Comprehensive Micro Review

NF on skin

coag neg staph

corynebacterium

cutibacterium acnes

micrococci

strep viridans

(transient/colonizers of skin)

vaginal NF

lactobacilli

low numbers of anaerobes and skin flora

normal GI flora

enterobacterales

anaerobes

enterococcus

lactobacilli

respiratory NF

anaerobes

saprophytic neisseria

strep viridans group

GPC (staph, rothia, nutritionallu varient strep)

corynebacterium

strep penumoniae, moraxella, H. influenzae, and yeast (in small amounts)

should there be NF in the blood

no

should there be NF in the body fluids

no

should there be NF in the urine

no (but it’s often contaminated)

common pathogens in urine cultures

enterobacterales

enterococci

S. aureus

S. saprophyticus (young females)

Pseudomonas

pathogens in the genital cultures

clue cells caused by bacterial vaginosis

N. gonorrhoeae, Group B Strep, and yeast (in any amount)

pathogens in stool cultures

salmonella

shigella

campylobacter

pathogens in throat cultures (upper)

S. pyogenes

pathogens in lower respiratory cultures (sputum)

S. pneumoniae

H. influenzae

Moraxella catarrhalis

S. aureus, Enterobacterales, Pseudomonas, and Acinetobacter (when predominant)

pathogens in wound cultures

S. aureus

S. pyogenes (and other beta-strep)

Enterococcus

Anaerobes (esp B, fragilis, Prevotella, and Clostridium)

Enterobacterales

Non-fermenters

Candida spp.

pathogens in the body fluids (CSF)

Group B Strep (neonates)

N. meningitidis (young adults)

S. pneumoniae

Listeria

E coli

H. influenzae

Cryptococcus

pathogens in the body fluids (pleural fluid)

S. pneumoniae

S. aureus

H. influenzae

P. aeruginosa

pathogens in the body fluids (peritoneal fluid)

Enterobacterales

anaerobes

S. viridans group

Enterococcus

pathogens in the body fluids (pericardial fluid)

most often viral

S. aureus

Strep viridans group

pathogens in the body fluids (synovial fluid)

S. aureus

N. gonorrhoeae

coag negative staph

corynebacterium

cutibacterium

pathogens in the blood

coag negative staph

corynebacterium

cutibacterium acnes

micrococci

strep viridans group

bacillus

plates set up for wound culture

aerobic BAP, CHOC, PEA, and LKV

anaerobic ABAP, APEA, and LKV

plates set up for body fluids

BAP and CHOC

what plate do you set up if you’ve seen yeast on the gram stain

SAB plate

plates set up for sputum

BAP, CHOC, and MAC

why do we place an optochin disk on a BAP plate when doing a sputum culture

to identify Streptococcus pneumoniae ( it’s sensitive to optochin)

what plates do we set up for a blood culture

BAP, CHOC, and MAC if you see GNB in the blood smear

ABAP if you have an anaerobic bottle

what plates do you set up for a urine culture

BAP and MAC

what plates do you set up for a genital culture

BAP, CHOC, MAC, and TM

what plates do you set up for a stool culture

BAP, MAC, XLD, and CAMPY

what is a TM plate used to identify

Neiserria species

what is the PEA plate used for

to identify gram positive bacteria

what is XLD used to identify

salmonella or shigella

what is a CAMPY plate used to identify

Campylobacter species

what is an LKV plate used to identify

anaerobic species

what is a BBE plate used to identify

B. fragilis

what would you do next

gram stain or do the catalase test

if you catalase is (+) and the gram stain shows GPC what next step would you take

do the coagulase

if your catalase is (+) and the gram stain shows GPC, and coagulase is (+) what organism would this be

Staphylococcus aureus

what suspectibility testing could you do for S. aureus

penicillin or cefoxitin

if your cefoxitin is resistant what organism would that be

MRSA

what next steps would you take

gram stain or preform catalase

if your catalase is (+) then what next step would you take

coagulase

if your catalse is (+) and coagulase is (-) what would the organism be

coag negative staph

what would you do next

gram stain to look for tetrads and do catalase

if you see tetrads and the catalase is (+) what would you do next

microdase test (should be blue or purple for +)

what organism is this

Rothia mucilaginosa

what next steps would you take

beta hemolysis so catalase and then Lancefield Grouping (probably Group A)

what next steps would you take

know it’s alpha so bile solubility

if bile solubility is (+) meaning the colonies lyse what organism is this

S. pneumoniae

lets say you subbed alpha hemolysis to a new plate and put an optochin disk on the plate, and did bile solubility and it was (-) , what does this result tell you

optochin resistant so most likely S. viridans which is normal flora

what next steps should you take

beta hemolysis so gram stain and catalase

lets say the gram stain showed GPC and was catalase (-) what should you do next

PYR

lets say the gram stain showed GPC, was catalase (-), and was PYR (+), what would the organism be

Enterococcus (if you did bile esculin it would show black)

what would you do next

gram stain

lets say the gram stain showed GPB that were stacking, what organism would this be

Corynebacterium

what would you do next

beta hemolysis so gram stain and catalase

lets say the gram stain showed GPB with beta from a blood culture and was catalase (+) what is most likely the organism

Listeria monocytogenes

what organism is this most likely

alpha hemolysis and GPB so Lactobacillus

what does this CSF culture show

yeast

you saw yeast in your gram stain from your BAP so you put it onto an SAB plate and saw this, what next step would you take

india ink to confirm Cryptococcus neoformans

this is from a respiratory culture so what would you do next

there’s more growth on CHOC so gram stain the CHOC

lets say you gram stained your respiratory culture and saw GNCB, what next step would you take

subculture to a quad plate

lets say you subcultured from you respiratory plate onto a quad plate and saw this, what is most likely the organism

H. influenzae

what next steps would you take

know it’s a lactose fermenter so indole

lets say the indole was (+) and you ended up doing a citrate tube and it was (-), what organism would this be

E. coli

is this a UTI

noa UTI is characterized by specific symptoms and typically involves the urinary tract.

what next steps would you take

lactose fermenter so would do indole

lets say your indole was (-), what next step would you take

API strip

lets say your API strip showed indole (-), citrate (+) and urease (+), what organism would it be

Klebisiella pneumoniae

what next steps would you take

swarming present and non-lactose fermenter so oxidase

lets say the oxidase was (-), what next steps would you take

API strip

your oxidase is (-) and lets say your API strip showed H₂S (+), urease (+), and TDA (+), what organism is this most likely

Proteus mirabilus

what next steps would you take

preform an oxidase because the organism doesn’t ferment lactose

lets say your oxidase is positive and it’s also motile, what organism is this

P. aeruginosa

what next steps would you do

gram stain

lets say the gram stain showed GNB, what step would you take next

oxidase and API strip

lets say your GNB was oxidase (-) and your API strip showed glucose (-), what organism is this

Acinetobacter lwoffi

lets say your plate showed a GNCB that was oxidase (-), and nomotile but on the API strip it showed glucose (+), what organism is this

Acinetobacter baumanni

this is a wound culture that has grown on your ABAP and LKV but not your BAP, what does this mean and what next step would you take

it’s an obligate anaerobe, gram stain

lets say your gram stain showed GNB so you sub-cultured to a BBE plate and saw this, what organism would this be

B. fragilis

lets say your gram stain showed GNB so you sub-cultured to a BBE plate but instead of black you saw clear growth, what organism would this be

Prevotella

lets say you saw this on your ABAP, there was no growth on the LKV, and gram stained and saw GPB, what organism would this be

Clostridium perfringens

how would you work up S. saprophyticus

make sure the patient is a young female and it’s a urine culture

preform a catalase (+)

preform a coagulase (-)

preform novobiocin susceptibility (R)

how to work up N. gonorrhoeae

preform isolation on TM and look for growth or gram stain to see GNDC

if growth perform NH strip to confirm or NAAT

how to work up Salmonella

isolate on selective media (XLD) should be black because of H₂S production

indole (-)

API strip

how to work up Shigella

isolate on selective media (XLD) should show red colonies

indole (V)

API strip

how to work up Campylobacter

isolate on CAMPY

gram stain (shows seagull shape)

motility and oxidase (+)

what organism is this

Cutibacterium acnes

lets say you’re given these results:

oxidase (-)

nonmotile

glucose oxidizer

on BAP it looks yellow-white, on MAC it’s clear

Acinetobacter

how would you work up Acinetobacter

isolate on BAP and MAC, perform oxidase test and motility test

clue cells are indicative of

garderella vaginalis

lets say your given these results:

lower respiratory culture

GNCB

butyrate esterase (+)

Moraxella cattarrhalis

lets say you’re given these results:

BAP has white growth, MAC has pink

indole (-)

citrate (+)

urease (+)

Klebsiella pneumoniae

lets say you’re given these results:

BAP has white growth, MAC has pink growth

indole (+)

citrate (-)

E. coli

lets say you’re given these results:

obligate anaerobe

beta on ABAP, growth on APEA, and no growth on LKV

GPB

Clostridium perfringens

what test can you preform to rule out/in S. pneumoniae

bile solubility

let’s say you’re given these results:

shiny/metallic on BAP, clear on MAC

oxidase (+)

motile

P. aeruginosa

lets say you’re given these results:

BAP has white growth

MAC has clear growth

XLD has black growth with hot pink background

Salmonella

lets say you’re given these results:

BAP has yellow-white growth and is beta

catalase (+)

coagulase (+)

S. aureus

Proteus mirabilus is indole

negative

Proteus vulgaris is indole

positive