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3124 ca2 > AMR and clinical microbio > Flashcards

AMR and clinical microbio Flashcards

1
Q

2 causes of resistance and what they mean

A
  1. mutation
    some mutations make bacteria resistant to drugs
    , only resistant bacteria survive and those multiply and thrive
  2. gene transfer
    bacteria that may have drug resistant dna can transfer copy of those genes to other bacteria
    = then non resistant bacteria become resistant and
    = multiply and thrive
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2
Q

what is selection pressure

A

every exposure of ab to a microbe exerts selection pressure
= selects for more resistant strains
= which spread

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3
Q

6 sterile sites of the body

A
  1. blood ( altho transient bacteremia normal , can be cleared from our system )
  2. urine if straight from kidney ( pass uretha not sterile )
  3. csf
  4. lower resp tract
  5. bone, joints
    . genitourinary tract except for urethra and vagina
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4
Q

which bacteria causes otitis media

A

streptococcus pneumoniae

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5
Q

which bacteria causes sinusitis

A

streptococcus pneumoniae

haemohilius influenzae

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6
Q

which bacteria causes upper resp tract infection

A

streptococcus pyogenes

haemophilius influenzae

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7
Q

which bacteria causes UTIs

A

ecoli
other enterobacteriaceae
- staphlycoccus saprophyticus
- pseudomonas aeruginosa

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8
Q

which bacteria causes STI

A
  • chlamydia trachomatis
  • neisseria gonorrhoeae
  • treponema pallidum
  • ureaplasma urealyticum
  • haemophilus ducreyi
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9
Q

which bactera cause skin infections

A

staphlococcus aureus
streptococcus pyogenes
pseudomonas aeruginosa

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10
Q

which bacteria causes comm acquired pneumonia (3)

and which cause atypical pneumonia (4)

A

comm acquired

  • streptococcus pneumoniae
  • haemophilus influenzae
  • straphylococcus aureus

atypical :

  • mycoplasma pneumoniae
  • chlamydia pneumoniae
  • legionella pneumophila tubercolosis
  • mycobacterium tubercolosis
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11
Q

diff methods of microscopy diagnosis and what is it for

A

-light, fluorescence , electron
- direct, differential stain eg gram stain or acid fast , fluorescent stain
for -> identifying org

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12
Q

describe gram stain process

A

gram pos- purple - retains colour bc of thick peptidoglycan layer ( p to p )
gram neg- red - thin peptidoglycan so picks up counterstain instead

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13
Q

types of culture and what for

A

broth, agar, diff culture mediums

encourages growth of diff organisms

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14
Q

biochem tests

A
  • need specific nutrients eg fermenters, non fermenters

- need specific enzymes eg catalase, coagulase, oxidase

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15
Q

serologic /immunologic diagnostics and what for

A

for –> detecting antigens

eg hep b antigen, hcv antibody, enzyme immunoassay

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16
Q

eg of molecular, nucleic acid based diagnostic

A

for–> amplifying nucleic acid
nucleic acid probes
PCR

17
Q

another eg of diagnostic tool

A

mass spectrometry

18
Q

how long does gram stain take

A

usually avail within 24 hrs

19
Q

what is antimicrobial susceptibility testing (AST)

A

test whether ab active against the bacteria

20
Q

AST can be used when

A
  • isolate is clinically significant eg pathogen
  • specimen collected properly
  • possible resistance to the primary therapeutic agents normally of choice
  • when there are interpretive criteria established to refer to afterwards
21
Q

how to tell MIC from agar/broth dilution method

A

the lowest conc of antimicrobial where there is no visible growth of the organism

eg if until 4mcg/ml of conc there is still growth but at 8mcg/ml no growth then MIC = 8mcg/mL

22
Q

describe the disk diffusion method of AST

aka kirby-bauer disk diffusion method

A

filter paper discs containing set conc of antibiotics
, and the ab diffuses otuwards

diameter ( zone of inhibition correlates with the antimicrobial activity

23
Q

can u get MIC reading from disk diffusion method

A

no bc its a quantitative method not qualitative

24
Q

describe the E-test

A

plastic strip with graduated antibiotic concentrations

where the growth intersects with the strip
=where growth inhibited
= MIC reading
look at pic if need visualise

25
Q

what are the 3 breakpoints and what is recommended

A

S, I , R ( LOOK AT LECT NOTE SLIDE 27)
S- susceptible - likely therapeutic success with that agent

I- intermediate - uncertain response
may be appropriate if drugs are physically conc or if can use high dose
( not 1st choice, if not choice then use )

R- resistant - likely therapeutic failure

26
Q

limitations of AST

A
  • only in vitro testing , mic of diff drugs against a particular organism are not directly comparable
  • lowest mic on ast does not mean best treatment option
27
Q

what can affect in vivo activity ( which limits usefulness of AST which is done in vitro )

A
  • patient immune system
  • protein binding of drugs
  • ability of drug to reach target site
  • drainage or removal of infected foci
  • DDI
  • some bact only express enzymes that inhibit the antibiotic in vivo not in vitro
28
Q

how long does culture take

A

2-3 days

29
Q

how long does identifying the bacteria and AST take

A

3-4 days

30
Q

what does gram stain help with

A

guessing which organism it is

31
Q

pathogen vs coloniser vs contaminant

A

pathogen - causes true infection , damages host tissue and elicits host response
colonisers and contaminants dont cause infections
- no indication for AB
coloniser is normal flora or pathogenic organism that dosent elicit host response
contaminant - acquired during collection or processing of host specimen + no host response

32
Q

normal contaminants from blood culture

A

staphylococcus epidermis , bacillus spp.

normally on the skin so must clean skin first

33
Q

normal coloniser from urine

A

yeast

34
Q

how to differentiate coloniser and contaminant and infection

A
  • is it usually found at the site
  • is it a mixed growth? usually will have both
  • is there sign of invasion of tissue?
  • what are the S&S of infection
  • whats the epidemiology and likelihood of causing the disease
35
Q

when does an infection occur

A

microbes overcome host defense system of the body and invade the tissues

36
Q

whats antibiogram for

A

tabulates susceptibility of common bact isolates in a hosp or instituition

to be used to help choose ab if AST not yet released
empiric therapy !

37
Q

choose what level in antibiogram

A

> 80% susceptibility

38
Q

gram pos flowchart

A

aerobic

clusters :
coagulase (+) - staph aureus

chains
beta hemolysis:
grp A or B streptococci , s.pyogenes, s.agalactiae
alpha or gamma & no hemolysis:
s.penumoniae, s.viridans group, E.faecalis/E.faecium

39
Q

gram neg flow chart

A

bacilli

anaerobic :
bacteriodes fragilis , prevotella/fusobacterium

aerobic:
lactose fermenter , oxidase (-) :
enterobacteriaecae family

non lactose fermenter , ( oxidase +):
pseudomonas

3124 ca2 (5 decks)

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