Term
| How do Enterobacteriaceae Gram stain, what shapre are they, are they anaerobic or aerobic, and where do they usually live? |
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Definition
| Enterobacteriaceae are gram negative, anaerobic, (mostly) bacilli, and they usually live in the GI of vertebrates or outside of the body in water. |
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Term
| What antigens are used to serotype Enterobacteriaceae species? |
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Definition
H antigen: Flagella
K antigen: Capsule
O antigen: Cell wall |
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Term
| How are the many varieties of E. coli pathotypes generated? |
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Definition
| Horizontal gene transfer. |
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Term
| Name 2 ways by which nonpathogenic E. coli can benefit humans. |
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Definition
- E. coli contribute to colonization resistance by other pathogenic bacteria, ex - C. diff
- E. coli produce beneficial metabolites in the gut
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Term
| Name 6 diarrheagenic stains of E. coli |
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Definition
- Enterotoxigenic (ETEC)
- Enteropathogenic (EPEC)
- Enterohemorrhagic (EHEC) and other Shiga toxin producing (STEC)
- Enteroaggregative (EAEC)
- Enteroinvasive (EIEC) and Shigella
- Diffuse Adhereing (DAEC)
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Term
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Definition
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Term
| Name 3 ETEC plasmid virulence factors. |
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Definition
- Colonization Factor Antigens
- Heat-labile enterotoxin
- Heat-stable enterotoxin
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Term
| What do ETEC Colonization Factor Antigens do? |
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Definition
| They bind oligosaccharides of specific host tissues |
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Term
| Name a protein associated with the ETEC colonization factor antigens that contributes to host cell binding. |
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Definition
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Term
| Describe how ETEC heat-labile enterotoxin enters cell. What kind of toxin is it; describe its structure. |
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Definition
Heat-labile enterotoxin is an A-B toxin similar to cholera toxin. First the B pentamer binds to the GM1 GLUT ganglioside on the surface of the epithelial cell. Then one of two things may happen:
- The whole A-B toxin is endocytosed
- the A subunit enters through a pore created by the B-pentamer
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Term
| How does Heat-stable Enterotoxin withstand high heat? |
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Definition
| Disulfide bonds hold the structure together. |
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Term
| How does ETEC Heat-stable enterotoxin alter cell metabolism? |
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Definition
| Heat-stable enterotoxin is an ADP-rybosylase. It ribosylates a G protein into a constitutively on position. This in turn turns on a guanylate cyclase receptor and causes an elevation in cGMP, which leads to an increase in Cl- efflux, and prevention of Na+ influx, thus causing efflux of water into the lumen. |
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Term
How does ETEC Heat-labile enterotoxin alter cell metabolism?
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Definition
| Heat-labile enterotoxin works in a very similar way to heat-stable enterotoxin, however instead of constitutively turning on guanylate cyclase, heat-labile enterotoxin turns on adenylate cyclase. |
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Term
| True or False: Enterotoxigenic E. coli damages intestinal epithelial tissue |
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Definition
| False. It causes self-limited watery diarrhea only. |
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Term
| Enteropathogenic E. coli have two virulence factors: Adherence factors (Bundle Forming Pilus), and Attaching/Effacing factors (Type III secretion system). Which is encoded from a plasmid and which is encoded from a pathogenicity island? |
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Definition
| The Bundle Forming Pilus is encoded on a plasmid, and the Type III secretion system is encoded on a pathogenicity island. |
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