Enteropathogenic Bacterial Infections

Question 1

Escherichia coli

Answer 1

• aerobic, G-
• causes over 90% UTIs and leading cause of diarrheal disease
• opportunistic - causes pneumonia and sepsis in immunocompromised and meningitis and sepsis in newborns

Question 2

Enterotoxigenic E. coli

Answer 2

• traveler’s diarrhea

Question 3

Enteropathogenic E. coli

Answer 3

• major cause of diarrheal illness in poor tropical areas in infants and young children

Question 4

Enterohemorrhagic E. coli

Answer 4

• bloody diarrhea, can be followed by hemolytic-uremic syndrome
• source is usually contaminated milk or meat
• destroys epithelial cells

Question 5

Enteroinvasive E. coli

Answer 5

• foodborne dysentery

- similarities to Shigella

Question 6

E, coli UTI

Answer 6

• most common in sexually active women or those with structural/functional abnormalities of urinary tract
• derive from resident flora of perineum and periurethral areas
• produce urgency, pain on urination

Question 7

E. coli pneumonia

Answer 7

• enteric G- bacteria, opportunistic infection

- often caused by aspiration of organisms

Question 8

E. coli sepsis

Answer 8

• G- rods
• opportunistic infection due to impaired ability to eliminate low level bacteremias
• septic shock via TNF stimulated by bacterial endotoxin

Question 9

Neonatal E. coli meningitis and sepsis

Answer 9

• E. coli and group B strep - main causes of meningitis or sepsis in first month after birth
• both colonize in vagina, go to infant GI tract then bloodstream

Question 10

Salmonella enterocolitis

Answer 10

• G- rod
• acute self limited GI illness
• acquired by eating food with nontyphoidal Salmonella strains
• spread via fecal-oral route
• diarrhea 12-48 hrs after consuming food
• tx: supportive (no abx)

Question 11

Typhoid fever

Answer 11

• Salmonella typhi
• typically infects older women with gallstones or biliary scarring
• spread by ingesting contaminated food, especially dairy products and shellfish
• engulfed and multiply within phagocytes, then stimulates IL-1 and TNF
• ulcers located along Peyer’s patches
• forms granulomas on organs (typhoid nodules)
  1) Incubation: 1-14 days
  2) Active invastion/bacteremia: nonspecific symptoms (fever, malaise, HA, arthralgias, pain)
  3) Fastigium: increase in fever/malaise, may become toxic from endotoxins, hepatomegaly, splenomegaly
  4) Lysis: fever/toxic symptoms diminish. GI bleeding.
  5) Convalescence: Recovery with chance of relapse
• tx: Abx, supportive care

Question 12

Shigellosis

Answer 12

• aerobic, G- rods
• S. dysenteriae is most virulent
• presents with abdominal pain and bloody, mucoid stools
• fecal-oral spread
• most common in areas with poor hygiene and sanitation
• most virulent enteropathogens
• produce potent shiga toxin that interferes with 60S ribosomal subunits

Question 13

Cholera

Answer 13

• Vibrio cholerae, aerobic curved G- rod
• proliferates in lumen of small intestine
• causes profuse watery diarrhea, rapid dehydration, shock and death within 24 hrs
• acquired by ingestion of contaminated food or water
• shellfish accounts for most cases in US
• causes massive rise in cAMP which upsets balance of water and sodium
• infected adults can lose up to 20L of fluid/day

Question 14

Vibrio parahaemolyticus

Answer 14

• G- bacillus

- causes acute gastroenteritis

Question 15

Campylobacter jejuni

Answer 15

• microaerophilic curved G- rod
• most common cause of bacterial diarrhea in developed world
• contaminated food or water
• fecal-oral spread, can cause traveler’s diarrhea
• have been associated with Guillain-Barre syndrome

Question 16

Yersinia

Answer 16

• Y. enterocolitica and Y. pseudotuberculosis, G- coccoid
• facultative anaerobes
• causes painful diarrhea