GI bacteria II Flashcards
What is in MacConkey’s agar that ensure that only intestinal bacteria will grow?
Bile salts
What does the red indicate on MacConkey’s agar?
E.coli (can ferment lactose)
What does the white indicate on MacConkey’s agar? What type of bacteria will do this?
Negative for lactose fermentation
Salmonella, shigella
What does a negative result of an indole test indicate?
(no color change) Salmonella
What does a positive result of an indole test indicate?
(red color) E. Coli, Vibrip
What does a positive result on a hydrogen sulfite test look like? What is the agar used for this?
Black precipitate
S-S agar
What bacteria produces H2S? What does this distinguish between?
Salmonella
Distinguishes between salmonella and shigella
What are the four virotypes of E. coli?
ETEC
EPEC
EHEC
EIEC
What is the gram stain, aerobic/anaerobic and invasive properties of EPEC?
Gram negative
Facultative anaerobe
Moderately invasive
What does EPEC cause? In whom?
Watery diarrhea in children
How does EPEC cause disease? (what is the protein on the bacteria, and what is the protein on the intestinal epithelium? What type of secretion system does it use? Are toxins involved?)
BfpA on epithelial cells binds to intimin on bacteria.
Type III secretion of Tir
No toxins
What is a type III secretion system?
When a bacteria injects stuff directly into host cells
What is the actual cause of damage that EPEC does, if it does not produce toxins?
Destroys epithelial cell microvilli, disrupting water reuptake
Which bacteria utilizes an “attaching and effacing” mechanism?
EPEC
How can you diagnose EPEC? (2)
Culture + lactose fermentation and indole testing
PCR
What is the treatment for EPEC?
Supportive
What is the gram stain, aerobic/anaerobic and invasive properties of ETEC?
Gram negative
Facultative anaerobe
Non-invasive
What disease does ETEC cause?
Travelers’ diarrhea
How does ETEC attach to epithelial cells (protein?)
Via Fimbriae
What are the toxins that ETEC produces? Which is heat stable and which is heat liable?
LT toxin (heat liable) and ST toxin (heat stable)
What type of toxin is the LT-heat liable toxins that ETEC produces? What is its effect?
AB toxin
cAMP upregulator
What type of toxin is the ST-heat stable toxins that ETEC produces? What is its effect?
Non-AB toxin
Increases cGMP