Enteric Bacteria I and II Flashcards
Diarrheal diseases are a much bigger problem in __________ countries.
poor
Which bacteria causes the most diarrheal deaths worldwide?
Shigella (730,000) Salmonella typhi (600,000) Escherichia coli (380,000) Cholera vibrio (120,000)
Note: most deaths are due to viral diarrhea [rotavirus (800,000)]
What is the main route of enteric bacterial infection?
Fecal-oral (often from contaminated poultry, beef, eggs, milk, and vegetables)
The ability to resist acid determines ______________.
infectivity; that is, the more acid-resistant a bacterium is, the fewer bacteria that are needed to cause an infection (so Shigella needs as few as 10 organisms to cause infection)
Which enteric bacteria are acid-labile?
Salmonella and Vibrio (think of the lemon by the salmon and the lemon on the oyster tray in the cholera sketch)
Vibrio cholera grows well on ______________.
alkaline media
Think of the “BASE camp” written on the map in the Colonel Cholera sketch.
In the bacterial nomenclature of O’s and H’s, what do each mean?
O: lipopolysaccharide (which has two O’s; also, lipopolysaccharide is the source of endOtoxin)
H: flagellum (“fla-HELL-um”)
The heat-stable toxin of E. coli raises intracellular ______________.
cGMP (eL Agua de San Gabriel: Labile raises cAMP and Stabile raises cGMP)
Bacteriophage conversion can produce ______________ in a bacterium.
toxin expression
________________ are remnants of foreign DNA that allow bacteria to infect hosts.
Pathogenicity islands
_____________ allow E. coli to infect hosts and demonstrate tropism.
Pili (Sketchy shows this by the ponytails of the girl sitting at the E. Cola diner bar)
What is the difference between bloody diarrhea from dysentery and EHEC?
Dysentery makes smaller volume bloody stools
What external feature of Vibrio cholera allows it to infect humans?
It has fimbriae (toxin co-regulated pilus – TCP) and a flagellum.
(Think of the ROPE tying the cholera raft to the bank of the river in the Colonel Cholera sketch.)
Which enteric bacteria commonly infects shellfish?
Vibrio cholera (like the oysters on Colonel Cholera’s plate)
_________________ allowed cholera to become toxic.
The pili allowed the bacteriophage to dock and infect the cells with the toxin-containing DNA.
Describe the layout and function of cholera toxin.
It has two subunits –A and B. The B unit binds the cell and the A unit acts to increase cAMP. First, though, the dimer must enter the endoplasmic reticulum.
Eschericia coli grows ___________ on EMB agar.
green (like the green coasters in the E. Cola sketch)
Which virulence factor from E. coli causes secretory diarrhea?
Both the heat-labile and heat-stable toxins contribute to the development of secretory diarrhea.
Adherence factor helps ____________ colonize the intestine.
E. coli
Which of E. coli’s toxins is more similar to cholera toxin?
The heat-labile toxin is more similar because they both raise cAMP.
The bacteria that forms pedestals on microvilli has what unique virulence factor (for its species)?
Type III secretion system
(This describes enteropathogenic Eschericia coli –EPEC –P for EPEC and P for Pedestal; it is a common cause of watery diarrhea.)
True or false: EHEC ferments sorbitol.
False. EHEC is non-sorbitol fermenting.
How does the EHEC toxin work?
It inhibits the 60S ribosomal subunit.
(You need to remember two Sketchy mnemonics: the boy in the EHEC sketch is holding the She-Gorilla; and in the Shigella sketch, the gorilla is being timed with the 60-Second hourglass next to the actin cannon.)
True or false: EHEC starts with mucus and blood in the stool.
False. Typically, EHEC starts with watery diarrhea.
When does EHEC typically present (after consumption)?
2-3 days after consumption
Which Shigella strain is the most severe?
Shigella dysenteriae (group A; this is the only kind that can make Shiga toxin)
What allows Shigella strains to become toxic?
Type III secretion systems
In the Sketchy scene, the young ringmaster is holding a turkey baster!
Shigella invades __________ cells.
M (like the M on the She-Gorilla cannon)
What distinguishes M cells from other enterocytes?
They do not have microvilli (M cells are Minus Microvilli)
Why does Shigella cause bleeding?
It secretes IL-8 which attracts neutrophils. The neutrophil invasion secretes damaging proteins and chemicals.
(Think of neutrophils with IL-8 because neutrophils are polymorphonuclear and the number 8 is a bi-lobed symbol.)
Many people write about Salmonella typhi as if it is a unique species, but actually _________________.
it is a serovar of Salmonella enterica (as is S. enteriditis)
What diseases are commonly caused by non-typhoidal S. enteriditis?
In healthy people, S. enteriditis commonly causes watery, self-limited diarrhea. In those with HIV, however, Salmonella can disseminate.
What is the incubation period for Salmonella typhii?
1-3 weeks
How do people shed typhoid without developing symptoms?
S. typhii colonizes the gallbladder and sheds organisms into the stool, but it does not invade.
Salmonella survives by _____________.
triggering its own entry into macrophages
The ______________ of Salmonella allows it to evade phagocytic cells.
capsule (remember the video of the neutrophil trying to get the Salmonella without the capsule)
Campylobacter is often said to be ___________-shaped.
gullwing (honestly, to me, it looks like a mustache)
Think of the mustache on the camper in the Skethcy scene.
Campylobacter outbreaks are often associated with _________________.
raw milk, uncooked poultry (individual cases), and contaminated water
Sketchy left out a couple important features of Campylobacter: _______________.
it has flagella and it colonizes the distal ileum
Describe Helicobacter.
Gram-negative (red helicopter) Motile (moving helicopter rotors) Urease-positive (pilot cleaning his windshield with ammonia) Multi-flagellated Oxidase-positive (pilot's ring) Curved (pilot's mustache)
Campylobacter is catalase-_____________.
positive
Sketchy notably omitted this, but I saw it in lab and online!
What is the K antigen?
The capsule (“kapsule”)
Remember the encapsulated Kake in the E. coli sketch.
How does cholera toxin activate Gs?
By ribosylating it
Imagine a bow on Colonel Cholera.
What diarrhea is typical of EPEC?
Persistent watery
ePec = Persistent diarrhea
True or false: E. coli cannot survive in anaerobic conditions.
False. E. coli is a facultative anaerobe.
Shigella is a human-adapted organism, while ____________ is not and passes from species to species.
Salmonella
Like Shigella, Salmonella also _______________.
invades M cells first and then invades macrophages
Think of the M on the cages above the fowl.
_______________ is the most common cause of bacterial gastroenteritis in the western world.
Campylobacter
Campylobacter can cause _____________ in individuals with HLA-B27.
reactive arthritis
Severe ETEC or V. cholerae can be treated with ________________.
fluoroquinolones
