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Infectious Agents > Exam 3: Gram-negative Rods Part 1: Enterobacteriaceae > Flashcards

Exam 3: Gram-negative Rods Part 1: Enterobacteriaceae Flashcards

1
Q

What are the different types of proteobacteria?

A

Alphaproteobacteria
Betaproteobacteria
Gammaproteobacteria

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2
Q

What is enterobacteriaceae?

A

A large and diverse family of gram negative rods found free living and as part of the indigenous flora of people and animals

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3
Q

How do enterobacteriaceae grow?

A

Rapidly under aerobic and anaerobic conditions and are metabolically active

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4
Q

What is enterobacteriaceae a primary inhabitant of?

A

Lower GI tract

It is the main facultative anaerobic portion of the bacterial content of the cecum and colon

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5
Q

What are other places that enterobacteriaceae can be found?

A

Female genital tract
Transient colonizers of the skin and oral cavity
Small numbers may be present in the respiratory tract of healthy animals

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6
Q

What is the most common species of enterobacteriaceae among the indigenous flora of mammals and some birds?

A

E. coli

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7
Q

What is the morphology of enterobacteriaceae?

A

Medium-sized gram negative rods

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8
Q

What is used for the identification and subtyping of enterobacteriaceae?

A

LPS, capsule/slime layer, and flagellar antigens

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9
Q

What is flagella called as antigenic determinants?

A

H antigens

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10
Q

What are cell surface polysaccharide (capsule, slime layer) antigens called?

A

K antigens

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11
Q

What does LPS contain?

A

O polysaccharide chains called O antigens

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12
Q

What are features of enterobacteriaceae that contribute to classification?

A

All are facultative anaerobes
All ferment glucose
All reduce nitrates to nitrite
All are cytochrome oxidase negative

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13
Q

What is a useful characteristic for initial differentiation of enterobacteriaceae?

A

Rapid fermentation of lactose

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14
Q

What are the toxins of enterobacteriaceae?

A

All possess LPS and its effects are often seen in infections

Some produce exotoxins

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15
Q

Describe the pathogenicity of enterobacteriaceae

A

Some species have unique pathogenic features that allow them to produce GI or systemic infections in previously healthy animals
Most do no infect unless predisposing infections occur

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16
Q

What are the most common sites of opportunistic infections with enterobacteriaceae?

A

Wound and urogenital tract infections, but they may occur at any body site, especially in septicemia

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17
Q

What makes enterobacteriaceae the most variable of all bacteria in susceptibility to antimicrobial agents?

A

Combination of chromosomal and plasmid-mediated resistance

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18
Q

What is enterobacteriaceae usually resistant to?

A

High concentration of penicillin G, erythromycin, and clindamycin

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19
Q

What is E. coli the dominant species of in aerobic culture?

A

Feces or intestinal yields

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20
Q

What are the major diseases caused by E. coli?

A

Enteric infections
Septicemia
Urinary tract infections
Mastitis

21
Q

What are the various schemes that E. coli can be identified by?

A 
Biotyping
Serotyping
Phage-typing
Colicin-typing
Virulence factor expression
22
Q

How many O, K, and H antigens have been identified with E. coli with serotyping?

A

174 O antigens
80 K antigens
53 H antigens

23
Q

What are the 6 classes of E. coli that cause diarrheal disease?

A 
Enterotoxigenic E. coli (ETEC)
Enteroinvasive E. coli (EIEC)
Enterohemorrhagic E. coli (EHEC)
Enteropathogenic E. coli (EPEC)
Enteroaggregative E. coli (EAEC)
Adherent-invasive E. coli (AIEC)
24
Q

What is ETEC an important cause of?

A

Diarrhea in infants and travelers in regions of poor sanitation

25
Q

What is the clinical sign of ETEC?

A

Diarrhea without fever

26
Q

What does ETEC require?

A

Fibriae-mediated colonization and elaboration of one or more enterotoxins (ST or LT)

27
Q

What does EPEC induce?

A

Watery diarrhea similar to ETEC

28
Q

What is the adherence of EPEC strains to the intestinal mucosa due to?

A

Rearrangements of actin in the vicinity of adherent bacteria to form “attaching and effacing” lesions

29
Q

What does EHEC cause?

A

A diarrheal syndrome distinct from EIEC in that there is copious bloody discharge and no fever

30
Q

What is the most well-known EHEC serotype?

A

O157:H7

31
Q

What does EIEC cause?

A

Dysentery-like diarrhea in humans with fever

32
Q

What is the mechanism EIEC?

A

It penetrates and multiplies within epithelial cells of the colon causing widespread cell destruction

33
Q

What does EIEC apparently lack?

A

Fimbrial adhesins, LT or ST toxin, and shiga toxin

34
Q

What is the distinguishing factor of EAEC strains?

A

Their ability to attach to tissue culture cells in an aggregative manner

35
Q

What are EAEC strains associated with?

A

Persistent diarrhea in young children

36
Q

What is AIEC associated with?

A

Crohn’s disease in humans
Histiocytic ulcerative colitis in dogs
Chronic bloody-mucoid diarrhea and weight loss

37
Q

What does flagella of uropathogenic E. coli contribute to?

A

UTI colonization

38
Q

What does flagella of enterotoxigenic E. coli contribute to?

A

Adhesion

39
Q

What are most septicemias in people caused by?

A

Strains with K1 capsular polysaccharide

40
Q

What does K1 do?

A

Enhances invasiveness and increases resistance to phagocytosis and serum killing

41
Q

What does LPS contribute to?

A

Septicemic disease

42
Q

What is fimbriae an essential virulence factor in E. coli for?

A

Adherence to host cell surfaces

43
Q

What does fimbriae do in enterotoxigenic E. coli?

A

Mediates adherence to glycoproteins on the surface of intestinal epithelial cells

44
Q

What are the primary types of enterotoxins?

A

LT and ST

45
Q

What are LT and ST essential virulence factors for along with fibriae?

A

ETEC

46
Q

What is shiga toxin?

A

A heat-labile high MW toxin produced by Shigella dysenteriae

47
Q

What is alpha-hemolysin?

A

RTX toxin frequently produced by certain porcine E. coli

It damages cell membranes

48
Q

What has type III secretion system?

A

EPEC

Infectious Agents (38 decks)

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