1. The Human Digestive System
Figure 25.1

2. Normal Microbiota Millions of bacteria per ml of saliva
Large numbers in large intestine
100 billion bacteria per gram of feces

3. Defenses
Stomach: Acidic
Small intestine: Paneth cells

4. A Healthy Human Tooth
Figure 25.2

5. Dental Caries (Tooth Decay)
Figure 25.3a

6. Dental Caries (Tooth Decay)
Figure 25.3b

7. The Stages of Tooth Decay
Figure 25.4

8. Bacterial Diseases of the Mouth
Pathogen
Dental caries
Streptococcus mutans
Periodontal disease
Porphyromonas spp.
Acute necrotizing gingivitis
Prevotella intermedia

9. Diseases of Lower Digestive System
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

10. Staphylococcal Food Poisoning
Pathogen
Staphylococcus aureus
Symptoms
Nausea, vomiting, and diarrhea
Intoxication/Infection
Intoxication
Enterotoxin (superantigen)
Diagnosis
Phage typing
Treatment
None

11. Shigellosis (Bacillary Dysentery)
Pathogen
Shigella spp.
Symptoms
Tissue damage and dysentery
Intoxication/Infection
Infection
Endotoxin and Shiga exotoxin
Diagnosis
Isolation of bacteria
Treatment
Quinolones

12. Invasion of Intestinal Wall by Shigella
Figure 25.7

13. Shigellosis
Figure 25.8

14. Salmonellosis and Typhoid Fever
Figure 25.10

15. Typhoid Fever Caused by Salmonella typhi
Bacteria spread throughout body in phagocytes
1–3% of recovered patients become chronic carriers

16. Disease
Salmonellosis
Typhoid Fever
Pathogen
Salmonella enterica
S. typhi
Symptoms
Nausea and diarrhea
High fever, significant mortality
Intoxication/ Infection
Infection
Endotoxin
Diagnosis
Isolation of bacteria; serotyping
Treatment
Oral rehydration
Quinolones; cephalosporins

17. Vibrios Cholera Noncholera vibrios
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

18. Vibrio cholerae
Figure 25.11

19. Vibrio cholerae O:1 and O:139 V. vulnificus
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
Treatment
Rehydration; doxycycline
Rehydration; antibiotics
Antibiotics

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

21. Escherichia coli Gastroenteritis
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

22. Escherichia coli Gastroenteritis
Disease
Traveler’s Diarrhea
STEC
Intoxication/Infection
Infection
Endotoxin
Infection Shiga exotoxin
Diagnosis
Isolation of bacteria
Treatment
Oral rehydration
Quinolones; cephalosporins

23. Helicobacter Peptic Ulcer Disease
Figure 25.13

24. Helicobacter Peptic Ulcer Disease
Pathogen
Helicobacter pylori
Symptoms
Peptic ulcers
Intoxication/Infection
Infection
Diagnosis
Urea breath, bacterial culture
Treatment
Antimicrobial drugs

25. Clostridium and Bacillus Gastroenteritis
Pathogen
C. perfringens
C. difficile
B. cereus
Symptoms
Diarrhea
Diarrhea to colitis
Nausea and vomiting; diarrhea
Intoxication/Infection
Infection
Exotoxin
Intoxication
Diagnosis
Isolation of bacteria
Cytotoxin assay

26. Clostridium and Bacillus Gastroenteritis
Pathogen
C. perfringens
C. difficile
B. cereus
Transmitted
Metronidazole;
discontinue other antibiotic therapy
Source of Infection
Meats
Elimination of normal microbiota
Rice dishes

27. Viral Diseases of the Digestive System
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
EIA
PCR
Treatment
Preventive vaccine
Oral rehydration

28. A Case of Mumps
Figure 25.14

29. Hepatitis An inflammation of the liver
May result from drug or chemical toxicity, EB virus, CMV, or the hepatitis viruses

30. Hepatitis Viruses Disease Transmission Pathogen Chronic Liver Disease?
Vaccine?
Hepatitis A
Fecal-oral
Picornaviridae No
Inactivated virus
Hepatitis B
Parenteral, STI
Hepadnaviridae
Yes
Recombinant
Hepatitis C
Parenteral
Filoviridae
None
Hepatitis D
Pareteral, HBV coinfection
Deltaviridae
HBV vaccine
Hepatitis E
Caliciviridae
HAV vaccine

31. Hepatitis B Virus (HBV)
Figure 25.15