Microbial Diseases of the Digestive System

Digestive System

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

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

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

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!

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!

Dental caries!

Cutting Board

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

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

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

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

Shigella sonnei

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 12-50 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

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

Salmonella

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”

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

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

Spread of Cholera

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

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

Salivary Glands

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

Hepatitis distribution

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

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

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