The Human Digestive System

Figure 25.1

Normal Microbiota

Millions of bacteria per ml of saliva Large numbers in large intestine 100 billion bacteria per gram of feces

Defenses

Stomach: Acidic Small intestine: Paneth cells

A Healthy Human Tooth

Figure 25.2

Dental Caries (Tooth Decay)

Figure 25.3a

Dental Caries (Tooth Decay)

Figure 25.3b

The Stages of Tooth Decay

Figure 25.4

Bacterial Diseases of the Mouth

Disease Pathogen

Dental caries Streptococcus mutans

Periodontal disease Porphyromonas spp.

Acute necrotizing gingivitis

Prevotella intermedia

Infection: Growth of a pathogen Incubation is from 12 hours to 2 weeks Fever

Intoxication: Ingestion of toxin Symptoms appear 1 to 48 hours after ingestion

Gastroenteritis: Diarrhea, dysentery Treatment: Oral rehydration therapy

Diseases of Lower Digestive System

Staphylococcal Food Poisoning

Pathogen Staphylococcus aureus

Symptoms Nausea, vomiting, and diarrhea

Intoxication/Infection IntoxicationEnterotoxin (superantigen)

Diagnosis Phage typing

Treatment None

Shigellosis (Bacillary Dysentery)

Pathogen Shigella spp.

Symptoms Tissue damage and dysentery

Intoxication/Infection InfectionEndotoxin and Shiga exotoxin

Diagnosis Isolation of bacteria

Treatment Quinolones

Invasion of Intestinal Wall by Shigella

Figure 25.7

Shigellosis

Figure 25.8

Salmonellosis and Typhoid Fever

Figure 25.10

Typhoid Fever

Caused by Salmonella typhi Bacteria spread throughout body in phagocytes 1–3% of recovered patients become chronic

carriers

Disease Salmonellosis Typhoid Fever

Pathogen Salmonella enterica

S. typhi

Symptoms Nausea and diarrhea

High fever, significant mortality

Intoxication/ Infection

InfectionEndotoxin

InfectionEndotoxin

Diagnosis Isolation of bacteria; serotyping

Isolation of bacteria; serotyping

Treatment Oral rehydration Quinolones; cephalosporins

Vibrios

Cholera Vibrio cholerae serotypes that produce cholera toxin Toxin causes host cells to secrete Cl–, HCO–, and

water

Noncholera vibrios Usually from contaminated crustaceans or mollusks V. cholerae serotypes other than O:1, O:139, eltor V. parahaemolyticus V. vulnificus

Vibrio cholerae

Figure 25.11

Disease Cholera Noncholera vibrios

Pathogen Vibrio cholerae O:1 and O:139

V. parahaemolyticus

V. vulnificus

Symptoms Diarrhea with large water loss

Cholera-like diarrhea, but generally milder

Rapidly spreading tissue destruction

Intoxication/Infection

Cholera toxin (exotoxin)

Infection, enterotoxin

Infection, siderophores

Diagnosis Isolation of bacteria

Isolation of bacteria

Isolation of bacteria

Treatment Rehydration; doxycycline

Rehydration; antibiotics

Antibiotics

Escherichia coli Gastroenteritis

Pathogenic E. coli Attach to intestinal cells with fimbriae Produce toxins May aggregate

Disease Traveler’s Diarrhea STEC

Pathogen Enterotoxigenic, enteroinvasive, enteraggregative E. coli

Shiga-toxin-producing E. coli

Symptoms Watery diarrhea Shigella-like dysentery; hemorrhagic colitis and hemolytic uremic syndrome

Escherichia coli Gastroenteritis

Disease Traveler’s Diarrhea STEC

Intoxication/Infection

InfectionEndotoxin

Infection Shiga exotoxin

Diagnosis Isolation of bacteria Isolation of bacteria

Treatment Oral rehydration Quinolones; cephalosporins

Escherichia coli Gastroenteritis

Helicobacter Peptic Ulcer Disease

Figure 25.13

Helicobacter Peptic Ulcer Disease

Pathogen Helicobacter pylori

Symptoms Peptic ulcers

Intoxication/Infection Infection

Diagnosis Urea breath, bacterial culture

Treatment Antimicrobial drugs

Clostridium and Bacillus Gastroenteritis

Pathogen C. perfringens

C. difficile B. cereus

Symptoms Diarrhea Diarrhea to colitis

Nausea and vomiting; diarrhea

Intoxication/Infection

InfectionExotoxin

InfectionExotoxin

Intoxication

Diagnosis Isolation of bacteria

Cytotoxin assay

Isolation of bacteria

Pathogen C. perfringens

C. difficile B. cereus

Transmitted Metronidazole;discontinue other antibiotic therapy

Source of Infection

Meats Elimination of normal microbiota

Rice dishes

Clostridium and Bacillus Gastroenteritis

Viral Diseases of the Digestive System

Disease Mumps Viral Gastroenteritis

Pathogen Mumps virus Rotavirus Norovirus

Symptoms Swollen parotid glands

Vomiting, diarrhea, 1 wk

Vomiting, diarrhea, 2–3 days

Incubation 16–18 days 1–3 days 14–48 hr

Diagnosis Symptoms EIA PCR

Treatment Preventive vaccine

Oral rehydration

Oral rehydration

A Case of Mumps

Figure 25.14

Hepatitis

An inflammation of the liver May result from drug or chemical toxicity, EB

virus, CMV, or the hepatitis viruses

Disease Transmission PathogenChronic Liver Disease?

Vaccine?

Hepatitis A

Fecal-oral Picornaviridae No Inactivated virus

Hepatitis B

Parenteral, STI Hepadnaviridae Yes Recombinant

Hepatitis C

Parenteral Filoviridae Yes None

Hepatitis D

Pareteral, HBV coinfection

Deltaviridae Yes HBV vaccine

Hepatitis E

Fecal-oral Caliciviridae No HAV vaccine

Hepatitis Viruses

Hepatitis B Virus (HBV)

Figure 25.15