceptible person should produce symptoms of the disease
the same bacteria should be isolated from the intentionally infected individual

Answer 240

A

high lipid content with mycolic acids in cell wall makes Mycobacteria resistant to Gram stain
slightly curved, beaded bacilli/rods

Answer 241

A

red/pink (positive for acid-fast)

Answer 242

A

nucleic acid amplification using PCR
produces rapid result for mycobacterium tuberculosis
highly sensitive and specific test
recommended for the rapid diagnosis in TB endemic countries

Answer 243

A

Mycobacteria are acid fast bacilli that are phagocytosed by macrophages and are placed in a phagolysosome within the macrophage
the bacteria has adapted to the intracellular environment and aims to withstand phagolysosomal killing and escape to the cytosol - primarily through the presence of their thick waxy cell wall
the host aims to kill the mycobacterium using microbicidal molecules
acidification aids digestion and degradation by proteases of the mycobacteria which results in the generation of antigens for presentation
to T-cells

Answer 244

A

effective immunity requires CD4 T-cells which generate interferon gamma and this helps activate intracellular killing by macrophages
IL-12 release by macrophages further stimulates the generation of T helper cells and interferon gamma release
genetic defects in interferon gamma or IL-12 receptors or elements of their signalling pathways result in susceptibility to mycobacterial infection

Answer 245

A

granuloma are lesions the arise in a response that tries to contain mycobacteria (but also occur in other infections and non-infectious
processes):
• highly stimulated macrophages become epithelioid cells
• some macrophages fuse with each other to form giant multinucleate cells “Langhans giant cells”
• T cells including cytotoxic CD8 T-cells infiltrate the granuloma

Answer 246

A

a granuloma prevents nutrients from entering - thereby starving the mycobacteria:
• TB will go into a dormant state when inside the granuloma
• can reactivate at some point in the future when conditions are better

Answer 247

A

the highly immunogenic nature of mycobacterial lipids stimulate T-cell responses 3-9 weeks after exposure to M. tuberculosis

Answer 248

A

macrophage killing of mycobacteria, containment of

infection, formation of a tissue granuloma

Answer 249

A

hypersensitivity reactions (type 4) with skin lesions, eye lesions and swelling of joints

Answer 250

A

this reactivity can be measured in the tuberculin skin test where intradermal injection of purified protein derivatives induce skin swelling and redness
it can also be measured in interferon gamma release assays

Answer 251

A

use antigens specific to M. tuberculosis e.g. ESAT-60 and CFP10 to distinguish between this and BCG vaccine or environmental mycobacteria
IGRAs demonstrate exposure to M.tuberculosis but not active infection

Answer 252

A

slowly replicating bacteria so need prolonged treatment - 6 months of antimicrobials
there are different populations of mycobacteria in particular locations
intracellularly and extracellularly or in environments of differing pH
resistance may emerge on treatment so use multi-drug combinations to ensure target all populations and mutants
compliance is essential; directly observed treatment used for many patient groups to ensure success

Answer 253

A

Isoniazid (INH), Rifampicin (RIF), Pyrazinamide (PZA), Ethambutol (ETH) for two months
Isoniazid and rifampicin for further 4 months

Answer 254

A

fluroquinolones
injectable agents such as; streptomycin, cyclosporine and capreomycin
prothionamide

Answer 255

A

hepatotoxicity - Isoniazid, rifampicin, pyrazinamide
peripheral neuropathy with isoniazid - give vitamin B6 to protect against this
optic neuritis - ethambutol

Answer 256

A

bacilli settle in apex (top part near shoulders) and granuloma forms
bacilli taken in lymphatics to hilar lymph nodes
in apex of lungs there is more air and less blood supply thus fewer defending white cells to fight off infection

Answer 257

A

granuloma + lymphatics + lymph nodes

Answer 258

A

cell mediated immune (CMI) response from T-cells

* primary infection is contained but CMI persists

Answer 259

A

no clinical disease (normal chest x-ray)

* detectable CMI to TB on tuberculin skin test of IGRA

Answer 260

A

could occur immediately following primary disease (post-primary) or after latent reactivation
cell mediated immune (CMI) response from T-cells
necrosis in lesion
caseous material coughed up leaving cavity
TB may spread in lung causing other lesions
CMI and caseation in lesion results in cavity

Answer 261

A

bacilli can spread from apex to hilar lymph nodes and then elsewhere

Answer 262

A

TB meningitis
miliary TB (widespread dissemination and tiny spotted lesions all over lungs and elsewhere)
pleural TB
bone and joint TB
genitourinary TB

Answer 263

A

nematodes (roundworms)
trematodes (flatworms, flukes)
cestodes (tapeworms)

Answer 264

A

intestinal
Larva migrans
tissue (filaria)

Answer 265

A

blood
liver
lung
intestinal

Answer 266

A

non-invasive

* invasive

Answer 267

A

rare in UK - most cases are imported
adult worms cannot usually reproduce without a period of development outside the body - worm cannot replicate inside body, so if it cannot get out it will eventually die
thus, although they usually produce innumerable larvae or eggs (which may themselves cause disease), the total worm burden cannot increase without constant re-exposure to infection

Answer 268

A

the interval between infection and the appearance of eggs in the stool

Answer 269

A

single-celled eukaryotic organisms with a definitive nucleus
eaten by invertebrates
important parasitic and symbiotic relationships

Answer 270

A

consumers of bacteria, algae and microfungi

Answer 271

A

all eat food by phagocytosis and then digest it in intracellular vacuoles

Answer 272

A

in aqueous environments and the soil

Answer 273

A

type of protozoa
flagellum as main locomotory organelle
usually reproduce by binary fission

Answer 274

A

intestinal flagellates
haemoflagellates
other body sites

Answer 275

A

Giardia lamblia

Answer 276

A

7-day business trip to Delhi 2 months ago
loose stools on last day of stay in India
ongoing offensive diarrhoea daily since return to UK
flatulence, abdominal cramps

Answer 277

A

Trypanosoma spp.

Answer 278

A

also known as ‘sleeping sickness’
bitten on arm by insect; lesion developed 2 weeks
later > self-resolved
2 years later he gets fever, lethargy and myalgia
excessive weight loss
personality change
irritability
increasing daytime tiredness
coma
the West African strain is more severe compared to
the more endemic East African strain

Answer 279

A

amoebae

- move by means of flowing cytoplasm and production of pseudopodia

Answer 280

A

Entanomoeba histolytica

Answer 281

A

2-month visit to rural Botswana
bloody diarrhoea
on return to UK, increasing right upper quadrant pain
CT shows liver abscess

Answer 282

A

sporozoans
no locomotory extensions
all species are parasitic
most are intracellular parasites
reproduce by multiple fission

Answer 283

A

malaria: Plasmodium spp.

- other: Cryptosporidium spp. and Toxoplasma gondii

Answer 284

A

recent HIV positive diagnosis: CD4 count: 70 (below 450 = low and below 100 = high risk of AIDs)
2-week history of progressive left sided weakness
headaches and visual disturbances
commonly presents when people are
immunosuppressed e.g. HIV/AIDs or cancer on chemotherapy

Answer 285

A

ciliates
very large group
have cilia that beat rhythmically at some stage in lifecycle
two types of nuclei (macronucleus and micronucleus)

Answer 286

A

Balantidium coli - presents mainly in those who are
immunocompromised
- causes severe diarrhoea and/or ulceration of colon

Answer 287

A

very small
production of resistant spores
causes diarrhoea in immunocompromised

Answer 288

A

Enterocytozoon bieneusi

Answer 289

A

mastigophora (flagellates)
sarcodina (ameobae)
apicomplexa (sporozoans)
ciliophora (ciliates)
microsporidia

Answer 290

A

protozoan infection caused by Plasmodia spp..

Answer 291

A

4 species cause human disease:
• P. falciparum (most common)
• P. ovale
• P. vivax
• P. malariae

Answer 292

A

transmitted by the bite of the female anopheles mosquito

Answer 293

A

300-500 million cases per year (80% Africa)
700,000 - 2.7 million deaths a year (more than 90% African)
cause of 50% of fever in African children under 5
50% of world population at risk

Answer 294

A

increasing resistance of parasite to antimalarials
increased resistance of mosquito to insecticides
ecological and climate changes - means mosquitoes can be found in more countries
increased travel to endemic areas

Answer 295

A

female anopheles mosquito; mainly bites at night

Answer 296

A

worldwide distribution

Answer 297

A

infection is acquired during feeding from infected human

* mosquito is infected for life

Answer 298

A

3-4 weeks

Answer 299

A

night biting
mainly bites indoors
lifecycle depends on water

Answer 300

A

plasmodia lifecycle has stages in human and mosquito host

* variation in lifecycle between different Plasmodia spp. results in different clinical manifestations

Answer 301

A

the female anopheles mosquito becomes infected after taking a blood meal containing gametocytes, the sexual form of the malarial parasite

Answer 302

A

the developmental cycle in the mosquito usually takes 7-20 days (depending on temperature) culminating in the migration of infective sporozoites to the insect’s salivary glands

Answer 303

A

infection of parasite (female anophales mosquito)
multiplication in liver
invasion and multiplication in RBCs
formation of gametocytes
completion of gametogony
migration of sporozoites to mosquito salivary gland

Answer 304

A

the sporozoites are inoculated into a new human host and those not destroyed by the immune system are rapidly taken up by the liver
here they multiply inside hepatocytes as merozoites; this is the pre-erythrocytic (or hepatic) sporogeny

Answer 305

A

the sporozoites are inoculated into a new human host and those not destroyed by the immune system are rapidly taken up by the liver
here they multiply inside hepatocytes as merozoites; this is the pre-erythrocytic (or hepatic) sporogeny

Answer 306

A

after a few days, the infected hepatocytes rupture, releasing merozoites into the blood, from where they are rapidly taken up by erythrocytes

Answer 307

A

in the case of P. vivax and P. ovale, a few parasites remain dormant in the liver as hypnozoites - these may reactivate at any time subsequently, causing relapsing infection - this is why its important to ask a 2 year travel history to counter P.vivax and P.ovale
can remember by OVO - Ovale Vivax Overstay
also note due to the dormancy the hypnozoites will not be eradicated by conventional antimalarials

Answer 308

A

Ovale Vivax Overstay

these parasites can become hypnozoites and remain dormant in the liver
won’t be eradicated by conventional antimalarials

Answer 309

A

• inside the red cells, the parasites again multiply, changing from merozoites to trophozoites to schizonts and finally appearing as 8-24
new merozoites
• the erythrocyte ruptures, releasing the merozoites to infect further cells

this is erythrocytic schizogony

Answer 310

A

• inside the red cells, the parasites again multiply, changing from merozoites to trophozoites to schizonts and finally appearing as 8-24
new merozoites
• the erythrocyte ruptures, releasing the merozoites to infect further cells

Answer 311

A

each cycle of this process, which is called erythrocytic schizogony, takes about 48 hours in P. falciparum, P. vivax and P.ovale disease
whereas in P. malariae it takes 72 hours

Answer 312

A

mainly reticulocytes and young erythrocytes

Answer 313

A

tends to attack older cells

Answer 314

A

parasitises any stage of erythrocyte

Answer 315

A

trophozoites or gametocytes

Answer 316

A

develop from merozoites

- not released from red cells until they are taken up by a feeding mosquito to complete the life cycle

Answer 317

A

sporozoites -> merozoites -> trophozoites -> schizonts -> merozoites

Answer 318

A

pathology is related to anaemia, cytokine release and in the case of P. falciparum, widespread organ damage due to impaired microcirculation

Answer 319

A

haemolysis of infected red cells
haemolysis of non-infected red cells (Blackwater fever - when malaria is left to go untreated; results in dark coloured urine)
splenomegaly
folate depletion

Answer 320

A

red cells contains schizonts adhere to the lining of capillaries in the brain, kidneys, gut, liver and other organs
as well as causing mechanical obstruction, these schizonts can rupture, releasing toxins and stimulating further cytokine release

Answer 321

A

10-21 days

Answer 322

A

• very varied
• fever is common (but not always present)
• other common features:
- chills and sweats
- headache
- myalgia
- fatigue
- nausea and vomiting
- diarrhoea

Answer 323

A

in any febrile individual who has resided in or travelled to an endemic area

Answer 324

A

illness is usually relatively mild
although P. vivax can occasionally cause severe disease
anaemia develops slowly and there may be tender
hepatosplenomegaly
spontaneous recovery usually occurs within 2-6 weeks but
hypnozoites in the liver can cause relapses for many years
after infection
repeated infections often cause chronic ill health due to
anaemia and hyper-reactive splenomegaly

Answer 325

A

this causes a relatively mild illness but tends to run a more
chronic course
parasitaemia (parasites in blood) may persist for years, with or without symptoms
in children, P.malariae infection is associated with
glomerulonephritis and nephrotic syndrome

Answer 326

A

P. falciparum

Answer 327

A

causes a self-limiting illness similar to the other types of
malaria
it may cause serious complications and the vast majority of deaths are due to P. falciparum
patients can deteriorate rapidly, and children in particular progress from reasonable health to coma and death within hours
a high parasitaemia (more than 1% of red cells infected) is an indicator of severe disease
cerebral
blackwater fever

Answer 328

A

shock

- hypotensive (<80 systolic and Gram-negative septicaemia)

Answer 329

A

hypoglycaemia (<2mmol/L)

- metabolic acidosis

Answer 330

A

prostration

- cerebral malaria

Answer 331

A

retinal haemorrhages

Answer 332

A

tachypnoea

- acute respiratory distress syndrome

Answer 333

A

severe anaemia (haemolysis and dyserythropoiesis)
DIC
bleeding

Answer 334

A

haemoglobuinuria
oliguria
uraemia

Answer 335

A

diarrhoea
jaundice
splenic rupture

Answer 336

A

- cerebral malaria is
marked by diminished
consciousness, confusion and
convulsions progressing
to coma and death 
- due to the reduced brain
perfusion caused by schizonts adhering to the endothelial cells of capillaries = hypoxia to brain

Answer 337

A

widespread intravascular haemolysis, affecting both parasitised and unparasitised red cells, giving rise to dark urine

Answer 338

A

coma
acute respiratory distress syndrome (ARDS)
anaemia
jaundice
hepatosplenomegaly
hypoglycaemia - since parasites eat up glucose (pregnant women especially susceptible)
blackwater fever
renal failure due to hypovolaemia and microvascular blockade due to the schizonts
shock secondary to bacterial sepsis

Answer 339

A

non-specific; they stop crying, playing and eating
tachypnoea - rapid breathing
anaemia
hypoglycaemia
cerebral malaria
raised intracranial pressure
convulsions (60-80%)
rule out meningitis

Answer 340

A

anaemia
low platelets
hyperbilirubinaemia
mildly raised transaminases (ALT, AST)

Answer 341

A

thick and thin

- do films at least 12hrs apart to check for presence

Answer 342

A

• sensitive but low resolution (difficult to interpret and
speciate the parasite but has a higher yield)
• tells you is malaria is present

Answer 343

A

• can identify morphological features and quantification of
parasitaemia
• tells you type and parasite count, above 2% = severe
• trophozoite most commonly used

Answer 344

A

3 separate films should be examined before malaria is declared unlikely

Answer 345

A

extreme weakness (e.g. inability to walk or sit)
impaired consciousness - hypoglycaemia
parasite count greater than 2%
spontaneous bleeding/disseminated intravascular coagulation
haemoglobinuria
renal impairment or electrolyte/acid-base disturbance (pH less than 7.3)
pulmonary oedema or adult respiratory distress syndrome
shock

Answer 346

A

IV artesunate (gold standard)

* or IV quinine (second best since it causes hypoglycaemia so monitor sugar levels)

Answer 347

A

oral riamet
or oral quinine
add doxycycline as 2nd agent to treat undiscovered/untreated
malaria

Answer 348

A

oral chloroquine

Answer 349

A

primaquine for hypnozoite clearance

- check G6PD (G6PD deficiency) and pregnancy status since not suitable for these individuals

Answer 350

A

most common imported tropical disease in UK
around 75% are falciparum
mixed infections
commonly presents ‘atypically’ e.g no fever
in pregnancy is severe

Answer 351

A

sickle cell trait gives protection against malaria
Glucose-6-phosphate dehydrogenase deficiency (G6PD) - G6PD is an enzyme that is essential for assuring the normal lifespan for red blood cells, deficiency results in the sudden destruction of red blood cells and can lead to haemolytic anaemia - malaria parasites cannot survive in these red cells
Thalaessaemias confer protection against malaria

Answer 352

A

recurrent infection can result in semi-immunity but this is lost if not reinfected after a couple of years
maternal transmission of antibodies across the placenta, but this diminishes over time

Answer 353

A

dengue and viruses
malaria and protozoa
trypanosomes and leishmaniasis
helminths/worms

Answer 354

A

hookworm, ascaris

- Buruli Ulcer

Answer 355

A

amoebae, giardia

- typhoid, bacteria

Answer 356

A

the most common arthropod-borne viral infection in humans; over 100 million cases occur every year in the tropics, with over 10,000 deaths from dengue haemorrhagic fever
disease is endemic in all tropical regions including norther Australia, most South-east Asian countries, tropical Africa and the Middle East and Caribbean countries
cases of dengue are also imported into the continental USA and Europe (e.g. Italy) via tourists returning from endemic countries

Answer 357

A

dengue fever

Answer 358

A

flavovirus

Answer 359

A

transmitted by the Aedes mosquito which is daytime-biting - breeds in standing water in refuse dumps in inner cities

Answer 360

A

humans are infective during the first 3 days of illness
mosquitoes become infective about 2 weeks after feeding on an infected
individual and remain so for life

Answer 361

A

incubation is 5-6 days following the mosquito bite

Answer 362

A

fever
malaise
headache
facial flushing
retrobulbar pain (behind eyes)
severe backache

Answer 363

A

fever subsides after 3-4 days, the temperature returns to normal for a couple of days and then the fever RETURNS,
together with the above features but milder
severe fatigue, a feeling of being unwell and depression are common several weeks after the fever has subsided

Answer 364

A

a severe form of dengue fever and believed to be the result of two or more sequential infections with different dengue serotypes

Answer 365

A

capillary leak syndrome
thrombocytopenia (low platelet count)
haemorrhage
hypotension
shock

Answer 366

A

characteristically a disease of children, occurring most

commonly in South-east Asia

Answer 367

A

mild start, often with symptoms of an upper respiratory tract infection

Answer 368

A

shock
haemorrhage into the skin and ear
bleeding from nose (epistaxis)
haematemesis (vomiting blood)
meleana (bloody stools)
all collectively known as dengue shock syndrome

Answer 369

A

isolation of dengue virus by tissue culture, or detection of viral RNA by PCR in sera obtained during the first few days of illness - diagnostic
detection of virus-specific IgM antibodies, or of rising IgG titres in sequential serum samples

Answer 370

A

supportive with analgesics and adequate fluid replacement

* in DHF, blood transfusion may be necessary as well as intensive care support

Answer 371

A

about 20-220nm diameter
only visualised by electron microscopy
in comparison staphylococci bacteria are about 1 micrometer in diameter

Answer 372

A

grow only inside living cells

Answer 373

A

when diagnosing viral infections samples do not need to come from sterile sites since there are no commensal viruses to confuse with

Answer 374

A

posses only one type of nucleic acid, RNA or DNA

Answer 375

A

posses only one type of nucleic acid, RNA or DNA
no cell wall structure but have an outer protein coat surrounded in some viruses by a lipid envelope (contains viral proteins and lipids)
essentially inert outside the host cell, but carry proteins that function as enzymes inside the cell
proteins on virus surface allow attachment to complementary receptors on susceptible host cell plasma membrane

Answer 376

A

takeover protein manufacture in order to replicate itself

Answer 377

A

attachment
cell entry
interaction with host cells
replication
assembly
release

Answer 378

A

viral and cell receptors e.g. HIV (gp120 on HIV and CD4 on T cell)

Answer 379

A

only the viral ‘core’ which carries the nucleic acid and some associated proteins acting as enzymes for replication and negation of intracellular host defence factors are freed into the host cell cytoplasm
outer protein coat does not enter

Answer 380

A

virus uses cell materials (enzymes, amino acids, nucleotides) for their own replication
also need to subvert host cell defences

Answer 381

A

production of progeny viral nucleic acid and viral proteins in nucleus, cytoplasm or both

Answer 382

A

can occur in nucleus e.g. herpesvirus
can occur in cytoplasm e.g. polio virus
can occur in cell membrane e.g. influenza virus

Answer 383

A

by bursting open (lysis) of cell e.g. rhinovirus
by ‘leaking’ (exocytosis) from the cell overtime e.g. HIV & influenza virus (2-3 days from upper respiratory tract)
only a few virus particles will enter the host but millions will exit due to replication

Answer 384

A

in most viral disease, more than one damage-inducing mechanism operates
some host-derived immunopathological damage occurs in most visual infections

Answer 385

A

damage by direct destruction of host cells e.g. polio, influenza (respiratory cells) and HIV (immune cells
damage by modification of host cell structure or function
damage involving over-reactivity of the host as a response to infection - immunopathological damage e.g. hep B and C and HIV
damage through cell proliferation and cell immortalisation (cancer) e.g. human papillomavirus (HPVs):
evasion of both extracellular and intracellular host defences

Answer 386

A

polio virus
influenza (respiratory cells)
HIV (immune cells)

Answer 387

A

3 types but type 1 is the most severe
controlled by vaccination, enters body orally then invades and replicates in the gut then travels in the bloodstream and targets
the brain where it results in direct brain cell destruction
once infection reaches the brain in unimmunised person it’s very difficult to deal with and can result in paralysis
by the time an immune response is in effect, the virus has already caused damage

Answer 388

A

physical modification e.g. rotavirus or HIV

* functional modification e.g. rotavirus, respiratory syncytial virus (RSV) and HIV

Answer 389

A

rotavirus or HIV

Answer 390

A

rotavirus, respiratory syncytial virus and HIV

Answer 391

A

following ingestion, rotavirus infects epithelial cells of the small intestine, mainly in the jejunum (rotavirus are resistant to acid pH)
histologically, there is shortening and atrophy of the villi, flattening of the epithelial cells and stripping of the microvilli - decreasing the surface areas of the small intestine
this limits the production of digestive enzymes such as the disaccharides, normally synthesised by the cells of the brush border
the patient suffers a malabsorptive state in which dietary nutrients such as sugars are not absorbed by the small intestine
this results in hyperosmotic effects causing profuse diarrhoea

Answer 392

A

fluid replacement therapy can usually solve the problem
if caught early its easily treatable
if caught late there good by some long term problems

Answer 393

A

hep B and C, and HIV

Answer 394

A

the majority of HBV infection are asymptomatic
both HBV and hepatitis C are spread by blood or sexual contact
following symptomatic HBV infection there are massive
antibody and cell mediated immune (CMI) responses that
destroy many virally infected hepatocytes
this results in extensive liver damage resulting in jaundice
during acute infection, large numbers of infectious HBV
particles are produced
if you recover (most do) then you will be a carrier and 80% will be asymptomatic

Answer 395

A

blood or sexual contact

Answer 396

A

in a HBV carrier there is a steady-state between virus

replication in host cells and the host defence responses

Answer 397

A

limited but sustained viral replication
natural hepatocyte regeneration
proliferation of hepatocytes due to the oncogenic properties of HBV
liver cell destruction by CD8+ T cells that recognise
HBV proteins on the hepatocyte surface as ‘foreign’
no clinical symptoms but HBV particles circulate in the patients bloodstream

Answer 398

A

causes plantar warts

- can result in cancers, particularly those of the cervix

Answer 399

A

has no envelope compared to influenza, hepatitis B or C
very small
there are 70-80 different viruses, only type 16 and 18 have oncogenic potential in humans

Answer 400

A

16 and 18

Answer 401

A

HPV 16 and 18 are responsible for cervical carcinoma

* result of HPV infection of supra basal layer in genital tract

Answer 402

A

• once in the supra basal layer, the virus may partially
replicate including transcription and expression of several early viral gene products
• at some point the HPV genome may become integrated into the host cell chromosome
• following integration, control of viral gene expression by the HPV E2 protein is lost and the HPV E6 and E7 proteins
may be expressed
• when expressed, the HPV E6 and E7 proteins prevent the operation of two cell growth and proliferation suppressor proteins - Retinoblastoma (Rb) and p53
• excessive cell growth and proliferation occurs and
cervical cell carcinoma can result

Answer 403

A

• following integration, control of viral gene expression by the HPV E2 protein is lost and the HPV E6 and E7 proteins
may be expressed
• when expressed, the HPV E6 and E7 proteins prevent the operation of two cell growth and proliferation suppressor proteins - Retinoblastoma (Rb) and p53

Answer 404

A

virus persistence
virus variability
variation of antigens
persistence or latency
cell to cell spread
antigenic variability
prevention of host cell apoptosis
down regulation of interferon and other intracellular host defence proteins; most viruses do this
interference with host cell antigen processing pathways

Answer 405

A

Herpes viruses (survive throughout lifetime)
Hepatitis B and C viruses
measles virus
HIV

Answer 406

A

influenza (mutates yearly - a vaccine that works one year will be less effective the next year)
HIV
Hepatitis C virus
rhinovirus

Answer 407

A

persistence or latency

- cell to cell spread

Answer 408

A

all herpes viruses (HSV- 1 and 2)
Varicella-zoster virus (VZV)
Epstein-barr virus (EBV) - causes glandular fever,
remains latent in B cells meaning you carry virus for
rest of life and can transmit via oral secretions

Answer 409

A

measles virus

- HIV

Answer 410

A

influenza type A virus
HIV
Rhinovirus

Answer 411

A

Herpes virus
HIV
since host cell defence mechanism is to destroy
itself, the virus releases proteins to prevent this and
is thus able to continue to replicate

Answer 412

A

Herpes virus
Measles virus
HIV

Answer 413

A

variation through the formation of ‘quasi-species’ e.g. HIV and hepatitis C virus
variation through gene re-assortment and mutation e.g.
Influenza A viruses and HIV
variation through many stable serotypes e.g. rhinoviruses - about 110 different cold viruses

Answer 414

A

hand hygiene!

Answer 415

A

Carbapenemase producing Enterobacteriaceae

- also known as coliforms - standard gut germs

Answer 416

A

E.coli
Klebsiella
Serratia
Enterobacter

Answer 417

A

colonisers of the large bowel, skin below waist and moist sites
the most common causes of UTI and intra-abdominal infection
occasional respiratory tract infection and skin and soft tissue infection
in the past, the vast majority of these germs were susceptible to the
antibiotics that we currently use with gram negative infection

Answer 418

A

these are the broadest spectrum beta-lactam antibiotics available

Answer 419

A

they have moved from being rarely used last resort antibiotics to frequently used second-line agents and even first-line therapy for patients with severe sepsis; this is because resistance of gram negatives to other agents like cephalosporins and piperacillin-tazobactam has
increased

Answer 420

A

hydrolyse carbapenems and other beta-lactams

- confer resistance to the entire class of antibiotic

Answer 421

A

agents produced by micro-organisms that kill or inhibit the growth of other micro-organisms in high-dilution

Answer 422

A

penicillin

Answer 423

A

semi-synthetic derivatives of antimicrobials

Answer 424

A

antibiotics are molecules that work by binding a target site on a bacteria:
- defined as points of biochemical reaction crucial to the survival of the
bacterium
- the crucial binding site will vary with the antimicrobial class

Answer 425

A

defined as points of biochemical reaction crucial to the survival of the bacterium

Answer 426

A

Beta lactams (penicillins and cephalosporins) glycopeptides
Metronidazole and Rifampicin
Fluroquinolones
Aminoglycosides, Tetracyclines, Macrolides
and Chloramphenicol
Sulphonamides and Trimethoprim

Answer 427

A

these bind to bacterial cell wall and result in the inhibition of cell wall synthesis e.g. penicillin binding proteins on bacteria surface

Answer 428

A

interfere with nucleic acid synthesis or function

Answer 429

A

inhibit DNA gyrase (essential for bacterial DNA replication)

Answer 430

A

inhibit ribosomal activity and protein synthesis

Answer 431

A

inhibit folate synthesis - required for bacteria to grow since folic acid cannot cross the bacteria cell wall

Answer 432

A

beta lactams (penicillins and cephalosporins) glycopeptides

Answer 433

A

metronidazole and rifampicin

Answer 434

A

fluroquinolones

Answer 435

A

aminoglycosides, tetracyclines, macrolides and chloramphenicol

Answer 436

A

sulphonamides and trimethoprim

Answer 437

A

prevent the growth of bacteria but not necessarily kill it
however in more than 90% they kill in 18-24 hours
antibiotics that inhibit protein synthesis, DNA replication or metabolism are bacteriostatic

Answer 438

A

these agents kill the bacteria
they kill more than 99% in 18-24 hours
antibiotics that generally inhibit cell wall synthesis
useful if there is poor penetration e.g. endocarditis or difficult to treat infections or need to eradicate infection quickly e.g. meningitis

Answer 439

A

the drug must not only attach to its binding target but also must occupy an adequate number of binding sites, which is related to its concentration within the microorganism
to work effectively, the antimicrobial should remain at the binding site for a sufficient period of time in order for the metabolic processes of the bacteria to be sufficiently inhibited
must reach and stay at the site of bacterial infection

Answer 440

A

concentration and the time that the antimicrobial remains on the binding sites

Answer 441

A

the ‘knockout punch’

* key parameter is how high the concentration is above the MIC

Answer 442

A

aminoglycosides

- quinolones

Answer 443

A

sustained killing

* key parameter is the time that serum concentrations remain above the MIC during the dosing interval

Answer 444

A

beta-lactams (penicillins, cephalosporins, carbapenems, monobactams)
clindamycin
macrolides (erythromycin, darithromeycin)
oxazolidinones (linezolid)

Answer 445

A

pharmokinetics - movement of a drug from its administration site to the
place of its pharmacologic activity and its elimination from the body:
- release from the dosage form
- absorption from the site of administration into the bloodstream
- distribution to various parts of the body, including the site of action
- rate of elimination from the body via metabolism (liver) or
excretion (kidney) of unchanged drug

Answer 446

A

site of infection

- what antibiotics are safe for the patient

Answer 447

A

which antibiotics will penetrate that site?
what is the pH of the site?
is the antibiotics lipid soluble?

Answer 448

A

intolerance, allergy and anaphylaxis
side effects
age
renal and liver function
pregnancy and breast feeding
drug interactions
risk of clostridium difficile (antibiotic induced diarrhoea)

Answer 449

A

Ciprofloxacin
Clindamycin
Cephalosporins
Co-amoxiclav (augmentin)
Carbapanems e.g. meropenem

Answer 450

A

target site mutation
destruction of antibiotic
prevention of antibiotic entry
remove antibiotic from bacterium

Answer 451

A

bacteria changes the molecular configuration of its antibiotic binding site or masks it:
- flucloxacillin (or methicillin) is no longer able to bind
penicillin binding protein of Staphylococci in MRSA
- wall components change in enterococci and reduce
vancomycin binding - vancomycin-resistant enterococci

Answer 452

A

the antibiotic is destroyed or inactivated:

beta lactam ring of penicillins and cephalosporins can be hydrolysed by bacterial enzyme ‘beta lactamase’ meaning they are unable to bind to penicillin binding proteins and inhibit cell wall synthesis
Staphylococci produce penicillinase so penicillin but not flucloxacillin is inactivated

Answer 453

A

their beta lactam ring can be hydrolysed by bacterial enzyme beta lactamase, meaning they’re unable to bind penicillin binding proteins and inhibit cell wall synthesis

Answer 454

A

they produce penicillinase, so penicillin but not flucloxacillin is inactivated

Answer 455

A

bacteria modifies its bacterial membrane porin channel size, numbers or selectivity

Answer 456

A

proteins in bacterial membranes can act as an export or efflux pump so the antibiotic is pumped out of the bacteria/microbe resulting in reduced levels and thus effect of antibiotic on bacteria/microbe:

S.aureus or S.pnuemoniae resistance to fluroquinolones
Enterobacteriacae resistance to tetracyclines

Answer 457

A

proteins act as an efflux pump so the antibiotic is pumped out, thus reducing the levels and effect of the antibiotic

Answer 458

A

proteins act as an efflux pump so the antibiotic is pumped out, thus reducing the levels and effect of the antibiotic

Answer 459

A

all subpopulation of a species will be equally resistant

Answer 460

A

aerobic bacteria are unable to reduce metronidazole to its
active form thus the antibiotic is harmless to them
anaerobic bacteria lack oxidative metabolism required to take up aminoglycosides
vancomycin is not taken up by gram negative bacteria - it
cannot penetrate their outer membrane since its too large

Answer 461

A

unable to reduce it to its active form

Answer 462

A

lack oxidative metabolism to take them up

Answer 463

A

cannot penetrate their outer membrane since it is too large

Answer 464

A

a bacterium which was previously susceptible obtains the ability to resist the activity of a particular antibiotic
only certain strains or subpopulations of a species will be resistant

Answer 465

A

spontaneous gene mutation

- horizontal gene transfer

Answer 466

A

new nucleotide base pair
change in amino acid sequence
change to enzyme or cell structure
reduced affinity or activity of antibiotic

Answer 467

A

conjugation, transduction and transformation

Answer 468

A

the transfer of genetic material between bacterial cells by direct cell-cell contact or by a bridge-like connection between two cells; takes place through a pilus

Answer 469

A

genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane
picking up naked DNA

Answer 470

A

process by which foreign DNA is introduced into a bacterial cell by a virus or viral vector

Answer 471

A

MRSA

- VRE

Answer 472

A

Methicillin resistant Staphylococcus Aureus
Staphylococcal casette cromosomi mec (SCCmec) contains resistance gene mecA
gene encodes penicillin-binding protein 2a (PBP2a) that does not bind penicillin i.e. resistance
confers resistance to all B-lactam antibiotics in addition to methicillin

Answer 473

A

Staphylococcal casette cromosomi mec

Answer 474

A

resistance gene mecA

Answer 475

A

penicillin-binding protein 2a (PBP2a) that does not bind penicillin

Answer 476

A

all beta-lactam antibiotics and methicillin

Answer 477

A

Vancomycin-resistant enterococci
plasmid mediated acquisition of gene encoding altered amino acid on peptide chain preventing vancomycin binding
promoted by cephalosporin use

Answer 478

A

cephalosporin use

Answer 479

A

beta-lactamases
ESBL
AmpC beta-lactamase resistance

Answer 480

A

enzymes that hydrolyse penicillins
TEM-1 in E.coli, H. influenzae and N. gonorrhoea
SHV-1 in K. pneumoniae
but such strains typically remain sensitive to beta-lactamase inhibitors

Answer 481

A

extended spectrum beta lactamases

Answer 482

A

• have further mutation at active site means it can destroy more than just penicillin or amoxycillin
• typically they can also inactivate:
- cephalosporins e.g. cefuroxime, cefalexin, cefotaxime
- combination antibiotics such as co-amoxiclav and tazocin

Answer 483

A

• broad spectrum penicillin, cephalosporine and
monobactam resistance
• beta lactamase inhibitor resistant in bacteria such as
Citrobacter spp. and Enterobacter spp.

Answer 484

A

can be treated with quinolones or trimethoprim but may require carbapenam treatment or agents such as fosfomycin or temocillin (use for UTIs and chest infections)

Answer 485

A

treatment

- prophylaxis

Answer 486

A

• specific indications:
- endocarditis
- post-splenectomy
• prevention of post-surgical infection

Answer 487

A

penicillins
cephalosporins
carbapenems
combinations (B lactam inhibitor/B lactam)

Answer 488

A

all beta lactams

Answer 489

A

contraindicated for people who exhibit any type of allergy to penicillins
use with caution if patient has no true IgE mediated/severe allergy

Answer 490

A

streptococci: e.g. S.pneumo and beta-haemolytic streps (A,B,C,G)
also treats some other gram positive bacteria including clostridia (gas gangrene)
IV
narrow spectrum

Answer 491

A

skin and soft tissue infection e.g. endocarditis

Answer 492

A

increasing resistance; enterococci are resistance

Answer 493

A

bacterial pharyngitis - ‘strep throat’
splenectomy prophylaxis
oral

Answer 494

A

has greater activity than benzylpenicillin - broader
H. influenzae
Enterococci
Enterobactericae - E.coli, proteus, shigella

Answer 495

A

pneumonia
skin and soft tissue infection
UTIs

Answer 496

A

safe both orally and IV

- resistance is emerging

Answer 497

A

IV and oral

- S. aureus

Answer 498

A

benzylpenicillin/penicillin G (IV)
phenoxymethylpenicillin/pen V (oral)
amoxicillin (IV and oral)
flucloxacillin (IV and oral)

Answer 499

A

B lactamases are enzymes produced by bacteria that hydrolyse penicillins and thus make them resistant
resemble traditional B-lactam antibiotic e.g. penicillin
they bind to the B-lactamase and protect the antibiotic from degradation

Answer 500

A

clavulanic acid
sulbactam
tazobactam

Answer 501

A

combination of amoxicillin (beta lactam) and clavulanic acid (beta lactamase inhibitor)

Answer 502

A

combination of pipercillin (beta lactam) and tazobactam (beta lactamase inhibitor)

Answer 503

A

for example E.coli exhibits B-lactamase production:

it’s resistant to amoxicillin
but it’s sensitive to amoxicillin and clavulanic acid

Answer 504

A

can be used in those with non-severe penicillin allergies

* can be used to treat meningitis

Answer 505

A

C. difficile and enterococci

Answer 506

A

cefalexin

Answer 507

A

ceftriaxone, cefotaxime (penetrates CNS)

Answer 508

A

earlier generations

Answer 509

A

newer generations

Answer 510

A

aztreonam (IV)

Answer 511

A

only gram negative rods/bacilli

Answer 512

A

safe for those with penicillin allergies
has a lower C.diff risk
can only be used IV
has a narrow spectrum of activity

Answer 513

A

meropenem
ertapenem
imipenem

Answer 514

A

extended spectrum B-lactamases

- AmpC B-lactamases

Answer 515

A

hospital acquired infection (for the sickest and most at risk)

Answer 516

A

• broad spectrum, cover resistant gram negatives
• expensive and have a C.diff risk
• emerging resistance from carbapenemase producing
enterobactericae

Answer 517

A

vancomycin and teicoplanin

Answer 518

A

target the cell wall of bacteria

- gram positive only

Answer 519

A

MRSA and other serious infections

- people with penicillin allergy

Answer 520

A

must monitor nephrotoxicity (for vancomycin more than teicoplanin)
some resistance is possible (Vancomycin Resistant Enterococci (VRE))

Answer 521

A

clarithromycin and erythromycin

Answer 522

A

inhibit protein synthesis
gram positives e.g. S. aureus and atypical pneumonia pathogens as well as group A streptococci
can cover MRSA

Answer 523

A

severe/atypical pneumonia
penicillin allergic patients
MRSA
risk of C. diff as well as resistance

Answer 524

A

clindamycin

Answer 525

A

inhibit protein synthesis

- gram positives e.g. S. aureus and anaerobes and group A streptococci

Answer 526

A

cellulitis (if patient is allergic to penicillin)
necrotising fasciitis
MRSA
has a good oral bioavailability
C. diff risk

Answer 527

A

doxycycline (oral)

Answer 528

A

inhibits protein synthesis

- broad spectrum

Answer 529

A

cellulitis (if patient is allergic to penicillin)
MRSA
possibility of resistance

Answer 530

A

gentamicin (IV)

Answer 531

A

inhibits protein synthesis
broad spectrum
enterobacteriaceae, staphylococci, synergistically to treat streptococci

Answer 532

A

UTIs
infective endocarditis (synergistically)
can be used against extended spectrum B-lactams and AmpC B-lactams
requires monitoring due to the risk of nephrotoxicity

Answer 533

A

linezolid

Answer 534

A

inhibits protein synthesis

- gram positive e.g. MRSA and VRE

Answer 535

A

serious/gram positive infection e.g. skin and soft tissue
good oral bioavailability and penetration
multiple side effects and interactions

Answer 536

A

ciprofloxacin (IV and oral)

Answer 537

A

gram negatives more than gram positives

Answer 538

A

UTIs

- patients with penicillin allergy

Answer 539

A

poor streptococcal activity
good oral bioavailability
can be used against extended spectrum B-lactams and AmpC B-lactams
C.diff risk

Answer 540

A

inhibits nucleic acid

- anaerobic bacteria

Answer 541

A

intra-abdominal infection

Answer 542

A

good oral bioavailability
cheap
emerging resistance

Answer 543

A

folate inhibitor

- broad spectrum

Answer 544

A

can be used against extended spectrum B-lactams and AmpC B-lactams
cheap
however there is increasing resistance

Answer 545

A

e.g. Pseudomonas aeruinosa
hospital acquired infection
has inherent resistance mechanisms

Answer 546

A

pip/tazobactam
ceftazidime
aztreonam (meropenem)
gentamicin
ciprofloxacin (the only oral option)

Answer 547

A

E.coli
Staph saprophticus
Proteus
Klebsiella
Enterococcus

Answer 548

A

trimethoprim for 3 days (if uncomplicated and ‘well’)

Answer 549

A

S.aureus

- Beta-haemolytic streptococci: Group A, C or G streptococci

Answer 550

A

flucloxacillin +/- benzylpenicillin for 10-14 days

Answer 551

A

S.pneumonia

- ‘Atypicals’

Answer 552

A

amoxicillin/co-amoxiclav +/- darithromycin for 5 days

Answer 553

A

varicella zoster virus

Answer 554

A

primary infection with this virus causes chickenpox, which may produce a mild childhood illness, although this can be severe in adults and
immunocompromised patients
type of herpes virus

Answer 555

A

after an incubation period of 14-21 days there is a brief period of fever, headache and malaise
rash is predominantly on the face, scalp and trunk (distribution is like a chickens feathers i.e the beak and legs are relatively untouched)
rash begins as macules and develops into papule and vesicles which heal with crusting
rash will accumulate at warmer areas e.g. shoulders and neck

Answer 556

A

pneumonia - more common in adults than children
pneumonitis - healthy adults have a 15% risk
central nervous system involvement presenting as acute truncal cerebellar ataxia
exhibits viral dormancy in dorsal root or cerebral ganglion which can result in localised reactivation under immunosuppressed conditions - this is shingles (localised)

Answer 557

A

patients are infectious from 2 days before the rash appears since the virus replicates in the nasopharynx and thus can spread in the air

Answer 558

A

due to reactivation of VZV
after the primary infection, herpes zoster remains dormant in the dorsal root ganglia and/or cranial nerve ganglia and reactivation results in shingles
a person with shingles (particularly if the rash is weeping) could cause
chickenpox in a non-immune person after close contact and touch

Answer 559

A

pain (neuropathic) and tingling in a dermatomal distribution precede the rash by a few days
the rash consists of papules and vesicles in the same dermatome
the most common sites are the lower thoracic dermatomes and the opthalmic division of the trigeminal nerve (most common)

Answer 560

A

shingles can be a hallmark of HIV
red flag if multiple dermatomes are involved or peripheral dermatomes
involved - these are unusual signs and need proper investigation for immunocomprimisation i.e. HIV

Answer 561

A

bilateral limb hypoplasia and scarring
seen in 10-15% chickenpox in pregnancy
if maternal chickenpox in first half of pregnancy then 2% risk of foetal varicella syndrome in infants

Answer 562

A

hand foot mouth enterovirus

Answer 563

A

pop lesion and absorb the fluid and then test for chickenpox or enterovirus to find out what it is

Answer 564

A

classic infection that causes lesions on the palms, toes and back

Answer 565

A

rare but severe disseminated infection that generally occurs at sites of skin damage produced by atopic dermatitis, burns, long term use of topical steroids or eczema
dermatological emergency

Answer 566

A

microorganisms capable of causing disease

Answer 567

A

the ability of a pathogen to become established in host, can involve adherence and immune escape

Answer 568

A

the ability of a pathogen to cause disease once established

Answer 569

A

the ability of a pathogen to penetrate mucosal surfaces to reach normally sterile sites

Answer 570

A

microbial factors that cause disease

Answer 571

A

need rapid cell entry
free virus in blood stream is easily neutralised
infected cells are destroyed

Answer 572

A

IgA - Blocks binding
IgM - agglutinates particles and makes it difficult to enter cells
complement - opsonisation and cell lysis
antibodies - neutralise toxins

Answer 573

A

interferon (from T helper or T killer cells) has antiviral action - it induces anti-viral protein DAI (Double stranded RNA activated inhibitor of translation) on nearby cells so they cannot get infected
cytotoxic T lymphocytes kill infected cells (so any virus in cell cannot replicate)

Answer 574

A

double stranded RNA activated inhibitor of translation

- anti-viral protein induced by interferon

Answer 575

A

induces DAI on nearby cells so they cannot get infected

Answer 576

A

cytotoxic T lymphocytes kill infected cells (so any virus in cell cannot replicate)

Answer 577

A

3-4 days post infection the cytotoxic T lymphocyte activity increases
peaks at 7-10 days then declines
cytotoxic T lymphocytes eliminate virus infected cells and so eliminate sources of new viral products

Answer 578

A

influenza virus to respiratory epithelium
varicella zoster virus (chicken pox) to skin cells
yellow fever virus to liver cells
HIV to CD4 T-cells

Answer 579

A

respiratory epithelium

Answer 580

A

skin cells

Answer 581

A

liver cells

Answer 582

A

much of the damage to cells in viral infection is indirect and caused by the innate or adaptive immune response

Answer 583

A

respiratory tract
gastrointestinal tract
skin/mucous membrane break e.g wound

Answer 584

A

number of organisms, virulence and location

Answer 585

A

phagocytes activate

Answer 586

A

immune response

Answer 587

A

antibody response

Answer 588

A

cellular response

Answer 589

A

bacteria compete with host cells and colonising flora
adhesins
biofilms

Answer 590

A

sequestering nutrients
using novel metabolic pathways
out-competing other micro-organisms

Answer 591

A

help bacteria bind to mucosal surfaces

Answer 592

A

• fimbriae and pili filamentous proteins e.g Neisseria
gonorrhoea
• lipid e.g. lipid teichoic acid of Streptococcus pyogenes
• glycosaminoglycans of Chlamydia sp.

Answer 593

A

bacteria can stick together on a surface by secreting an
extracellular polymeric substance of proteins,
polysaccharides and DNA
helps protect against antimicrobials
seen in dental plaque, prosthetic materials and in ottis media (middle ear infection)

Answer 594

A

S.aureus
Streptococcus mutans
Pseudomonas aeruginosa

Answer 595

A

secrete proteases which lyse IgA

Answer 596

A

secretes adhesion molecules

Answer 597

A

has a polysaccharide capsule that prevents phagocytosis

Answer 598

A

releases M protein that inhibits phagocytosis

Answer 599

A

produce coagulase that forms a fibrin coat round the organism thereby protecting it

Answer 600

A

secretes elastase which inhibits C3a and C5a (attracts neutrophils to site of inflammation)

Answer 601

A

escapes from phagolysosome and lives in cytoplasm

Answer 602

A

location of parasite in host

Answer 603

A

humoral immunity

Answer 604

A

cell mediated immunity

Answer 605

A

do not multiple in humans (eggs formed)
not intracellular
few parasites carried
poor immune response

Answer 606

A

snail > larvae > human > liver > intestinal mesentery (bladder veins) > male + female (adult worms) > eggs > faeces/urine > snails

Answer 607

A

IgG and IgE produced
IL5 - eosinophil production
IL3 - mast cell growth
eosinophil basic protein is toxic to worms

Answer 608

A

decreased antigen expression by adult worms
glycolipid/glycoprotein coat is host derived so not perceived as foreign to the immune system - utilises host self antigens

Answer 609

A

monocytes
neutrophils
endothelial cells (IL-1, TNFa)

Answer 610

A

IL-8

* C5a

Answer 611

A

IL-8
C5a
IFN gamma
LPS

Answer 612

A

Prostaglandins

* Leukotrienes

Answer 613

A

Prostaglandins
Leukotrienes
Kinins

Answer 614

A

transplacental transfer
colostrum (in breast milk)
inject preformed antibody
tetanus toxoid
snake venom

Answer 615

A

protective immunity
immunological memory
achieved by: natural infection and vaccine administration

Answer 616

A

inactivated (killed)
attenuated (avirulent)
bacteria or viruses
toxoid vaccines (inactivated toxins)

Answer 617

A

diseases, infections and conditions specifically listed as notifiable under the Public Health (Infectious Diseases) Regulations 1988
it is the legal obligation for any doctor that suspects a case to inform the Proper Office of the Local Authority

Answer 618

A

HIV, bird flu or variant Creutzfeldt-Jakob (vCJD) disease (mad cow disease)

Answer 619

A

acute encephalitis
acute infectious hepatitis
acute meningitis
acute poliomyelitis
anthrax
botulinism
brucellosis
cholera
diphtheria
enteric fever
food poisoning

Answer 620

A

haemolytic uraemic syndrome
infectious bloody diarrhoea
invasive group A streptococcal disease
Legionnaires disease
leprosy
malaria
measles
meningococcal septicaemia
mumps
plague
rabies
rubella

Answer 621

A

SARS
scarlet fever
smallpox
tetanus
TB
typhus
viral haemorrhagic fever
whooping cough
yellow fever

Answer 622

A

anthrax
rabies (no treatment)
cholera
leprosy
malaria

Answer 623

A

acute poliomyelitis (polio)
measles
mumps
rubella

Answer 624

A

acute infectious hepatitis
scarlet fever
tuberculosis

Answer 625

A

detection of any changes in a disease

- allows the development of interventions targeted at vulnerable groups

Answer 626

A

outbreak detection
early warning
forecasting
extent and severity of disease
risk factors

Answer 627

A

investigate to see who might have been exposed to the disease
identify and protect vulnerable persons
exclude high risk persons from high risk setting
educate, inform and raise awareness

Answer 628

A

contact tracing

* partner notification

Answer 629

A

chemoprophylaxis
immunisation
isolation

Answer 630

A

G, A, M, E and D

Answer 631

A

active and passive

Answer 632

A

cell-mediated immunity

* antibody-mediated immunity

Answer 633

A

vaccination stimulates immune response and memory to a specific antigen/infection

Answer 634

A

inactivated (killed) e.g. pertussis and inactivated polio
attenuated live organism e.g. yellow fever, MMR, polio and BCG
secreted products e.g. tetanus & diptheria toxins
the constituents of cell walls/subunits e.g. Hep B
recombinant components - experimental

Answer 635

A

polysaccharide antigens are not as immunogenic as protein antigens (protein vaccine results in a stronger response)
protection is not long-lasting
response in infants and young children often poor

Answer 636

A

must replicate in the vaccinated individual to produce an immune response
takes time (days or weeks) to replicate
usually does not cause disease but some may cause a mild form of the disease
avoid giving live attenuated vaccines to those who are
immunocompromised since they are at risk of infection

Answer 637

A

protection provided from the transfer of antibodies from immune individuals

Answer 638

A

• most commonly it is cross-placental transfer of antibodies from mother to child e.g. measles, pertussis
• or, via transfusion of blood or blood products including
immunoglobulin e.g. Hep B
• passive immunity provided by injection of human immunoglobulin containing antibodies to the target infection

Answer 639

A

protection is temporary - usually only a few weeks or months
temporarily increases person’s antibody level to that specific infection
protection gained within a few days but lasts only a few weeks

Answer 640

A

human normal immunoglobulin (HNIG) derived from the pooled

plasma of donors and contains antibodies to infectious agents that are currently prevalent in the general population

Answer 641

A

used to protect immunocompromised children exposed to measles and of individuals after exposure to hepatitis A

Answer 642

A

person doesn’t develop immunity from vaccine

Answer 643

A

initially responds but the protection wades over time

Answer 644

A

meningitis or septicaemia

Answer 645

A

caused by Neisseria meningitis (gram negative); 10-20% carry this in the back of the throat
seen as gram negative purple diplococci under microscope

Answer 646

A

infection is not easily spread
transmitted person to person by inhaling respiratory secretions from the mouth and throat or by direct contact (kissing)
close prolonged contact usually required
bacteria do not live long outside the body

Answer 647

A

majority of infections occur in children (less than 5)
peak incidence in under 1s
smaller secondary peak in young adults (age 15-19)
less than 5% of cases occur in clusters
most cases are sporadic
outbreaks common among teenagers and young adults e.g. in schools and universities
marked seasonal variation with peak in winter
the winter season coincides with that of influenza

Answer 648

A

distinct serogroups, according to their polysaccharide outer capsule

Answer 649

A

the most common pathogenic serogroups are groups B, C, A, Y and W135
most disease in the UK is caused by serogroups B (59%) and C (36%)
significantly fewer cases caused by serogroup C since routine vaccination introduced

Answer 650

A

brain abscess
brain damage
seizure disorders
hearing impairment
focal neurological disorders
organ failure
gangrene
auto-amputation due to arterial occlusions
death

Answer 651

A

Cefotaxime

- Ceftriaxone

Answer 652

A

case fatality rate around 10%

* more deaths caused by septicaemia than meningitis

Answer 653

A

notification
contact tracing
prophylaxis

Answer 654

A

contact for meningitis is taken to be any person having close contact with a case in the past 7 days
close contact includes:
• kissing
• sleeping with
• spending the night together
• spending in excess of eight hours in the same room

Answer 655

A

warn about symptoms and signs
glass test: petechial spots do not blanch on pressure
contact telephone number

Answer 656

A

for close, usually household contacts
Ciprofloxacin (older children and adults) or Rifampicin (not for pregnant women)
for nasal carriage
reduces spread
does not stop the disease if already incubating it

Answer 657

A

if the serotype of meningococcus is vaccine
preventable, a vaccination may be offered to unprotected contacts
depends on serogroup
but remember neither vaccine efficacy nor coverage is ever 100%
routine childhood immunisations: men B and C

Answer 658

A

sexy students can look bad comemorning

Streptococcus spp.
Staphylococcus spp.
Corynebacterium spp.
Listeria spp.
Bacillus spp.
Clostridium spp.

Answer 659

A

huge vaginas can never provide pleasure

Helicobacter
Vibrio cholera
Coliforms
Neisseria
Parvobacteria
Pseudomonas

Answer 660

A

HAPPH

Herpes viridae
Adenovirus
Parvovridae
Papopviridae
Hepaviridae

Answer 661

A

Clostridium

Answer 662

A

C. perfringens
C. tetani
C. botulinium
C. difficile

Answer 663

A

Cornyebacterium
Listeria
Bacillus

Answer 664

A

C. diptheriae

Answer 665

A

L. monocytogenes

Answer 666

A

B. anthracis

B. cereus

Answer 667

A

Neisseria

Moraxella

Answer 668

A

M. catarrhalis

Answer 669

A

B. fragilis

Answer 670

A

Parvobacteria

- Helicobacter

Answer 671

A

Haemophilus influenzae
Bordatella pertussus
Leigonella pneumonphilia
Brucella
Campylobacter jejuni

Answer 672

A

Eschericia (E. coli)

- Klebsiella (K. pneumoniae)

Answer 673

A

Salmonella
Shigella
Proteus

Answer 674

A

S. typhi
S. paratyphi
S. enterica

Answer 675

A

S. sonnei

- S. dysenteriae

Answer 676

A

P mirabilis

Answer 677

A

glycopeptides

- beta lactams

Answer 678

A

Vancomycin and Teicoplanin

Answer 679

A

severe staph infections e.g. MRSA/C. difficile

- must be monitored to prevent ototoxicity and nephrotoxicity

Answer 680

A

penicillins
cephalosporins
carbapenems

Answer 681

A

benzylpenicillin
flucoxacillin
ampicillin/amoxicillin

Answer 682

A

Strep. infections, pneumococcal pneumonia, meningococcal meningitis, gonococcal infection, syphillis

Answer 683

A

S. aureus, S. pyogenes

Answer 684

A

UTIs, RTIs, listeria, meningitis, entercocci infections, S. pneumonia causing bronchitis

Answer 685

A

S. aureus, streptococci, nisseriae, Haemophilus, coliforms

Answer 686

A

imipenem, ertapenem

Answer 687

A

enterobacteriae, anaerobic bacteria

Answer 688

A

cautions: renal impairment, history of deafness, pregnancy

SEs: nephrotoxicity, ototoxicity, blood disorders

Answer 689

A

CIs: penicllin hypersensitivity

SEs: hypersensitivity reactions

Answer 690

A

CIs: penicillin hypersensitivity

SEs: nausea, vomiting

Answer 691

A

CIs: cephalosporin sensitivity (10% allergic to penicillin will also be ceph sensitive)

SEs: antibiotic associated colitis, Stephens-Johnson syndrome

Answer 692

A

CIs: breast feeding

SEs: increased platelet count (ertapenem), neurotoxicity at very high doses

Answer 693

A

inhibit folate synthesis
inhibit DNA gyrase
binds to RNA polymerase
DNA strand breaks

Answer 694

A

trimethoprim
sulfonamides: sulfamethoxazole
co-trimoxazole: trimethoprim and sulfamethoxazole

Answer 695

A

UTI (not in pregnancy), prostatitis, acute/chronic bronchitis

Answer 696

A

PCP treatment and prophylaxis

Answer 697

A

fluoroquinolones: ciprofloxacin, ofloxacin, levofloxacin

Answer 698

A

Strep. viridans, Strep. pyogenes, Pseudomonas, H. influenza, campylobacter, Chlamydia spp.

Answer 699

A

rifampicin

Answer 700

A

Staph and Strep., mycobacteria (quad. TB treatment)

Answer 701

A

nitroidimazoles: metronidazole

Answer 702

A

anaerobes, parasites e.g. Giardia lambia, prophylaxis in GI surgery

Answer 703

A

CIs: blood dyscrasias

cautions: pregnancy

SEs: hyperkalaemia, depression of haematopoiesis

Answer 704

A

CIs: porphyria

SEs: hyperkalaemia, rash

Answer 705

A

caution: epilepsy, G6PD deficiency, myasthenia gravis

SEs: dyspepsia, sleep disorders, rash pruritus

NB: predispose to MRSA as excreted through the skin and kills commensal organisms

Answer 706

A

CIs: jaundice

SEs: orange discolouration of saliva and urine, anorexia, nausea and vomiting, haemolytic anaemia

Answer 707

A

CIs: interaction with alcohol -> profuse vomiting

SEs: taste disturbance, anorexia

Answer 708

A

chloramphenicol
macrolides
tetracyclines
aminoglycosides

Answer 709

A

H. influenzae meningitis, epiglottitis, Chlamydia, richkettsiae
used widely in the developing world
extended periods of treatment can cause bone marrow depression
neonatal toxicity -> grey baby syndrome

Answer 710

A

Clarithromycin and Erythromycin

Answer 711

A

Strep. pneumoniae, S. aureus, Legionella, Chlamydia, mycoplasma pneumoniae

Answer 712

A

Tetracyclin and Doxycycline

Answer 713

A

broad spectrum

- Strep. pneumonia, Strep. viridans, Strep. pyogenes, S. aureus, Chlamydia, mycoplasma

Answer 714

A

Gentamycin and Streptomycin

Answer 715

A

S. aureus, gram negative bacilli, used for severe sepsis

Answer 716

A

CIs: pregnancy, breast feeding

SEs: blood disorders, optic neuritis, erythema multiforme, grey syndrome (abdominal distension, cyanosis, circulatory collapse)

Answer 717

A

CIs: hepatic impairment (azithromycin)

caution: neonates <2 weeks risk of hypertrophic pyloric stenosis

SEs: rash, arrhythmias, Stephens-Johnson syndrome

Answer 718

A

CIs: children <12 due to deposition in bone and teeth leading to hyperplasia. renal disease

SEs: dysphagia, oesophageal irritation, photosensitivity, headache, visual disturbance

Answer 719

A

CIs: myasthenia gravis

SEs: nephrotoxicity, auditory and vestibular damage. prolonged therapy -> hypomagnesaemia

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