micro sem 1 Flashcards
1
Q
definition of bacteraemia
A
the presence of bacteria in the blood (needs not to be associated with clinical features or any symptoms)
2
Q
definition of septicaemia
A
serious systemic infection associated with bacteria or their products in the blood, resulting in a systemic response and changes in organ perfusion
3
Q
definition of sepsis
A
associated with infection resulting in fever or hypothermia, tachycardia and/or tachypnoea, and high/low WBC count
4
Q
definition of septic shock
A
severe sepsis combined with a potentially fatal drop in blood pressure
5
Q
typical sources of micro-organisms causing septicaemia
A
skin URT genito-urinary tract GI/biliary tract
6
Q
common gram positive bacteria that cause septicaemia
A
staph aureus (golden staph), streptococcus pyrogenes, staph epidermidis, viridans streptococci, strep pneumoniae, enterococcus spp.
7
Q
common gram negative bacteria that cause septicaemia
A
e coli, pseudomonas aeruginosa
8
Q
basis of catalase test
A
if micro-organism has enzyme - able to break down H2O2 to water and oxygen Only aerobic and facultative aerobes have catalase
9
Q
why is the catalase test important
A
if you have found a gram positive bacteria = either staph or strep staph is catalase +ve, while strep is catalase -ve
10
Q
basis of coagulase test
A
a test for the ability of staph sp. to clot plasma by the action of coagulase
11
Q
why is the coagulase test important
A
if staph is found –> do coagulase test –> if positive = staph aureus (makes a fibriogen shield around itself - difficult for IS)
12
Q
why is the lactose test important
A
important to know whether or not a gram -ve bacilli is a lactose fermentor or not
13
Q
what is main reason for doing DIRECT antibiotic susceptibility testing
A
to try and save time (done straight from the blood culture)
14
Q
what is staph aureus resistant to
A
penicillin - always
15
Q
why is cefoxitin susceptibility testing done
A
as a surrogate for methicillin susceptibility testing - cefoxitin a lot easier to use than methicillin - they act in the same way
16
Q
if a wound smells bad…
A
it is probably an anaerobic bacteria
17
Q
clostridium is always
A
- environmental - normal microbiota of the gut - gram +ve rod - strict anaerobe form spores
18
Q
why is strep pyrogenes so pathogenic?
A
- has enzymes that allow it to spread through the tissues - has superantigens –> causes systemic effects - is capsulated by hyaluronic acid - self protein
19
Q
treatment of strep pyrogenes
A
ALWAYS SUSCEPTIBLE FOR PENICILLIN
20
Q
sweet smelling ooze from a wound….
A
probably pseudomonas aeroginosa
21
Q
a patient may be suspected of having a primary immunodeficiency if they have (10)
A
- 8 or more ear infections within one year - 2 or more serious sinus infections within one year - 2 or more months on antibiotics with little effect - 2 or more pneumonias within one year - failure of an infant to gain weight/grow normally - recurren
22
Q
recurrent infections by pyogenic bacteria (E/C bacteria) typically associated with defects in which parts of the immune system?
A
- antibody production - components of the complement cascade - phagocyte function
23
Q
recurrent infection by viruses, I/C bacteria and fungi are typically associated with defects in which part of the immune system? What may this impact on?
A
T cell function may impact on: - function of CD8 cytotoxic T cells - function of CD4 T cells - B cell and macrophage function
24
Q
what micro-organisms is a person susceptible if they have hyper IgM syndrome
A
both extracellular and intracellular pthogens
25
what is the most common reason for Hyper IgM syndrome?
mutation in the gene encoding the CD40 ligand that is induced on activated T cells- required for isotype switching, activating macrophages and generating cytotoxic T cells
26
What does IL-12 receptor deficiency cause
affects the ability of T cells to bind IL-12 and differentiate into TH1 cells resulting in defective IFN gamma production
27
what does an IL-12 receptor deficiency make you susceptible to?
excessof infections with I/C bacteria, such as TB - since macrophages cannot be appropriately activated in the absence of T cell derived IFN gamma
28
deficiencies of antibody production usually results in
difficulties in clearing EC bacteria and usually manifest themselves as recurrent pyogenic infections
29
What does a mutation in the btk gene cause?
pre-B cells cannot differentiate into mature B cells
30
Which parts of the innate immune system can be defective?
- the complement system defect - phagocytic cell defect - cytokine defect
31
what does a deficiency in C3 cause
reduced ability to opsonise organisms for phagocytosis --\> increased susceptibility to pyogenic infections
32
Having a faulty MAC makes you susceptible to infection by which species and why
neisseria genus - able to evade the normal phagocytic defenses so the formation of the MAC is critical for their control
33
What does a LFA-1 deficiency lead to?
the inability of the phagocytes to bind to vascular endothelium and a failure to bind bacteria coated with C3b --\> patients phagocytes fail to migrate to sites of infection, or ingest opsonised organisms --\> overwhelming bacterial infections
34
what is chronic granulomatous disease?
a disease in which phaogcytes ingest but fail to kill ingested organisms
35
what causes chronic granulomatous disease?
patients phagocytes are defective in NADPH oxidase --\> cannot produce superoxide radicals (important for bactericidal pathway)
36
What is IFN-gamma important for?
activation of macrophages to ingest and kill EC pathogens
37
what produces IFN-gamma?
TH1 CD4 cells CD8 T cells NK cells
38
what do you look for in the blood to determine which component of the immune system is defective?
- presence of expected cell populations by flow cytometry - presence of expected levels of complement components - presence of expected antibody isotypes - functional assays - assays for gene defects
39
if a phagocyte can engulf but not kill, what results?
the formation of giant cell granulomas
40
what microorganism normally causes the formation of giant cell granulomas? Why?
mycobacterium - inhibits the killing pathways of activated macrophages, and survive and multiply inside the infected macrophage --\> chronic persistent infection --\> stimulates and is controlled by the development of a granuloma
41
defects in the gene coding for CD40L leads to which typical problems:
- poor B cell activation (poor isotype switching, affinity maturation and memory cell formation) - inefficient induction of cytotoxic T cells - inefficient macrophage activation, resulting in defective cytokine release, and defective respiratory burst
42
what is granuloma development dependent on? (cytokine)
the products of activated T cells - especially IFN-gamma
43
Normal proliferation of T cells is induced by?
IL-2
44
deficiency of LFA-1 leads to...
phagocytes unable to migrate into the tissue
45
a defect in the gene coding for gene rearrangement (RAGs) would lead to..
no T or B cells
46
how do you take blood cultures
take 3 sets of 2 bottles one bottle of the set cultured anaerobically the other aerobically
47
if a wound smells bad, it is probably...
an anaerobic organism associated with dead tissue
48
catalase test is based on
whether or not a bacterium can break down H2O2 to water and oxygen
49
coagulase test is based on the ability to
clot plasma by the action of the enzyme coagulase --\> breaks down fibrin to fibrinogen
50
when do you perform lactose fermentation tests
on gram -ve bacteria
51
colour of gram positive and negative bacteria
positive - purple/blue negative - pink
52
what is the purpose of macconkey agar
it is a selective mediator medium - has lactose as the nutrient: --\> if bacteria ferments lactose = pink --\> if bacteria doesnt ferment lactose = yellow identifies enteric bacterium
53
purpose of oxidase test
mainly for the aerobic and facultatively anaerobic groups of gram negative bacteria (psuedomonas sp are positive)
54
identification of staph aureus
- gram +ve cocci - growth in air - catalase +ve - coagulase +ve
55
identification of psuedomonas
gram -ve rods oxidase \_ve grows aerobically
56
what is the difference in blood pressure when moving your arm around
raised arm = lower BP higher arm = increased BP due to P= pgh
57
difference between primary and secondary ID
primary = inherited, as a result of gene defects, developed in utero secondary = gained over life when something impacts the immune system
58
when does primary ID usually present clinically
6-9 months
59
what does the lack of CD18 cause
(part of integrin molecule on T cells) - T cells cannot get into tissues and therefore build up in the blood
60
what is the classical organism causing consolidation in people with T cell defects
Pneumocystis jiroveci (fungi)
61
lack of CD40L means what
no activation of B cells to help them isotype switch --\> only IgM made against infections - action against viral infection is fine
62
two types of antimicrobial treatment
- empiric therapy - based on the most likely causative organism - directed therapy - based on the results of diagnosis and antimicrobial susceptibility testing
63
which organisms is always susceptible to penicillin
strep pyogenes
64
what am i? Small white colonies with beta haemolysis on HBA Gram positive in chains
Strep A, B or C
65
what are the possible complications of a Strep pyogenes infection
- rheumatic fever --\> rheumatic heart disease - quinsey = peritonsillar abscess - sinusitis - mastoiditis - cellulitis - necrotising fascitis - speticaemia - septic arthris - endocarditis - glomerular nephritis
66
different organisms that cause alpha and beta haemolysis on mcconkey agar
green haemolysis = strep pneumonia beta haemolysis= strep pyogenes
67
what conditions may lower the resistance of the RT to bacterial infections
- viral - smoking - blockage of bronchus - malnourised - COPD - patients undergoing surgery
68
what does the presence of a capsid mean for fighting infection
complement cant bind to it antibodies cant bind to it evades alveolar macrophages
69
what are the features of the secondary immune resonse that we want an ideal vaccine to geerate
- isotype switching - affinity maturation - differentiation into memory cells (all require help from CD4 T cells)
70
how do you activate T cells in a vaccine
- CD40L - cytokines - peptide antigen
71
T independent B cells can only make
IgM antibodies no memory response short lived response
72
how would you look for, and what would you look for when trying to see infection with eukaryotic parasite
- wet prep of faeces - light microscoy - look for parasitic form and cysts
73
if you want to see if you can grow Campylobaccta, which medium do you have to use
Campylobacta agar - has blood and antibiotics it in - needs blood to grow - Ab restricts the growth of anything else
74
which organisms are notifiable to the health department
- Campylobacta - Shigella - Salmonella - EHEC - vibrio cholera - Cryptosporidium
75
which enteric organisms are lactose non-fermenters
Shigella and Salmonella
76
Which organism gives yellow colonies with a black dot in Disoxycholate citrate medium
Salmonella
77
What does salinyte browth do
poisons normal microbiota, but now Salmonella --\> red precipitate "Salmonella test"
78
3 organisms that can cause bloody diarrhoea
EHEC Shigella dysenteriae EAEC that has acquired the Shiga toxin genes
79
What is a CAMP medium used for?
test for Campylobacter
80
What is a disoxycholate citrate plate used for
to test for the presence of Salmonella (will show up as yellow colonies with black dots)
81
how does EHEC cause kidney damage
into blood stream --\> kidney endothelial cell internalises it --\> inhibits protein synthesis --\> cell dies (cytotoxic) --\> inflammatory response --\> fibrin deposition
82
what is the difference between complicated and uncomplicated cystitis
uncomplicated - no underlying medical condions that would predispose them to cystitis complicated - underlying medical conditions
83
what is pain when peeing called
dysuria
84
main causes of cystitis
E coli Staph saprophyticus proteus klebsiella enterococci pseudomonas
85
which organism causing cystitis is associated with sexually active women of reproductive age
staph saprophyticus
86
what is enterococci
gram +ve cocci that is catalase -ve (like strep)
87
how many bacteria are significant in a urine sample
\>10^5
88
how many bacteria are significant in 1 microlitre
100
89
what are the two essential tests on a dipstick that indicates cystitis
leucocyte esterase and nitrites
90
macroscopic look of E coli
large round single colonies that are lactose fermenters
91
macroscopic look of klebsiella
large round single colonies that are lactose fermenters that are shiny due to their polysaccharide capsule
92
why is asymptomatic bacteruremia bad in pregnant women
- predisposes to premature labour - babies tend to be low birth weight for gestation - get increased levels of kidney infection during pregnancy
93
why do you treat urine with an alkali before culturing my M. TB
to get rid of the normal flora (as you have taken a full stream urine so there will be lots of bacteria present)
94
identification of streptococci
- gram positive cocci in chains - pyogenic - no spores - facultative anaerobe - often alpha or beta haemolysis on HBA - catalase negative
95
staph identification
- gram positive cocci in clusters - pyogenic - no spores - facultative anaerobes - catalase positive
96
how would you test to see if you have staph aureus
catalase and coagulase positive
97
how do you get staph
both exogenous (environmental) and endogenous
98
identification of enterococci
- gram positive cocci in pairs or chains - catalase negative - facultative anaerobe (like strep) - non haemolytic
99
identification of pseudomonas
- gram negative bacilli - aerobic, non-spore forming - oxidase positive
100
likely sources of staph aureus
skin, nose, throat, faeces, HC workers
101
likely source of strep pyogenes
nasopharynx, oropharynx
102
likely source of pseudomonas aeroginosa
environmental
103
what is serosanginous discharge
no pus in the discharge
104
what is CD18
common component of integrin molecules needed for adhesion and movement of WBCs into tissues (eg. part of LFA-1)
105
What is strep pyogenes normally associated with
cellulitis necrotising fascitis resp infections endocarditis systemic infections
106
what physical symptoms are characteristic for acute bacterial meningitis
fever stiff neck headache
