Gram Negative Rods Enterobacteriaceae Lawrence

Question 1

Enterobacteriaceae

Answer 1

• metabolically active and a variety of substrates

- primary inhabitanst of lower GI

Question 2

E. coli

Answer 2

the most common species

Question 3

Salmonella and Shigella

Answer 3

Certain strains of E.coli and Yersinia species are primary pathogens and not part of the normal flora

Question 4

Morphology

Answer 4

• medium sized gram negative rods
• many have fimbriae
• most have capsules and /or slime layer
• cell wall

Question 5

Antigenic structures

Answer 5

LPS, capsule/slime layer, and flagella are flagella (proteins)

Question 6

classification

Answer 6

• many biochemical tests
• facultative anaerobes
• ferment glucose
• reduce nitrates to nitrile
• cytochrome oxidase negative
• the most common members of the intestinal flora ferment lactose promptly in more than 90% of isolates
• many other genera (shigella and Salmonella) are rarely positive

Question 7

Toxins

Answer 7

• all posses LPS (endotoxin)

- Some also produce exotoxins

Question 8

Pathogenicity

Answer 8

• GI or systemic infections
• most common sites of opportunistic infection: wound and urogenital tract infections
• but may occur at any body site, especially in septicemia

Question 9

E. coli occurrence

Answer 9

• causes enteric diseases, septicemis, UTI, and mastitis

- most common isolate of normal flora from opportunistic infections

Question 10

Serotyping

Answer 10

fimbrial antigens as F antigens

used to be K

Question 11

Enteric diseases

Answer 11

six classes of E. coli

Question 12

ETEC

Answer 12

-enterotoxigenic
-cause of diarrhea in infants and travelers
diarrhea without fever
-do not invade, just sit on surface

Question 13

EPEC

Answer 13

• enteropathogenic
• watery diarrhea without fever or blood
• lose a lot of the microvilli
• attach to pedestal, type III secretion, inject toxin into the body
• attach, do not invade

Question 14

EHEC

Answer 14

• enterohemorrhagica
• bloody diarrhea but no fever
• Attach through the pedestal structure, type three secretion system and attach onto the surface
• They produce a shiga toxin, target is the epithelial cells that line the blood vessels and cause hemorrhage
• attach, do not invade

Question 15

EIEC

Answer 15

• enteroinvasive
• penetrate and multiply withinepithelial cells of the colon, causing widespread cell destruction
• lack fimbrial adhesins, LT or ST toxin, and shiga toxin
• cause watery diarrhea with blood and fever and sever pain
• primary pathogen in monkeys

Question 16

EAEC

Answer 16

• enteroaggregative
• form aggregated bricks, do not invade
• persistent diarrhea in kids
• disease associated in livestock

Question 17

AIEC

Answer 17

• adherent-invasive
• chronic diarrhea with blood
• crohn’s disease in humans
• histiocytic ulcerative colitis in dogs

Question 18

Virulence Factors

Answer 18

Flagella, Capsule (K1 enhances invasiveness and increases resistance to phagocytosis and serum killing), LPS (endotoxin), Fimbriae, Exotoxins, iron uptake system, type III secretion system

Question 19

Virulence Factors : Fimbriae

Answer 19

-adherence to host surfaces
-F4, F5, F6, F18, and F41 are important fimbrial types in swine and cattle
-Avian pathogenic E. coli-F1
-ExPEC-F17c- mediates intestinal adherence to initiate infection
Uropathogenic E. coli (UPEC): P fimbriae

Question 20

Virulence factor: exotoxin

Answer 20

-enterotoxins, shiga toxins, alpha-hemolysin (RTX toxin)