Bacteria in Gut Flashcards
What are the two types of enteric pathogens?
ones that always cause disease (shigella)
harmless as long as they remain in GI tract (klebsiella) = opportunistic
What three bacterial structures are involved in serotyping enteric bacteria?
O antigen - LPS of outer membrane = endotoxin
H antigen = flagellum
K antigen - capsule
What are the three components of LPS?
lipid A - responsible for toxic properties
core polysaccharide and O antigen polysaccharide side chain
What do the A and B components of the heat labile toxin of ETEC do?
B - binds to ganglioside and glycoprotein receptors on brush border
A - causes fluid secretion by activating adenylyl cyclase in NAD-dependent manner
What does the ST toxin of ETEC do?
binds to transmembrane guanylate cyclase receptor protein and causes intestinal secretion by increased cGMP
What diseases can E. coli cause outside the GI tract?
UTI
bacteremia and respiratory tract inf
K1 strains - neonatal meningitis
What are other opportunistic pathogens in addition to E. coli?
klebsiella - alcoholics, polysaccharide capsule
enterobacter - contaminated IV lines
serratia - pink-red colonies, indwelling catheters
proteus - UTI, struvite kidney stones
What is the microbiology of salmonella?
don’t ferment lactose
motile w flagella
s. typhi has capsule = Vi antigen –> vaccine
What is the microbiology of shigella?
four species, three don’t ferment lactose
no flagella
dysenteriae type 1 - shiga toxin
What is the microbiology of vibrio cholerae?
O1 and O139 cause epidemic cholera in ppl
oxidase positive, isolated by TCBS agar
single polar flagellum
How does vibrio cholerae survive in brackish waters?
converts from growing cell into dormant one which cannot be grown on laboratory media
What are the non-epidemic vibrio cholerae strains characteristics?
not O1 or O139, no cholera toxin
cause gastroenteritis, septicemia in debilitated persons
What are the non-cholera vibrios?
parahemolyticus - U.S coastline (fish), wound inf, no antimicrobials unless severe
vulnificus - sea water, inf wounds, more virulent –> serious wound inf in chronic dz (1 in 2 die) - ANTIBIOTICS!
What is the microbiology of campylobacter?
zoonosis, jejuni and coli cause gastroenteritis, obligate microaerophiles
