core microbiology Flashcards
what % of the population carry staph. aureus in their nose?
gram +ve or -ve?
how do they cause more serious infections?
50%
gram positive
adhere to damaged skin
-> produce EXOENZYMES + toxins
- -> these damage tissue
- –> host immune response (inflammation -> pus formation)
what severe effects can infection with staph. aureus have? 6
- bacteraemia/septicaemia
- osteomyeliti/septic arthritis
- endocarditis
- pneumonia
- UTI
- meningitis
what (normal skin) bacterium causes infection in association with ‘foreign bodies’?
(eg intravascular catheters, prosthetic joints, prosthetic cardiac valves etc)
and how does it do this?
staphylococcus epidermidis
most people carry it normally on their skin “EPIDERMidis”
adheres to plastics/metals using GLYCOCALYX (‘slime’), forming biofilms
what is the scientific name of ‘group A strep’ pathogens?
what common problem do these cause?
what less common problems do they cause? 6
streptococcus pyogenes
commonest cause of bacterial sore throat
also causes:
- scarlet fever
- necrotising fasciitis (‘flesh eating bug’)
- other SSTIs
- invasive infections (eg pneumonia)
- puerperal sepsis
- also associated w. secondary immunological presentations (eg glomerulonephritis
what does SSTIs stand for?
skin and soft tissue infections
what bacteria is the commonest cause of bacterial pneumonia and bacterial meningtitis (except in neonates)?
give an example of another common childhood infection it can cause?
streptococcus pneumoniae
can also cause: otitis media
what is otitis media?
middle ear infection
what is the scientific name of ‘group B strep’ pathogens?
what do these commonly cause?
streptococcus agalactiae
commonest cause of BACTERIAL MENINGITIS and SEPSIS in NEONATES (babies aged under 3 months)
“agaLACTiae causes diseases which occur when baby is still drinking MILK”
what bacterium is associated with abscesses?
where does it normally reside?
where do these abscesses most commonly form? 4
streptococcus milleri complex
part of mouth + GI flora
- dental
- lung
- liver
- brain
what is the collective name for a number of species of α-haemolytic streptococci that inhabit the upper respiratory tract ?
give 2 examples of species.
what do these typically cause?
Viridans streptococci
S. oralis
S. mitis
typical cause of SUB-ACUTE BACTERIAL ENDOCARDITIS
- gets in to blood then –> heart valves
nb normally affects people w. underlying heart problems (except in IV drug users and HCAIs)
what is a type of a-haemolytic streptococcus that forms part of bowel flora?
what can it cause?
streptococcus gallolyticus
bacteraemia (septicaemia) with this organism can be associated with colonic malignancies
what are zoonoses?
Zoonoses are infectious diseases of animals (usually vertebrates) that can naturally be transmitted to humans
what bacterium is associated with consuming cheese made from unpasteurised milk and other foodstuffs?
gram +ve or -ve
what does it cause?
listeria monocytogenes
gram positive
rare but significant cause of: - sepsis - meningitis in: - pregnancy - neonates - immunosuppressed patients
where do Corynebacterium species normally inhabit?
is it gram +ve or -ve?
what can it cause?
skin and upper resp. tract
gram positive
causes occasional opportunistic infections associated with devices and trauma
also diptheria!
what is the classic cause of diptheria?
why is it rarely seen in UK now?
Corynebacterium diptheriae
immunisation against it
what bacterium is associated with acne?
gram +ve or -ve?
what can it also cause?
Propionibacterium acnes
gram positive
can also cause:
- device-associated infections
- postprocedural infections
what is a collective term for a number of species of gram NEGATIVE bacilli found in bowel flora?
what are 3 common examples of these?
Enterobacteriaceae (‘coliforms’)
- Escherichia coli
- Klebsiella pneumoniae
- Enterobacter cloacae
what is the most common cause of UTIs?
how does this infection occur?
E. coli
normal bowel flora –> colonise urethral meatus + surrounding area
adhear to uroepithelial cells/urinary catheter materials
–> triggers host inflammatory response
why are UTIs more common in women than men?
shorter urethra in women
shorter distance for bacteria to travel
what’s the difference between staph. and strep. bacteria?
staph = bunches
“STAFF bunch around the water cooler”
strep = lines
“like STEP, which have straight lines”
what bacterium is the coagulase test used to differentiate between?
staphylococcus aureus
(coagulase positive)
Coagulase Negative Staphylococcus (CONS)
what does puerperal mean?
eg puerperal sepsis
relating to or connected with or occurring at the time of childbirth or shortly following, or to the woman who has just given birth.
what disease do you get ‘strawberry tongue’ in?
scarlet fever
“strawberrys are scarlet”
what is sub-acute bacterial endocarditis also known as?
infective carditis
what colour do gram positive/negative bacteria stain?
gram positive = purple
gram negative = pink/red
“red = bad”
what’s the difference between bacteraemia and septicaemia?
Bacteremia is the simple presence of bacteria in the blood while Septicemia is the presence and multiplication of bacteria in the blood.
what is another name for nosocomial infections?
healthcare acquired infections
what is the commonest cause of bacteraemia?
E. coli
what do toxigenic strains of e. coli cause?
severe diarrhoea
if more severe: haemolytic uraemic syndrome - HUS
what is haemolytic uraemic syndrome?
who does it predominately affect?
charachterised by:
- haemolytic anaemia
- acute kidney failure
- thrombocytopenia (low platelets)
children
what is an opportunistic infection?
An opportunistic infection is an infection caused by pathogens (bacteria, viruses, fungi, or protozoa) that take advantage of an opportunity not normally available, such as a host with a weakened immune system, an altered microbiota (such as a disrupted gut flora), or breached integumentary barriers
what is an OPPORTUNISTIC pathogen which often produces green pigment?
gram +ve or -ve?
what type of infections can it cause? 3
pseudomonas aeruginosa
gram NEGATIVE
“pseudo is bad/negative”
- resp infections
- UTIs
- soft tissue infections
- (and others)
nb normally only affects compromised patients
what is a diplococcus cause of meningococcal sepsis and/or meningitis?
gram -ve/+ve?
Neisseria meningitidis
gram NEGATIVE
“meningitis is very bad!”
what is the name of the rash you see in meningitis?
purpuric non-blanching rash
difference between meningitis and meningococcal septsis?
The meningococcal bacteria can affect the body in several ways:
Meningitis is caused when bacteria enter the bloodstream and travel to the meninges, where they multiply and cause inflammation.
Septicaemia is caused when bacteria enter the bloodstream and multiply rapidly. They release toxins that poison the blood.
what organism causes gonnorrhoea?
gram -ve/+ve?
Neisseria gonnorrheae
gram negative
what disease can present in newborns born vaginally to mothers infected with gonorrhea?
opthalmia neonatorum
an infection in baby’s eyes
what bacterium can cause pneumonia, especially in patients with COPD?
gram -ve/+ve?
where is it normally found?
Haemophilus influenzae
gram NEGATIVE
“COPD +/or flu is bad!”
norm resp. tract flora
“COPD patients get FLU jab - nb though flu is a virus! - don’t get confused!!”
what type of H. influenzae organism is more infective/dangerous?
what can this cause?
capsulated types (eg type b) "b for bad"
- meningitis
- epiglottitis
name 4 species of Clostridium and what they cause
are these aerobes or anaerobes?
C. difficile - abx-associated diarrhoea/colitis
C. perfringens - classical cause of gas gangrene
C. tetani - tetanus
C. botulinum - botulism
all ANAEROBES
what’s another name for mycobacterium species?
acid fast bacilli (AFBs)
what is the commonest type of mycobacterium?
what are other types of mycobacterium sometimes called?
Mycobacterium tuberculosis (cause of TB)
atypical mycobacteria
what types of infections do atypical mycobacteria cause?
resp infections in patients w. chronic lung disease
opportunistic infections in immunocompromised patients
“cause infection in ATYPICAL patients”
what are two common types of bacteria without conventional cell walls?
give an example of each and what they cause.
(they don’t stain on gram test)
chlamydia species
- eg C. trachomatis (chlamydia - commonest sti)
mycoplasma species
- eg M. pneumoniae (resp tract infections)
what bacterium causes syphilis?
what shape is it?
Treponema pallidum
“used to get a lot of syphillis in PALaces of middle ages”
spirillum
what other two diseases are caused by spirochaetes (spirillum) bacteria?
leptospirosis
(assosciated w. rat exposure)
lyme disease
(transmitted via tick bites)
if a fungus is keratinophilic, what does this mean?
what type of fungus is keratinophilic?
a fungus which is able to utilise keratin in the skin, hair and nails to grow
dermatophytes
what are the terms when fungi originate from:
a) soil
b) animals
c) other humans
a) geophilic
b) zoophilic
c) anthropophilic
what is the medical and colloquial names for a dermatophyte infection of the skin of the foot?
medical = tinea pedis
colloquial = athletes foot
“PEDis = foot”
what is the medical and colloquial names for a dermatophyte infection of the nails (toe or finger)?
medical = tinea unguium
colloquial = fungal nail disease
“‘ung’ you have yucky nails!”
what is the medical and colloquial names for a dermatophyte infection of the skin of the groin area?
medical = tinea cruris
colloquial = jock itch
“CRuris is in your CRotch”
what is the medical and colloquial names for a dermatophyte infection of the limbs and torso skin generally?
medical = tinea corporis
colloquial = ringworm
“CORPoris is like CORPse, so over your whole body”
what is the medical and colloquial names for a dermatophyte infection of the scalp skin and hair?
medical = tinea capitis
colloquial = scalp ringworm
“capitis is head, like captain”
what is the medical name for a dermatophyte infection of the skin of the face (shaved)?
medical = tinea barbae
“BARBae is like BARBer”
is athlete’s foot more common in men or women?
men
what age group is fungal nail infection most common in?
the elderly
how does athletes foot present?
itchy, flaky fissuring of skin
(especially inbetween toes or on soles of feet)
very little, if any, redness or inflammation (arouse very little immune response)
may spread to infect toe nails or may have secondary bacterial infection
what is it called when the whole of the skin of the foot is affected by athletes foot?
moccasin foot
what are the 3 main genera of dermatophytes?
Trichophyton
Microsporum
Epidermophyton
what is onychomyosis?
what 3 changes are seen?
fungal infection of the nail (tinea unguium)
thickening, discolouring + dystrophy of the nail
what are the 4 main types of fungal infection of the nail?
aka onychomyosis/ tinea unguium
1) lateral/distal subungual (underneath toe nail)
2) superficial white (usually get if immunocompromised)
3) proximal (hardest to treat)
4) total nail dystrophy (if others are untreated)
how does tinea cruris typically present?
aka jock itch
itching, scaling, erythematous plaques w. distinct edges
(may extend to butt, back + lower abdo)
nb more common in men
why might a plaque of tinea cruris have blurred (instead of distinct) edges?
if it is misdiagnosed and treated with topical steroids
how does tinea capitis normally present?
range from slight inflammation, scaly patches, with alopecia, ‘black dots’, ‘gray patches’ to severe inflammation
what is kerion celsi?
a more serious type of tinea capitis, usually from zoophilic dermatophytes
get boggy, inflammed lesions on scalp
can lead to hair loss and scarring
what is favus?
a rare type of tinea capitis
presence of cup shape crusts or scutula on the scalp
what are the three types of hair invasion seen in tinea capitis?
- endothrix = spores inside hair shaft (lead to black dots)
- extothrix = spores outside hair shaft
- favic = hyphae only in hair shafts (occurs in favus)
what is the typical presentation of tinea corporis?
aka ringworm
circular, single or multiple erythematous plaques
(may extend from eg scalp or groin)
what is formed when tinea corporis invades a follicle?
majocci’s granuloma
how do you treat tinea capitis?
with systemic (oral) antifungals
topical treatment will NOT be curative (it only reduces spread)
nb topical antifungals can be used for other types of dermatophyte infection
what genus of fungus causes oral and vaginal thrush?
which species is the most common?
candida
candida albicans
“ALBIcans, like albino, you get white plaques with thrush”
what are the 4 types of superficial candida infection of the oral mucosa?
- acute pseudo-membranous
- chronic atrophic
- angular cheilitis
- chronic hypoplastic
what three types of people tend to get acute pseudo-membranous (a type of superficial candida infection of the oral mucosa)?
what does this infection look like?
- low CD4 count (<200 cells/ui) - immunocompromised
- younger patients
- asthma with steroid inhalers
yellow/white plaques in oral cavity that can be ‘brushed off’
what type of person tends to get chronic atrophic oral candida infection?
what does the infection look like?
older people
erythema
- get a very red, swollen, bumpy tongue
what is angular cheilitis?
a type of superficial candida infection of the oral mucosa
- candida PLUS STAPHYLOCOCCUS
get red swollen patches at normally corners of mouth
what is chronic hypoplastic candida?
aka oral leukoplakia
get white plaques which CAN’T be scratched oof
- considered to be premalignant
so may undergo malignant transformation
in general, what 4 types of patients tend to be more at risk of getting candida infections?
- HIV/AIDS patients (even on retroviral therapy)
- on antibiotics (lowers competition for fungi)
- head + neck cancer (radio + chemo affect immune response + salivary secretions)
- in patients generally (increases colonisation + likely to be at least slightly immunocompromised)
what % of women will be affected by candida vulvovaginitis at least once during childbearing years?
what is this also known as?
70-80%
thrush
nb infections are often worse if they occur during pregnancy
what are the 3 commonest symptoms of candida vulvovaginitis?
- pruritis (itching)
- burning sensation
(- discharge)
what is the normal treatment for superficial candidosis?
when should this NOT be given? what is given instead?
oral azoles (esp fluconazole)
“thrush is an AZ OLE!”
during pregnancy!! (azoles increase risk of teratologies)
- TOPICAL azoles can be used instead
what is Candida
endopthalmitis?
candida infection of the intraoccular cavities
what organs can be affected by systemic candida infections?
where is said infection normally acquired from?
who is most likely to get a systemic infection?
almost any organ
acquired from:
- colonised skin
- colonised mucosal sites
- GI tract
immunocompromised patients
candida oesophagitis:
- who is most likely to get it?
- what are the symptoms?
- how is it diagnosed?
HIV patients
pain/difficulty on swallowing/eating
diagnosed by endoscopy with biopsy
candida endocarditis:
- what’s it caused by?
- who is most likely to get it? 2
- how is it diagnosed?
- how is it treated?
cause: rare consequence of candidaemia
- IV drug users
- heart valve surgery patients
vegetations seen on heart valves on ultrasound
difficult to treat without valve replacement
what are the symptoms of candida endocarditis? 4
- fever
- weight loss
- fatigue
- heart murmur
renal candidosis:
- how does infection get to kidney?
- who is most likely to get it? 2
- what are the symptoms? 3
candidaemia
- candida from blood lodges in kidney tissue during filtration of blood
- immunocompromised
- premature neonates
- fever
- abdo pain
- oliguria (very little urine produced) OR anuria (no urine produced)
urinary tract candida infection:
- who is most likely to get it? 3
- why is it hard to diagnose?
- why is it hard to manage?
- women
- diabetics
- people with damaged/abnormal urinary tracts
hard to diagnose:
- candiduria (candida in urine) is common, may or may not indicate infection
hard to manage:
- because few antifungals are secreted in urine
candida peritonitis:
- who is most likely to get it? 2
- what are the symptoms? 4
- how is a diagnosis made?
- how is it treated?
- patients on peritoneal dialysis
- perforation of bowel during surgery
symptoms:
- fever
- abdo pain
- nausea
- vomitting
diagnosis: culture from peritoneal fluid
treatment: source control/drainage AND antifungals
hepatosplenic candidosis:
- who is most likely to get it?
- what is the natural history of the disease?
- what are the symptoms/signs?
leukamia (or other haematological malignancy) patients - almost always!
candidaemia during periods of neutopenia (low neutrophils)
- > during neutrophil recovery, yeasts lodge in liver + spleen
- > abscess formation (bulls eye sign)
symptoms/signs:
- abscess formation (bulls eye) (seen on scans)
- fever
- liver function disturbance
nb antifungal therapy may be ineffective as dead fungus continues to trigger inappropriate inflammatory response
if you find candidaemia in a patient, what 3 things should you do?
- remove lines (where possible)
- start antifungal treatment
- check heart and eyes
what is the most common disease-causing aspergillus species? (95% of cases)
Aspergillus fumigatus
“you contract aspergillus via the FUMES, ie via inhalation”
what are the 4 types of aspegillosis?
who gets each type
(ie reaction to inhaling aspergillus)
1) space occupying/non-invasive (aspergilloma, ‘fungal ball’)
- if you already have a lung cavity
2) allergic reaction (allergic bronchopulmonary aspergillosis, allergic sinus disease)
- asthma
- cystic fibrosis
3) chronic infection (chronic pulmonary aspergillosis)
- if you have chronic lung disease
4) invasive infection (invasive pulmonary aspergillosis, invasive aspergillus sinusitis)
- immunocompromised
- leukaemia
name 3 reasons why people may have lung cavities where aspergillomas may then form.
are aspergillomas dangerous?
- previous TB
- previous sarcoidosis
- previous surgery
normally not dangerous
- BUT may break up, causing haemoptysis + are potentially fatal
nb aspergillomas are hard to treat
allergic aspergillosis:
- what are the symptoms? 2
- why does it occur?
- what is the treatment? 2
symptoms:
- wheezing
- breathlessness
why:
- IgE reaction to aspergillus
treatment:
- antifungals
- steroids
chronic pulmonary aspergillosis (CPA):
- which patients is it most common in?
- symptoms? 4
- signs? 2
COPD patients
symptoms:
- cough
- wheezing
- breathlessness
- chest pain
signs:
- consolidation on CT
- cavities on CT
nb here the aspergillus CAUSES cavity formation, in aspergillomas the fungus just occupys cavities which are already there
invasive aspergillosis:
- which patients are most likely to get this? 3
- what is the natural history of this disease?
- what do you see on CT scans?
- what is the prognosis?
- haem malignancies
- stem cell transplant
- solid organ transplant
natural history:
- low neutrophil counts
- > angioinvasion of lung tissue
- -> dissemination in 25% of cases to extrapulmonary sites
on CT:
- halo and air crescent signs
moderate to poor prognosis (even with aggressive anti-fungal treatment)
when diagnosing aspergillosis, what are serology tests looking for?
in immunocompetent patients
= antibody detection
in immunocompromised patients
= antigen detection
what is the treatment for aspergillomas?
surgical resection
what is the term for when there is an association between two organisms in which both species benefit from the interaction?
mutualism
what is the term for when a parasite derives benefit and the host gets nothing in return but always suffers some sort of injury?
parasitism
what is the term for when only the parasite is deriving benefit, WITHOUT causing injury to the host?
commensalism
what is a definitive host?
either:
- harbours the adult stage of the parasite
or:
- where the parasite utilises the sexual method of reproduction
nb all parasite lifecycles begin with the definitive host
what is an intermediate host?
harbours the larval or asexual stage of the parasite
nb some parasites require 2 intermediate hosts to complete lifecycle
what is the term for a type of parasite host where the parasite remains viable but without further development?
paratenic host
what are the 2 different groups of helminths (macro-parasites)? (scientific + common names)
Platyhelminths (flat worms)
nematodes (round worms)
what are the definitions of:
- direct life cycle?
- indirect life cycle?
- complex indirect lifecycle?
direct:
- only one host (the definitive host)
indirect:
- 2 hosts (definitive + intermediate)
complex indirect:
- more than 2 hosts (possibly incl paratenic host)
what is the scientific name for the most common intestinal nematode?
what type of lifecycle does it have?
what is the path of the parasite once in the body?
ascaris lumbricoides
direct (we are the only hosts)
- inhaled into lungs
- breathed out into mouth
- swallowed into GI tract
what is loefflers syndrome?
what are the symptoms? 5
Loeffler’s syndrome is a disease in which eosinophils accumulate in the lung in response to a parasitic infection (normally ascaris)
- dry cough
- dyspnoea
- wheeze
- haemoptysis
- eosinophilic pneumonitis
what are the symptoms of the ‘intestinal phase’ of ascariasis? 5
aka infection with round worm
- malnutrition
- malabsorption
- migration (into hepatobiliary tree)
- intestinal obstruction
- worm burden
what is the treatment for ascariasis?
aka infection with round worm
albendazole
prevents glucose absorption by worm, it starves, detaches and is passed out of anus
what is the scientific term for a fluke worm?
what disease does it cause?
what type of parasite is it?
schistosoma
billharzia
trematode (a type of platyhelminth, ie flat worm)
what is bilharzia also known as?
what can it cause, if untreated?
what are the intermediate hosts?
schistosomiasis
- bladder cancer
- liver cirrhosis
freshwater snails
where do people catch billharzia from?
any water where infected person has urinated or excreted (also presence of snails)
what is the clinical timeline of schistosomiasis?
swimmers itch
- an immune reaction, lasts about a week
katayama fever
- immune reaction to haematogenous spread, after about a fortnight
- general malaise
- fever
- stomach cramps
chronic schistosomiasis
- symptoms depend on blood vessels which worms inhabit
what are the symptoms and features of chronic schistosomiasis in the urinary system? 3
- haematuria
- bladder fibrosis + dysfunction
- squamous cell cancer of bladder
what are the symptoms and features of chronic schistosomiasis in the liver/GI system?
- portal hypertension
- liver cirrhosis
- abdo pain
- hepatosplenomegaly
what is the treatment for schistosomiasis?
praziquantel
***way to remember?
nb very easy treatment but provides no immunity to future infections
hydatid disease:
- what is definitive host?
- how do humans get it?
- what does it cause in the body?
- how is it diagnosed?
- what is the treatment?
- how do you prevent spread?
definitive host: dogs
exposure is via eating things which are contaminated with dog faeces
in body:
- cysts (70% liver, 20% lungs)
- can remain asymptomatic for years
- symptoms arise from:
- —-mass effect
- —-secondary bacterial infection
- —-cyst rupture hypersensitivity
diagnosis:
- imaging
- serology
treatment: surgically remove cyst
control:
- regularly deworm dogs
- hand hygiene
- safe disposal of animal carcasses
what are the 4 species of plasmodium which cause malaria?
P. falciparum (most common)
P. vivax
P. ovale
P. malariae
what are the symptoms of malaria? 7
why do these symptoms occur?
- fever + rigors
- cerebral malaria (confusion, headache, coma)
- renal failure (black water fever)
- hypoglycaemia
- pulmonary oedema
- circulatory collapse
- anaemia, bleeding + DIC
parasites rupture RBCs, block capillaries + cause inflammatory reaction
nb returning traveller + fever = malaria!! (until proven otherwise)
what tests are used to diagnose malaria? 3
- thick + thin microscopy (most commonly used)
- serology (detection of antigen in blood)
- PCR - detection of malarial DNA
what is the treatment of malaria?
very complicated (specialists deal with it!)
basically some sort of QUINE derivative (suffix of drug)
AND supportive therapy
- management of seizures, pulmonary oedema, acute renal failure + lactic acidosis
- exchange transfusion may be helpful in hyperparasitaemia
what is cryptosporidiosis?
cause?
spread?
diarrhoeal disease caused by cryptosporidium parvum + homins (microparasites)
human -> human spread or animal -> human spread
faecal oral spread
what are the symptoms of cryptosporidiosis?
- watery diarrhoea with mucus (no blood)
- bloating
- cramps
- fever
- nausea
- vomiting
who is at risk of cryptosporidiosis? 9
human-human spread:
- regular users of swimming pools (can be chlorine resistant)
- childcare workers + parents
- nursing home residents/carers
- healthcare workers
- travellers
animal-human spread:
- backpackers, campers, hikers
- farm workers
- visitors to farms/petting zoos
- consumers of infected dairy products
how do you diagnose cryptosporidosis? 2
faeces sample
- acid fast staining
- antigen detection by EIA
what is treatment for cryptosporidosis?
symptomatic:
- rehydration etc
- nitazoxanide
for immunocompromised, young + old:
- paramomycin (to kill parasite)
- nitazoxanide (effectiveness is unclear
- octreotide (reduce cramps + frequency)
- HIV patients, HAART should be quickly initiated
what is a sexually transmitted parasite?
what disease does it cause?
what are the symptoms? 4
trichomonas vaginalis
trichomoniasis
men = asymptomatic
women:
- smelly vaginal discharge
- dyspareunia (painful sex)
- dysuria + lower abdo discomfort
- punctuate haemorrhages on cervix (‘strawberry cervix’)
how is trichomoniasis diagnosed?
how is it treated?
- identification of organism in genital specimens
- metronidazole
treat partner simultaneously
what is giardiasis?
what does it cause?
how is it spread?
flagellated protozoan
asymptomatic –> severe diarrhoes + malabsorption
(can cause chronic disease)
faecal-oral spread
what are the symptoms of giardiasis? 5
how long do they last?
- diarrhoea
- abdo pain
- bloating
- nausea
- vomitting
1-3 weeks
what is the drug suffix used for anti-fungal drugs?
-azole
how is giardiasis diagnosed?
how treated?
how prevented?
- identification of cysts or trophozoites in faeces
- metronidazole/tinidazole (antifungal drugs)
- hygiene measures
- boiling water
what % of diagnoses depend on laboratory tests?
70%
what is renal 1 blood test?
a special set for renal, basically a more indepth version of U+Es
what is CRP blood test?
C-reactive protein
- a non-specific marker for inflammation
what is the correct term for a ‘normal range’? what is the definition of this?
reference range:
defines the values of a biochemical test found in healthy subjects against which patient values can be compared
normally taken as two SD from the mean
- so 5% of results which are outside normal range, are still physiologically ‘normal’ (false positive)
artificial concept, cut-offs are arbitrary!
what’s the difference between specificity and sensitivity?
test sensitivity is the ability of a test to correctly identify those with the disease (true positive rate)
whereas test specificity is the ability of the test to correctly identify those without the disease (true negative rate).
what are 3 strategies which can be used to improve quality of tests?
- select a more appropriate ‘normal’ population
- use a combination of tests (eg LFT profiles)
- combine tests to achieve a diagnostic goal, eg neonatal screening for PKU and hypothyroidism
(very sensitive first line test, low cost - ensures no false negatives –> specific test for 1st screen positives, higher cost - rules out false positives)
what 9 diseases are tested for in neonatal screening (via the heel prick test)?
- sickle cell disease
- cystic fibrosis
- congenital hypothyroidism
- phenylketonuria (PKU)
- medium-chain acyl-CoA dehydrogenase deficiency (MCADD)
- maple syrup urine disease (MSUD)
- isovaleric acidaemia (IVA)
- glutaric aciduria type 1 (GA1)
- homocystinuria (pyridoxine unresponsive) (HCU)
what factors can affect reference range?
- age
- gender
- diet
- pregnancy
- time of month (menstural)
- time of day
- time of year
- weight
- stimulus (eg insulin, white coat hypertension)
what 2 substances in blood tests vary according to the time of year?
- vit d
- calcium
what substance in blood tests vary according to the time of day?
cortisol
very important to know what time of day cortisol test is taken! (best time is midnight or 9am)
name 4 common drugs that have narrow therapeutic indexes
- digoxin
- lithium
- warfarin
- phenytoin (epilepsy drug)
what is the treatment for paracetamol overdose?
Activated charcoal can be used to decrease absorption of paracetamol (if the person presents for treatment soon after the overdose)
antidote = acetylcysteine
(acts as a precursor for glutathione, helping the body regenerate enough to prevent damage to the liver)
16 year old boy presents to hospital in deep coma.
On examination he is severely dehydrated and has deep sighing respiration.
What are the two most likely diagnoses?
what tests would you do? 4
why?
diabetic ketoacidosis (due to type 1 diabetes)
Salicylate OD (overdose of aspirin, ie salicylic acid)
- glucose
- blood gases (test for acidosis, would expect low pH)
- U+E (would expect low sodium, due to polyuria, high potassium, due to acidosis, would also expect high levels of blood ketones)
- salicylate
what are the symptoms of (untreated) type 1 diabetes? 3
- weight loss
- polyuria
- thirst
what acute complication can occur in type 1 diabetes?
how might this present?
why might this exacerbate the symptoms of diabetic ketoacidosis?
systemic infection (due to high blood sugar)
rigor (violent shivering) is a sign of septicaemia
infection shoots his cortisol up (cortisol counterbalances insulin, bit like glucagon) and so the rise in cortisol (due to the infection) exacerbates the problem of diabetes and increases the breakdown of fat into ketones (lower ph further)
why does blood potassium increase in diabetic ketoacidosis?
how should you manage this?
high blood H+ concentration pushes intracellular K out of the cells and into the blood (where a lot of it gets peed out dt polyuria) but a lot still stays into the blood.
So paradoxically the patient is deficient in K even though his BLOOD K is higher than the reference range (because his intracellular K is so low)
when you treat his acidosis: all that blood K will go into the cells and he will become hypokalemic (ie low BLOOD K level) which can easily cause heart arrythmias + death!
– so monitor K very closely and give him K as you’re treating the acidosis (and diabetes)
what does HbA1c measure?
HbA1c is stable glycosylated haemoglobin
Its percentage concentration indicates cumulative glucose exposure
what are the 4 components of viruses?
which 2 of these do are viruses have?
1) genome (RNA or DNA)
2) capsid (protein coat)
3) envelope (lipid bilayer)
4) enzymes (eg reverse transcriptase)
ALL viruses have 1+2
what type of viruses are herpes viruses?
give 5 common types of human herpes virus?
what are herpes viruses characterised by?
double-stranded enveloped DNA viruses
- herpes simplex 1
- herpes simplex 2
- varicella zoster
- epstein barr
- cytomegalovirus
ability to establish latency (after primary infection) + reactivate later in life
what are the common disease names for herpes simplex 1 + 2?
what % of people will experience them in their lives?
HSV-1 = cold sores
(80% will get)
HSV-2 = genital herpes
(10-20% will get)
what are 3 serious syndromes which are complications of herpes simplex virus?
which strain normally causes each?
1) encephalitis (95% caused by HSV-1)
- often severe or fatal (fever, headache, reduced GCS)
2) meningitis (norm HSV-2)
- often follows genital lesions
3) neonatal herpes (almost always HSV-2)
- severe disseminated viraemia (dt vertical transmission during vaginal birth)
what is the common name for varicella zoster virus?
epidemiology?
mode of transmission?
chicken pox (or shingles/herpes zoster if reactivation)
95% of people in west
(drops to 50% if grew up close to equator, so check with people who grew up abroad)
transmission:
- resp droplet from person w PRIMARY infection
- vesicle fluid from person w primary infection OR reactivation
nb latency is established in DORSAL ROOT GANGLION
- so shingles is found in a particular dermatome
what are 3 rare complications associated with primary infection of varicella zoster virus?
aka chicken pox
- pneumonitis (esp adults) (inflammation of alveoli)
- encephalitis
- acute cerebellar ataxia (inflammation of cerebellar)
what is the common name for the epstein barr virus (EBV)?
what % of UK pop will get it?
mode of transmission?
glandular fever
95% (50% by age 5)
- saliva (‘kissing disease’)
- genital secretions
what is infectious mononucleosis?
symptoms? 5
aka glandular fever (or ‘mono’)
infection by:
- epstein barr virus (90% cases)
- cytomegalovirus (10% of cases)
- sore throat
- fever
- lymphadenopathy (swollen lymph nodes)
- hepatosplenomegaly
- fatigue
nb on blood film: atypical lymphocytes (which look like monocytes, hence name: mononucleosis)
nb reactivation if unwell or immunosuppressed
cytomegalovirus:
- prevalence?
- mode of transmission?
in UK, prevalence = age (roughly)
- ie 20% of 20 yr olds have had it
- 50% of 50 year olds have had it
- etc
- saliva
- genital secretions
- infected donated blood or organs
what 4 clinical syndrome can present with an infection of cytomegalovirus?
- infectious mononucleosis
- congenital infection (CMV is a teratogen)
- immunosuppressed transplant recipients (solid organ or bone marrow)
- – either primary infection from new organ/blood products
- – or reactivation as a result of immunosuppression
- patients with advanced HIV/AIDS
- – reactivation of latent CMV
what birth defects can a baby born to a mother with a primary infection of cytomegalovirus (CMV) have? 4
- retinitis
- deafness
- microcephaly
- hepatosplenomegaly
what can reactivation of latent cytomegalovirus in advanced HIV/AIDS patients present as? 2
- retinitis
- colitis
what % of ‘common colds’ are caused by rhinoviruses?
symptoms? 6
30-50%
- sneezing
- nasal obstruction + discharge
- sore throat
- cough
- headache
- fever
what are the 3 distinct types of influenza?
- influenza A
- influenza B
- influenza C
nb influenza A mutates regularly, strains vary yearly (yearly flu vaccine)
- B + C are relatively stable
what are the symptoms of flu? 6
what is a more serious complication of flu?
- FEVER
- MYALGIA (muscle aches)
- headache
- cough
- sore throat
- nasal discharge
post-influenza secondary bacterial lung infection
- higher mortality than actua flu
respiratory synctial virus:
- who gets it?
- what does it cause?
- symptoms? 4
- very common amongst young children (esp in 1st year of life, + in winter)
- bronchiolitis (inflammations of bronchioles, smallest airways)
symptoms:
- cough
- wheeze
- hypoxia
- fever
kids can deteriorate very fast
what is the clinical course of HIV infection?
HIV –> T helper (CD4) cells
2-6 weeks after transmission: patients MAY develop an acute seroconversion illness (fever, sore throat, lymphadenopathy)
next 5-15 years: asymptomatic chronic infection
AIDS: increase in viral load, fall in CD4 cells, patients vulnerable to opportunistic infections
what is an AIDS defining illness?
name 5 common ones.
an illness which, if someone with HIV gets, defines them as having AIDS (occording to WHO)
- tuberculosis
- pneumocystis pneumonia
- cryptococcal meningitis
- cerebral toxoplasmosis
- kaposi’s sarcoma
what are the 5 types of hepatitis?
how are each of them spread?
faeco-oral spread
- Hep A
- Hep E
blood bourne spread
- Hep B (Hep D - defective virus, can only survive w hep B)
- Hep C
Hep A:
- epidemiology?
- symptoms? 6
- who does it affect?
epidemiology:
- endemic in developing world
symptoms: - nausea - myalgia - arthralgia - fever - jaundice - right upper quadrant pain (self-limiting condition)
predominately infects children (90% are asymptomatic) but if adults get it then 50% have symptoms
associated with:
- lower socioeconomic groups
- returning travellers
- MSM
“Adults are more seriously affected by hep A”
“A = Acute”
Hep E:
- epidemiology?
- symptoms? 6
- who does if affect?
epidemiology:
- genotypes 1 + 2
- – endemic in asia and africa (associated w contaminated water)
- genotype 3
- – clusters of cases in west europe + north america (associated with pigs, undercooked meat)
symptoms: - nausea - myalgia - arthralgia - fever - jaundice - right upper quadrant pain (self-limiting)
vast majority are asymptomatic! (95%)
- peak incidence in young adults (15-35 yrs)
- high mortality (25%) in pregnant women
- more severe in older males
- more severe in people w chronic liver disease
“E = Pigs, Pork + Pregnant women”
Hep B:
- mode of transition?
- clinical course?
predominately vertical (can spread sexually as well)
clinical course:
- post transmission: acute clinical hepatitis MAY occur (90% kids + 50% adults are asymptomatic of acute infection)
- Hep B is either cleared or -> chronic
nb risk of -> chronic is inversely proportional to age at transmission (ie kids have high change of becoming chronic, adults have lower chance)
over time:
chronic hepatitis -> cirrhosis -> hepatocellular carcinoma
“B - Babies almost always get it from mothers”
Hep C:
- mode of transmission?
- who tends to get it?
- clinical course?
transmission: - IVDU - needlestick injuries - contaminated blood transfusion (- vertical + sexual transmission is lees common)
who gets it:
- 50% of IVDU have it!!
clinical course:
- post transmission: 25% are symptomatic
- 15% clear virus
- 85% become chronically infected (age at infection is irrelevant)
over time:
- chronic hepatitis -> cirrhosis -> hepatocellular carcinoma
Norovirus:
- who gets it?
- mode of transmission?
- symptoms? 1
who gets it:
- common, 90% of adults have had it at some point
- immunity is short-lived (<1 year), so often get it again
- associated with POINT-SOURCE OUTBREAKS (eg cruiseships, hospital wards, military)
transmission:
- ingestion/inhalation of vomit particles! (nom!)
symptom:
- a lot of vomit!
Rotavirus:
- who gets it?
- mode of transmission?
- symptoms? 3
who gets it:
- CHILDREN (80-100% infected in 1st 3 years of life)
- reinfections can occur but 1st is most severe
- seasonal, peaks in winter
- major cause of infant mortality in developing world
mode of transmission:
- faeco-oral, via:
- – contaminated food or water
- – aerosolised vomit
symptoms:
- fever
- vomiting
- watery diarrhoea
nb called rota virus as it is circular
name 5 common enteroviruses.
- polio
- coxsackie A
- coxsackie B
- enterovirus
- echoviruses
what is the mode of transmission and pathogenesis of enteroviruses?
faeco/oral, contaminated food/water
replicate in gut, but do NOT cause GI symptoms
from gut -> lymph nodes -> viraemia -> symptoms
what clinical syndromes are common to al enteroviruses?
- fever-rash syndromes in children, incl hand,foot + mouth (DIFFERENT to foot and mouth!!)
- ‘common cold’
- meningitis (50% of viral meningitis are enteroviruses, though these are often milder than from other causes)
- encephalitis
- severe disseminated disease in neonates
what specific clinical syndrome is associated with coxackie A virus?
Herpangina
small mouth blisters on back of throat
what specific clinical syndrome is associated with coxackie B virus?
pericarditis
inflammation of pericardium around heart
parvovirus:
- common disease name?
- scientific disease name?
- mode of transmission?
- symptoms?
‘slapped cheek syndrome’
erythema infectiosum
- droplet transmission from respiratory route
infects ertythrocyte progenitor cells - causing transient anaemia!
symptoms:
- fever
- coryza (inflammation of mucosa in nose)
- fiery red rash to cheeks
what are two complications of parvovirus infection? who do they occur in?
transient aplastic crisis:
- affects those w high RBC turnover (eg sickle cell, thalassemia) as unable to cope with transient anaemia
- dyspnoea
- confusion
- cardiac failure
infection during pregnancy:
- 7-10% foetal loss if maternal parvovirus in first 20 wks
- 2-3% develop HYDROPS FETALIS (= severe foetal anaemia -> oedema, ascites, heart failure)
- – treated with interuterine blood transfusion
human prion diseases:
- where disease norm confined to?
- name of histological change?
- incubation times?
- prognosis?
norm confined to CNS
produce SPONGIFORM change in brain histology
long incubation times (up to 30 years)
progressive + fatal
what are the two different types of Creutzfeld-jakob disease?
what are they caused by?
what are the symptoms? 3
sporadic (sCJD)
- increadibly rare point gene mutation (1 in a million)
new variant (nvCJD) - consumption of beef infected with BSE (bovine spongiform encephalopathy)
symptoms:
- progressive ataxia
- depression
- dementia, then death
