Chapter 11


Defining and Differential Properties of Enteric Bacteria


1. Structure

2. Biochemical and growth properties

3. Serologic classification

Virulence factors

1. Endotoxin, a part of the LPS produced by all Enterobacteriaceae, is responsible for many of the systemic manifestations of infection.

2. Exotoxins, produced by some species and strains, cause diarrhea.

3. Adhesins and fimbriae on some species promote adhesion to the colon, bladder, or other tissues.

4. Intracellular growth (Shigella, Salmonella and Yersinia species and enteroinvasive Escherichia coli) protects organisms from host defenses.

5. Antibiotic resistance develops rapidly and often is encoded on plasmids, which can be transferred to related bacteria.

6. Capsule on Klebsiella and Salmonella species is antiphagocytic.

7. The genes for many of the virulence factors are clustered and coordinately controlled within pathogenicity islands.

Distribution and infection (Table 11-2)

1. Enterobacteriaceae are found worldwide in soil, water, and vegetation.

2. They are part of the normal intestinal flora of animals and humans.

3. Human pathogens

4. Opportunistic organisms

II Lactose-Fermenting Enterobacteriaceae

E. coli

1. Pathogenesis

a. Endotoxin is present in all strains

b. Noncytotoxic enterotoxins: enterotoxigenic strains (ETEC)

c. Enterohemorrhagic strains (EHEC)

d. Enteroinvasive strains (EIEC)

e. Enteropathogenic strains (EPEC) and enteroaggregative strains (EAEC)

f. Uropathogenic stains (UPEC)

2. Diseases caused by E. coli

• Gastroenteritis

• Hemolytic-uremic syndrome

Jun 18, 2016 | Posted by in IMMUNOLOGY | Comments Off on Enterobacteriaceae

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