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Flashcards in diagnosis of infection Deck (27)
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1
Q

specimen types

A
urine 
swab
blood
tissue
sputum
feaces
2
Q

1)direct detection

A

detection of whole organism by microscopy

detection of component e.g antigen, nucleic acid

3
Q

microscopic

A

CSF in meningitis

gram negative diploccoci = neisseria

4
Q

antigen

A

clostridium difficile glutamata dehydrogenase antigen toxin detected using lateral flow

5
Q

nucleic acid

A

Neisseria meningitidis uses direct sequence specific target

streptoccocus pneumoniae amplify unknown sequence using 16s rRNA match with sequence in database

6
Q

uses of direct detection

A
establishes present of organism at one site
tests for non cultivable organisms
directs empirical therapy 
fast
epidemiological info
7
Q

limitations of direct detection

A

no info on susceptibility testing

8
Q

2) culture

A

isolation of the pathogen allows
identification
typing
susceptibility testing

9
Q

different culture media

A

clostridium perfringens requires anaerobic
mycobacterium obligate aerobe
bordetella pertussis is fastideous - fresh blood and potato starch

10
Q

fresh blood agar

A

non selective

nutricious

11
Q

mannitol salt agar

A

selects for halophile growth and pH indicator for fermenters

12
Q

MacConkey agar

A

bile salts select for enteric organisms
pH indicator detects lactose fermenter - turns red - E. coli
VPAT - selective for neisseria gonorrhea and campylobacter jejuni

13
Q

gram stain

A

gram positive = purple = peptidoglycan

negative = counter stain

14
Q

haemolysins

A

streptococcis
a haemolysins - strep pneumonia (resistant to optochin), strep viridans (oral)
B haemolysis - strep pyogenes

15
Q

oxidase test

A

test for cytochromes
pseudemonas positive = purple
fermenter = no cytochromes = negative = clear = e coli

16
Q

catalase test

A

differentiates streptococci with staphylococci

staph = positive = bubbles

17
Q

coagulase

A

staph aureus is positive

18
Q

biochemical tests

A

AI strips mini biochemical reactions

octal score looked up in a database

19
Q

maldi tof

A

time of flight analysis
mass spectrometer produces spectrum of bacterial proteins
compared to database of known spectra to produce ID

20
Q

culture uses

A

targeted antimicrobial therapy

21
Q

limitations of culture

A

cultivable organisms only

22
Q

succeptibility testing

A

viable organism
measure zone of inhibition
E- test gives MIC
BSAC

23
Q

3) immunological tests

A

detection of an immune response to infection

24
Q

antibody detection

A

ELIZA

IgM permits timing from initial infection

25
Q

seroconversion

A

requires a fourfold rise in antibody titre ie present at both 1/2 and 1/64

26
Q

IFN-y release assay

A

Tuberculosis

27
Q

antibody detection uses and limitations

A

confirms exposure to antigen
epidemiological info
restricted to patients with detectable antigen response - not in immunocomprimised
retrospective - usually too late to treat if immune response high