Review of Microbiology Flashcards

1
Q

usual bacteria at various body sites

A

throat: Staphylococci, S.pneumoniae, H.influenzae, Candida

Paranasal sinuses: S.pneumoniae, H.influenzae

Skin flora:
S.aureus, S.pyogenes, Candida

Mouth and teeth

  • staphylococci
  • candida

Upper bowel:

  • E coli
  • enterobacteriacae
  • enterococci
  • yeast

Lower bowel:

  • same as upper bowel +
  • bacteroides

Perineum and urethra

  • same as skin and lower bowel +
  • mycoplasma

Adult vaginal flora

  • yeast
  • actinomycetes
  • mycoplasma
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2
Q

methods used for identification of bacteria

A

(1) Microscopy - Gram staining and shape (bacilli/cocci) under microscope
(2) Culture (broth or agar)

(3) biochemistry test: specific nutrients and enzymes
- fermenters vs non-fermenters
- catalase, coagulase, oxidase

(4) serologic/immunologic diagnostics: detect antigen or ab
(4) Molecular/nucleic acid-based diagnostics (PCR)
(5) Mass spectrometry (MALDI-TOF)

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3
Q

AST: MIC test; what is done in this method

A
  1. Agar or broth dilution method:
    - agar with diff conc of abx
    - MIC is the lowest conc of an antimicrobial that prevents visible growth of an organism

(2) Disk diffusion method
- Kirby-Bauer method
- paper disc have some set of Abx, Abx diffuse outward
Result: diameter of zone of inhibition correspond to antimicrobial activity

(3) E-test:
- E test strip graduated with increasing abx conc
- Result: MIC read where growth intersects the strip
- strip is placed on a agar plate growing a microorganism, and MIC is the value that intersects with the strip

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4
Q

AST: breakpoints

definition of breakpoints

A

critical conc which predict susceptibility/resistance

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5
Q

AST: what is an antibiogram

A

cumulative susceptibility results

tabulates antimicrobial susceptibility of common bacterial isolates collected in a hospital/institution

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6
Q

differentiate bet pathogen, contaminants and colonisers

A

pathogen: damage host tissue, elicit a host response, sign and symptoms of infection
- can be part of normal flora or from env

colonisers:
- normal flora/pathogenic organism without eliciting a host response

contaminants:
- during collection or processing of host specimens w/o evidence of host response

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7
Q

name common bacterial pathogens and list treatment of choice (overview on antimicrobial spectrum of activity)

A

the table they gave us, pg42

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8
Q

some limitations of doing in vitro to find breakpoint and MIC

A

MIC of diff drugs against a particular organism not directly comparable

lowest MIC reported doesnt necessarily mean best treatment option (doesnt consider conc)

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9
Q

why in vitro AST isnt a good estimate of in vivo activity?

A

doesnt consider

  • patient immune system
  • protein binding of drug
  • ability of drug to reach site of infection
  • drainage/removal of infected foci (infection)
  • DDI
  • some bacteria may only express enzymes that inhibit Abx in vivo
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10
Q

likely contaminant from blood culture:

A

Stap epidermidis, bacillus spp

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11
Q

likely coloniser from urine culture

A

yeast

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12
Q

for antibiogram; in the case of low susceptibility for many drugs, what are the treatment options

A

use a combination of drugs

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13
Q

some limitations of doing in vitro to find breakpoint and MIC

A

MIC of diff drugs against a particular organism not directly comparable

lowest MIC reported doesn’t necessarily mean best treatment option (doesn’t consider conc)

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14
Q

MSSA and MRSA at which body locations?

A

skin, bone, joint, IV lines, bloodstream, implants, heart valves, lungs

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15
Q

Streptococcus at which body locations?

A

skin, bone, joint, bloodstream

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16
Q

Streptococcus pneumoniae at which body locations?

A

CAP

Brain, ENT, lungs, bloodstream

17
Q

Enterococcus faecalis at which body locations?

A

bloodstream, heart valves, abdomen, GI, UT

18
Q

Peptostreptococcus

A

skin, mouth

19
Q

C. difficile

A

abdomen, GI

20
Q

Bacteroides fragilis

A

abdomen, GI

21
Q

H. influenza

A

ENT, lungs

22
Q

E. coli, Kleb sp

A

abdomen, GI, UT, bloodstream, DM foot

23
Q

ESBL‐producing Ecoli, Kleb

A

per Ecoli, Kleb, more likely hospital-acquired, multiple antibiotic use

24
Q

Enterobacter (Amp‐C producing GNR)

A

abdomen, urinary tract, bloodstream, DFI

25
Q

P. aeruginosa

A

lung, UT, bloodstream, device-related, DFI

26
Q

what are the normal sterile sites?

A

(1) CV system
(2) CNS
(3) Lower respiratory tract
(4) Bone, joint
(5) genitourinary tract (except urethra and vagina)

27
Q

gram stains of stap spp., s.pneumoniae, streptococcus, Ecoli

A

(1) stap spp.: gram +ve cocci in clusters (purple)
(2) s.pneumoniae: gram +ve diplococcus (purple)
(3) streptococcus: gram +ve cocci in chains (purple)
(4) E coli: gram -ve rod (red)

28
Q

site of infections of atypical

A

ENT, lungs

29
Q

3 categories of breakpoints and what they mean

A

(1) susceptible = likely therapeutic success with the dosage given
(2) intermediate = uncertain response; drug has to be physically concentrated or high dosage used
(3) Resistant = likely therapeutic failure

30
Q

uses of antibiogram

A
  • tells the local susceptibility rates
  • monitors resistance trends over time
  • guide selection of treatment when culture and susceptibility results are UNAVAILABLE
31
Q

categories of bacteria

A

s.aureus: gram +ve, aerobic, cluster, (+) coagulase, cocci

streptococci (A,B) - s.pyogenes or s.agalactiae : gram +ve, aerobic, in chains, beta-hemolysis, cocci

s.pneumoniae and Enterococcus fecalis: +ve, aerobic, in chains, alpha/gamma hemolysis, cocci

Bacteroides: gram -ve, anaerobic, bacilli

Enterobacteriaceae: gram -ve, bacilli, aerobic, lactose fermenter, (-ve) oxidase

Acinetobacter: -ve, bacilli, aerobic, non-lactose fermenter, (-ve) oxidase

Pseudomonas: -ve, bacilli, aerobic, non-lactose fermenter, (+ve) oxidase