Enterobacteriaceae

Question 1

Enterobacteriaceae (4):

Answer 1

• Gram negative rods.
• LPS in cell wall.
• Ferment glucose.
• Oxidase negative

Question 2

Enterobacteriaceae that ferment lactose (5):

Answer 2

Occurs:
- Klebsiella.
- Escherichia
- Enterobacter
Slowly:
- Serratia
- Vibrio

Question 3

Enterobacteriaceae virulence factors (7):

Answer 3

• Endotoxin (LPS - highly immunogenic).
• Capsule.
• Antigenic phase variation.
• Type III secretion system.
• Sequestration of growth factor.
• Resistance to serum killing (compliment).
• Antimicrobial resistance.

Question 4

Diseases caused by E. coli (5):

Answer 4

• Gastroenteritis.
• Hemolytic-uremic syndrome.
• UTI.
• Neonatal meningitis.
• Septicemia.

Question 5

Five major E. coli groups (5):

Answer 5

• ETEC
• EPEC
• EIEC
• EAggEC
• EHEC

Question 6

ETEC (6):

Answer 6

• Plasmid-mediated.
• Non-invasive.
• Fimbrial adhesins, CFA I and II.
• Heat labile (LT) and heat stable (ST) enterotoxins.
• Watery diarrhea in infants and traveler’s diarrhea.
• No inflammation, fever or cell cytotoxicity.

Question 7

EPEC (7):

Answer 7

• Non-fimbrial adhesion.
• Moderately invasive.
• Does not produce LT or ST.
• Attachement-effacement.
• Bundle forming pilus (Bfp).
• Destruction of microvilli.
• Infantile diarrhea, some inflammation, no fever.

Question 8

EHEC (4):

Answer 8

• Moderately invasive.
• Does not produce LT or ST.
• Produces shiga-like toxin (SLT) - cytotoxic to intestinal villi and colon epithelial cells.
• Pediatric diarrhea, copious bloody discharge, intense inflammation and hemolytic uremia.

Question 9

EIEC (6):

Answer 9

• Non-fimbrial adhesions.
• Invasive.
• Entry site is the M cell.
• Does not produce shiga toxin.
• Dysentery-like diarrhea (mucous, blood), severe inflammation, fever.
• Very large plasmid.

Question 10

EAggEC (4):

Answer 10

• Adhesins not characterized.
• Non-invasive.
• Produce ST-like toxin and a hemolysin.
• Persistent diarrhea in young children without immunization, no fever.

Question 11

Most common cause of UTI:

Answer 11

E. coli

Question 12

Salmonella spp (4):

Answer 12

• Common in GI tract of animals but not humans.
• Do not ferment lactose.
• Produce H2S.
• Facultative intracellular growth.

Question 13

Diseases caused by salmonella spp (4):

Answer 13

• Gastroenteritis.
• Typhoid (enteric) fever (s. typhi).
• Bacteremia.
• Localized infections in other sites (usually immunocompromised).

Question 14

Typhoid fever (6):

Answer 14

• S. typhi and S. paratyphi.
• 6-30 days incubation.
• Initial symptoms: fever, HA, malaise and anorexia.
• Starts in small intestine through peyer’s patches, then spread to phagocytes of liver, gallbladder and spleen.
• Survival in the phagosomes in phagocytic cells - carrier state.
• Transmitted only by humans.

Question 15

Enterocolitis (4):

Answer 15

• Invasion of epithelia and sub-epithelial tissue of the small and large intestines.
• PMN response limits to the gut and adjacent lymph node.
• Infective dose very high.
• Gastric acid important host defense.

Question 16

Shigella spp (7):

Answer 16

• Non-lactose fermenting.
• Gram-negative rods.
• Do not produce H2S.
• Non-motile.
• Produce no gas fermenting glucose.
• Shiga toxin.
• No animal reservoir.

Question 17

Reiter’s Syndrome (3):

Answer 17

• Arthritis, conjunctivitis and urethritis.
• Appear after intestinal infections by one of the intestinal pathogens.
• Most male, HLA-B27.

Question 18

Pathogens that cause Reiter’s syndrome (5):

Answer 18

• Shigella.
• Yersinia enterocolitica.
• Salmonella.
• Klebsiella pneumoniae.
• Campylobacter.