1. Infectious Diseases Affecting the Digestive System
Ch 20
Infectious Diseases Affecting the Digestive System

2. SLOs
List examples of normal microbiota for each part of the gastrointestinal tract Describe the events that lead to dental caries and periodontal disease List the causative agents, suspect foods, signs and symptoms, virulence factors, prevention and treatments for the diseases discussed in class Differentiate between hepatitis A, B, C, D, and E Outline mode of transmission and symptoms of viral gastroenteritis caused by Norovirus and Rotavirus List the causative agent, modes of transmission, symptoms for giardiasis Distinguish the 4 life cycles of parasitic helminths Compare and contrast the helminthic diseases covered.

3. 20.1/2 GI Tract Defenses and Normal Microbiota
Review Anatomy on your own
Heavy load of normal microbiota – Commensals:
>600 bacterial species in mouth
Stomach and small intestine have few resident microbes
Fecal mass: Up to 40% microbial cells
Bacteria in large intestine assist in degrading food and synthesizing vitamins. They also competitively inhibit pathogens, chemically alter medications, and produce carcinogens
Gut-associated lymphoid tissue (GALT)

4. 20.1/2 GI Tract Defenses and Normal Microbiota
2nd most common illnesses in US
Usually result from ingestion of microorganisms or their toxins in food and water: Fecal–oral transmission

5. Tooth and Gum Infections
Dental Caries (Tooth Decay)
1 causative agent: ___________
Bacteria bind to pellicle proteins  Cariogenic plaque
Sucrose fermentation  _________ cavity formation
Starch, mannitol, xylitol, etc. are not used by cariogenic bacteria
Old calcified plaque: Dental Calculus or Tartar
Prevention: fluoride aditives and restricting dietary sucrose

6. Pellicle and plaque formation
Fig 20.12

7. Compare to Fig 20.12

8. Dextran

10. Periodontal Disease
Almost everybody has some sign of periodontal disease by age 45
Ginigivitis: 1st stage. Gum Inflammation. Inflammatory response to the variety of bacteria growing on gums
Gingivitis can progress to Periodontitis
Chronic periodontitis can cause bone destruction and tooth loss in older people

12. Acute necrotizing ulcerative gingivitis (ANUG) – Trench mouth

13. The Stages of Tooth Decay
The Stages of Periodontal Disease
Compare to Fig 20.14

14. 20.3 GI Tract Diseases caused by Nonhelminthic Microorganisms
Food poisoning
Bacterial Acute Diarrhea
S. aureus
B. cereus
Samonella
Shigella
STEC
Other E. coli
Campylobacter
C. diff
Vibrio cholerae
Viral acute diarrhea
Rotavirus
Norovirus
Chronic diarrhea
Giardia

15. Salmonella Currently  10% of chickens infected
Salmonellosis  Salmonella enterica  Gastroenteritis
Most reported of foodborne diseases in US
Typhoid Fever  Salmonella typhi
In humans only (carriers); enteroinvasive  blood; Symptoms last 2–3 weeks, antibiotics
Fig. 10.2

16. Fig. 10.3

17. Other Causative Agents of Acute Diarrhea
Infections have longer incubation periods than intoxication (12 hours to 2 weeks)
Shigella (Bacillary Dysentery)
Toxin
Severe diarrhea or dysentery; 20,000 – 30,000 cases /year in US
STEC  _______________________ Besides diarrhea also hemolytic uremic syndrome (HUS) in  10%.| E.g.: E. coli O157:H7
Other E. coli

18. Campylobacter Gastroenteritis
Most common bacterial cause of diarrhea.
Mostly Campylobacter jejuni
Microaerophilic  special culture conditions Almost all retail chicken contaminated Also in beef Low ID50 (~ 1000) 1 in 1000 cases: Guillain-Barré syndrome

19. Clostridium difficile-Associated Diarrhea
C. difficile growth following antibiotic therapy
Exotoxin production
From mild diarrhea to life threatening colitis
Millions of cases per year
Nosocomial disease, associated with hospitalized patients and nursing home residents

20. Cholera Secretory diarrhea  rice water stool (up to 1L/h)!
ID50 high (108 cells)
Oral (ORS) or i.v. rehydration reduces mortality rate from 70% to < 1%
Adhere to microvilli and secrete enterotoxin

21. Viral Gastroenteritis
Rotavirus
3 million cases annually
Main diarrheal illness of infants and children
1-2 day incubation; 1 week illness
Norovirus
50% of U.S. adults have antibodies
1-2 day incubation; 1-3 day illness
Treated with rehydration

22. Food Poisoning
Infection: caused by growth of a pathogen in intestines.
Incubation times range from 12 hours to 2 weeks. Symptoms generally include fever.
Intoxication: due to ingestion of preformed bacterial toxins.
Symptoms appear 1– 48 hours after ingestion. Usually no fever.
Infections and intoxications cause diarrhea and dysentery (some gastroenteritis)
Usually treated with fluid and electrolyte replacement.

23. Intoxication: Staphylococcal Food Poisoning
Staphylococcus aureus – inoculated into foods during preparation
Heat resistant exotoxin acts as enterotoxin – boiling for 30 mins not sufficient to denature this exotoxin!
Incubation period 1 – 6 hours; rapid recovery
Contaminated meats (ham!), fish, potato salad, custards, etc.
Mode of transmission: Human reservoir (nose); skin abscesses …

24. Events in Staphylococcal Food Poisoning

25. Chronic Diarrhea Giardiasis – caused by Giardia lamblia
Fig 20.9
Giardiasis – caused by Giardia lamblia
Drinking feces contami- nated water (camping, swimming)
Type of traveler’s diarrhea
Symptoms: malaise, nausea, flatulence, weakness, and abdominal cramps that persist for weeks.
Diagnosis is based on identification of the protozoa in the small intestine.
 7% of population healthy carriers. Day care centers

26. Gastritis and Gastric Ulcers
Causative agent:________________________
Inflammatory response to bacteria  Peptic ulcer disease (gastric and duodenal ulcers)
% of people in US infected – only 15% develop ulcers. (Blood type O more susceptible)
Bacteria produces urease (urea  ammonia)  neutralizes stomach acid
Antibiotic treatment is effective

28. Hepatitis Hepatitis A Hepatitis B Hepatitis C Trans-mission
Causative agent
Chronic liver disease?
Vaccine?
Hepatitis A
Fecal-oral
Picornaviridae No
Inactivated virus
Hepatitis B
Parenteral, STD
Hepadnaviridae
Yes
Recombinant/ subunit
Hepatitis C
Parenteral
Filoviridae
Hepatitis D
HBV coinfection
(Subvirus satellite)
Deltaviridae
HBV vaccine
Hepatitis E
Caliciviridae

29. Foodborne 2011 Illnesses Hospitalizations Deaths

30. 20.4 Helminthic GI Tract Diseases

31. 4 Basic Helminth Life and Transmission Cycles

33. Clinical Considerations
Wide variety of helminthic diseases affect humans and animals
Diagnosis :
Differential blood count showing ______________
Serological tests showing abs to helminthic antigens
History of travel to or immigration from tropics
Fecal analysis

34. Enterobius vermicularis = ______________
See Ch. 4
Transmission type?
Diagnosis?

35. Nematodes – Review and Ascariasis
Pinworm most common in US
2nd most common in US: Ascaris lumbricoides up to 30 cm long
Many children (20 – 60%), especially in SE
~85% infections asymptomatic, however “failure to thrive” as in many intestinal parasites
Ingestion of soil transmitted eggs
Cycle through lungs

36. Tapeworm
contracted by consumption of undercooked beef, pork, or fish containing encysted larvae
Scolex attaches to the intestinal mucosa of humans (definitive host)  matures into adult tapeworm
Eggs shed in feces and must be ingested by an intermediate host
Adult tapeworms may be undiagnosed in a human
Diagnosis based on observation of proglottids and eggs in feces.

37. Cysticercosis Taenia solium Taenia saginata
Transmission type?
Human __________ host; Pig or cattle __________ host.

38. The Common Pet Tapeworm: Dipylidium caninum
Tapeworm segment breaks, releasing eggs
Tapeworm segments and flea dirt are found together in Rover’s dog bed.
Rover licks himself and swallows fleas
Eggs eaten by grazing flea larvae
Tapeworm segments break releasing eggs
Flea larvae pupate

39. Dipylidium caninum (dog tapeworm) mainly infects dogs and cats, but is occasionally found in humans.

40. The End