MICRO: Lab Flashcards
Swarming is seen with what type of bugs?
proteus and morganella
What indicates fecal contamination of water?
presence of E. coli
What is the first step in evaluating contamination?
coliform count
How do you distinguish between E. coli and enterobacter/Klebsiella?
all are Lac+, so do an IMViC test
What is IMViC?
Indole production from tryptophan
Methyl red (large amount of acid from glucose)
Voges-Proskaur (acetylmethylcarbinol from glucose)
Citrate utilizaiton
What bacteria are IMViC ++–?
E coli
What bacteria are IMViC –++?
Enterobacter and Klebsiella
Which organisms do you specifically need to ask lab to culture?
Vibrios, Yersinia, and sometimes Campylobacter (bugs that compete poorly with normal gut flora on typical enteric media)
What bugs is MacConkey agar specific for? How does it do this?
Selective for Gram Negative, Kills off Gram Positive with bile salts and crystal violet
What is MacConkey agar used for?
permit the differentiation of lactose utilizing and lactose non-utilizing bacteria
What bacteria is lactose positive on MacConkey agar? What color?
E. coli (red/pink)
What bacteria are lactose negative on MacConkey agar? What color?
Salmonella and Shigella (white)
What is sorbitol MacConkey agar used for?
identificaiton of EHEC (most other E coli can ferment sorbitol while EHEC cannot)
True or false: fecal specimens are only cultured anaerobically.
FALSE: only cultures aerobically because strict anaerobes account for 95-99% of bacteria in a fecal specimen
Which 3 anaerobes DO cause infection in the GI tract?
C. perfringens
C. diff
C. botulinum
What is EMB agar selective for? How does it do this?
gram negative bacteria (kills off gram positive with eosin and methylene blue)
What does E. coli look like on EMB? Why?
green colonies with metallic shene (strong lactose fermenter)
What do non-lactose fermenters look like on EMB?
colorless colonies
What is SS specific for, how does it do this?
Salmonella and shigella (high concentration of bile salts inhibits growth of gram positives and coliforms)
How do you tell the difference between lactose fermenters and non-lactose fermenters on SS agar?
non-lactose fermenters are clear and lac+ colonies are pink
What is KIA?
Kligler’s iron agar
Waht 3 things are detected by KIA?
fermentation of glucose/lactose
H2S
Gas
What does KIA look like if ONLY glucose is fermented?
slant turns red (alkaline) color
What does KIA look like if lactose is fermented?
slant is yellow (acid)
What does KIA butt look like if organism can ferment glucose or glucose and lactose?
yellow (acid)
What does a KIA look like if H2S is produced?
black precipitate is formed
What does a KIA from a non-fermenter (ex. Pseudomonas) look like?
red slant/red butt
no sugars fermented
What does a KIA from shigella look like?
red slant/ yellow butt
glucose fermented but not lactose
What does a KIA from salmonella look like?
red slant/ black butt with gas
glucose fermented but not lactose, H2S formed
What does a KIA from E. Coli look like?
yellow slant/yellow butt and gas
lactose fermented
What can the indole test used for?
differentiates between shigella (positive) and salmonella (negative)
What is a positive urease agar look like?
red color on slant portion of agar
Which bacteria will have a slide agglutination reaction?
salmonella or shigella (group B or C)
What is the Kirby Bauer method?
way to test antimicrobial sensitivity
