Chapter 25: Microbial Diseases of the Digestive System (Exam 3)

Structures of the Digestive System

-Mouth
-Pharynx
-Esophagus
-Stomach
-Small and large intestine

Where are most normal microbiota found in the human body?

Large intestine

Food infection

-GROWTH takes place in a host
-Incubation: 12 hrs - 2 weeks
-Takes time and hence symptoms appear later

Food intoxication

-Ingestion of toxin (already grown)
-1-48 hrs for symptoms to appear
-Pathogen has already grown and produced toxin

What separates food infection and intoxication?

Time delay in onset of symptoms

Etiology of Staphylococcal Food Poisoning

Staphylococcus aureus

Staphylococcal Food Poisoning Infection or Intoxication?

Intoxication; enterotoxin (superantigen)

Pathogenesis of Staphylococcal Food Poisoning

-Presents in nasal passages or skin lesions
-Important to cook and store food properly
-Competing microbes are eliminated - S. aureus can grow in food
-Toxin is not destroyed during reheating of food

S/S of Staphylococcal Food Poisoning

N/V/D

Etiology of Shigellosis

Shigella spp.

S/S of Shigellosis

Dysentery (damage to intestine walls)

Shigellosis Infection or Intoxication?

Infection; endotoxin and Shiga exotoxin, spreads human to human

Pathogenesis of Shigellosis

-Do not spread in blood
-Infects intestinal lining by entering through M cells
-Spread from one host to another adjacent cell w/o coming out of cell (avoids immune defenses)
-Kill macrophages that phagocytized microbe

Etiology of Salmonellosis

-Salmonella enterica
-G-
-Facultative anaerobe
-Normal inhabitant

S/S of Salmonellosis

N/D

Salmonellosis Infection or intoxication?

Infection

Pathogenesis of Salmonellosis

-Invades intestinal mucosal lining through M cells and multiples
-Associated with commercial chicken and egg production

Diagnosis of Salmonellosis

Isolation of bacteria; serotyping

Treatment of Salmonellosis

Oral rehydration

Etiology of Typhoid Fever

Salmonella typhi

S/S of Typhoid Fever

-High fever
-Significant mortality

Typhoid Fever Infection or Intoxication?

Infection

Pathogenesis of Typhoid Fever

-Spread only by human feces
-Spread in phagocytosis; survive using phagocytes as vehicle
-1-3% chronic carries; harbor organism in gallbladder

Diagnosis of Typhoid Fever

Isolation of bacteria; serotyping

Treatment of Typhoid Fever

Quinolones

Etiology of Cholera

-Vibrio cholerae
-Curved G- w/single flagellum

Transmission of Cholera

Salty waters

Pathogenesis of Cholera

Cholera toxin
-Produces cholera toxin that causes secretion of electrolytes and water and "rice water stools" (watery diarrhea w/epithelial cells)

Gastroenteritis by E. coli

1. Enteropathogenic E.coli (EPEC)
2. Enteroinvasive E.coli (EIEC)
3. Enteroaggregative E.coli (EAEC)
4. Enterohemorrhagic E. coli (EHEC/ STEC)

Enteropathogenic E.coli (EPEC)

-Diarrhea
-Cause the host cells to form pedestals where bacteria attach

Enteroinvasive E.coli (EIEC)

Causes Shigella-like dysentery

Enteroaggregative E.coli (EAEC)

-Only humans
-Produce an enterotoxin causing watery diarrhea

Enterohemorrhagic E. coli (EHEC/ STEC)

-Produces Shiga-like toxin: Released upon the cell's lysis
-Outbreaks are due to E. coli
-Cattle are main reservoir
-Causes hemorrhagic colitis

Etiology of Traveler's Diarrhea

-ETEC (most common)
-enterotoxigenic, enteroinvasive, enteroaggregative E. coli

S/S of Traveler's Diarrhea

Watery diarrhea

Traveler's Diarrhea Infection or intoxication?

Infection

Diagnosis of Traveler's Diarrhea

Isolation of bacteria

Treatment of Traveler's Diarrhea

Oral rehydration

Etiology of Helicobacter Peptic Ulcer Disease

Helicobacter pylori

S/S of Helicobacter Peptic Ulcer Disease

Peptic ulcers (stomach ulcer)

Helicobacter Peptic Ulcer Disease Infection or Intoxication?

Infection

Diagnosis of Helicobacter Peptic Ulcer Disease

Urea breath, bacterial culture

Treatment of Helicobacter Peptic Ulcer Disease

Antimicrobial drugs

Pathogenesis of Helicobacter Peptic Ulcer Disease

-Requires neutral pH - produces enzyme urease which converts urea to alkaline ammonia to counterbalance acidic pH
-Bacterium disrupts stomach mucosa, causing inflammation
-Damage to stomach lining is caused by chronic inflammation and stomach acid leading to erosion of mucous lining
-Leads to ulcers and in some cases stomach cancers

Etiology of Clostridium difficile

-Clostridium difficile
-G+
-Endospore-forming anaerobe

Clostridium difficile causes more...

deaths than all other intestinal infections combined
-mostly hospital setting

Clostridium difficile is....

life threatening colitis
-ulceration and proliferation of the intestinal wall
-precipitated by extended use of antibiotics: antibiotic associated diarrhea