1. Microbial Diseases of the Digestive System

2. Digestive System

3. Digestive System
Gastrointestinal tract – mouth, pharynx, esophagus, stomach, small and large intestine
Accessory structures – teeth, tongue, salivary glands, liver, gallbladder, pancreas

4. Bacterial Population of the GI Tract
Mouth – large microbial population
Stomach – relatively small due to high acid content
Small intestine – small population
Large intestine – VERY large. 100 billion bacteria per gram of feces

5. Bacterial Diseases of the Mouth
Dental caries (tooth decay)
So many bacteria in the mouth that it is difficult to say which bacteria is the most common cause of decay
Streptococcus mutans is one of the more important cariogenic bacteria

6. Development of caries
Bacteria accumulate on the teeth, this is called PLAQUE
The bacteria in the plaque break down sucrose in our diet to produce glucose and fructose
Glucose is converted to dextran, the fructose is metabolized and produces acids that attack the enamel of the tooth
Over time the enamel can be destroyed and the softer tissue inside the tooth is attacked by bacteria causing decay which can lead to tooth loss!

7. Decay Prevention
Removal of the plaque – visit the dentist and dental hygienist
Regular brushing and flossing to remove and reduce the bacterial population of the teeth
Consume less sucrose
If you ignore decay it can lead to tooth loss, gum disease, periodontal disease, and visits to the dentist that you would rather avoid!

8. Dental caries!

9. Cutting Board

10. Bacterial Diseases of the Lower Digestive System
Infections
Pathogen in the GI tract and multiples
Delayed symptoms while bacterial population grows
Fever usually present
Diarrhea
Abdominal cramps, nausea, vomiting
Intoxications
Ingestion of preformed toxin
Rapid onset
Fever usually not present
Diarrhea
Abdominal cramps, nausea, vomiting
Self limiting, feel better within 24 hours usually

11. Staphylococcal food poisoning
Staphylococcus aureus is the cause
Leading cause of gastroenteritis
Ingest the toxin that causes the symptoms of the condition
Food is contaminated during preparation, bacteria incubate in the food and produce the toxin that is heat stable, you ingest the toxin (yummy)
Symptoms usually appear in one to six hours

12. Staphylococcal food poisoning (continued)
Foods at risk are custards, cream pies, ham, and poultry
Foods prepared and not chilled have the potential for this type of food poisoning
Toxin is heat stable so it is usually not destroyed when the food is reheated
It is the toxin the causes the usual symptoms

13. Traveler’s Diarrhea Estimated 25-50% of travelers affected
High risk areas
Latin America
Africa
Middle East
Asia
Causative agent 80% of the time is E. coli
Prevention
Hand washing
Avoid eating food from street vendors
Careful use of purified water

14. Shigella sonnei

15. Shigellosis (Bacillary dysentery)
Bacterial infection caused by members of genus Shigella
Shigella sonnei most common cause in the US
Bacteria multiply in the small intestine releasing a toxin that causes severe diarrhea, fever, vomiting, cramps, mucous in stool
Onset in hours
Acquired through contaminated food or water
Salads, raw vegetables, milk, dairy, meat
Fecal-oral route
Adults can get it from children sick with the disease
Recovery in a few days, antibiotics used in only the most serious cases
Fluid replacement

16. Shigellosis statistics
165,000,000 cases per year - mainly in developing countries
1,000,000 deaths - mostly in children
In the US reported cases are about 18,000 per year

17. Salmonella

18. Salmonellosis
Members of genus Salmonella are found in the GI react of humans and other animals
Almost all are pathogenic
Bacteria multiply in the intestine and can enter the blood and lymphatic system becoming systemic
Fever, nausea, abdominal pain, cramps, diarrhea
Recovery in a few days
Eggs and meats especially poultry are sources of the infection
Pet turtles and iguanas are carriers of Salmonella
“Four inch law” passed in 1975 banning the sale of turtles with a shell of smaller than 4”

19. Typhoid Fever Salmonella typhi
Carried by humans, acquired by poor sanitation
Symptoms are high fever, headache, diarrhea
Death is rare, usually associated with ulceration of the intestinal wall
1-3% of recovered patients become carriers
Typhoid Mary
Still a problem during foreign travel

20. Cholera Vibrio cholerae
Acquired from contaminated water (fresh of salt), and foods from contaminated water
Severe diarrhea from cholera toxin
Rice water stools
Treated by electrolyte replacement

21. Spread of Cholera

22. Helicobacter pylori Robin Warren and Barry Marshall 2005 Nobel prize
Cause of stomach and duodenal ulcers
Stomach cancer?
Fecal-oral transmission?
Treatment with antibiotics usually cures the ulcer
Bacteria lives and survives in the mucous layer of the stomach

23. Mumps Viral infection of the parotid salivary gland
Swelling of the parotid gland, fever, pain when swallowing
Transmitted via saliva and respiratory secretions
MMR vaccine
Mumps in adult males causes swelling of the testes (ouch!)
In RARE cases sterility can result

24. Salivary Glands

25. Hepatitis Inflammation of the liver
Viral hepatitis is the second most reported infectious disease in the US
At least 5 different viruses have been discovered that cause hepatitis
Hepatitis A, B, C, D, and E

26. Hepatitis distribution

27. Hepatitis A Single-stranded RNA virus Oral-fecal transmission
Infection form food common, blood infection is rare
Anorexia, malaise, nausea, diarrhea, fever, chills
Jaundice
Symptoms last 2-21 days
Full recovery is typical
No carrier state
Vaccine available

28. Hepatitis B Enveloped DNA virus Blood products Sexually transmitted
10% of patients become chronic carriers
Liver cancer?
Vaccine is available

29. Hepatitis C Single stranded RNA virus Silent epidemic
Symptoms may take 20 years to appear
100,000 new infections per year
8000 deaths per year
No vaccine
Interferon treatment