Ch 20 Infectious Diseases Affecting the Digestive System

Ch 20 Infectious Diseases Affecting the Digestive System

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.

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)

20. 1/2 GI Tract Defenses and Normal Microbiota • 2 nd most common illnesses in US • Usually result from ingestion of microorganisms or their toxins in food and water: Fecal–oral transmission

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

Pellicle and plaque formation Fig 20. 12

Compare to Fig 20. 12

Dextran

Periodontal Disease Almost everybody has some sign of periodontal disease by age 45 Ginigivitis: Ginigivitis 1 st 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

Acute necrotizing ulcerative gingivitis (ANUG) – Trench mouth

The Stages of Tooth Decay The Stages of Periodontal Disease Compare to Fig 20. 14

20. 3 GI Tract Diseases caused by Nonhelminthic Microorganisms Bacterial Acute Diarrhea • • Samonella Shigella STEC Other E. coli Campylobacter C. diff Vibrio cholerae Food poisoning • S. aureus • B. cereus Viral acute diarrhea • Rotavirus • Norovirus Chronic diarrhea • Giardia

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

Fig. 10. 3

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 O 157: H 7 • Other E. coli

Campylobacter Gastroenteritis Most common bacterial cause of diarrhea. Mostly Campylobacter jejuni Microaerophilic special culture conditions Almost all retail chicken contaminated Also in beef Low ID 50 (~ 1000) 1 in 1000 cases: Guillain-Barré syndrome

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

Cholera • Secretory diarrhea rice water stool (up to 1 L/h)! 8 • ID 50 high (10 cells) • Oral (ORS) or i. v. rehydration reduces mortality rate from 70% to < 1% • Adhere to microvilli and secrete enterotoxin

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

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.

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 …

Events in Staphylococcal Food Poisoning

Chronic Diarrhea Fig 20. 9 • Giardiasis – caused by Giardia lamblia • Drinking feces contaminated 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

Gastritis and Gastric Ulcers Causative agent: ____________ • Inflammatory response to bacteria Peptic ulcer disease (gastric and duodenal ulcers) • 30 - 50 % 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

Hepatitis Transmission 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 Yes No Hepatitis D HBV coinfection (Subvirus satellite) Deltaviridae Yes HBV vaccine Hepatitis E Fecal-oral Caliciviridae No No

2011 Foodborne Illnesses Hospitalizations Deaths http: //www. cdc. gov/foodbornebur den/2011 -foodborneestimates. html

20. 4 Helminthic GI Tract Diseases

4 Basic Helminth Life and Transmission Cycles

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

Enterobius vermicularis = _______ See Ch. 4 Transmission type? Diagnosis?

Nematodes – Review and Ascariasis • Pinworm most common in US • 2 nd 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

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.

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

The Common Pet Tapeworm: Dipylidium caninum T a p e w o r m s e g m e n Tapeworm segments and flea dirt are found together in Rover’s dog bed. t b r e a k s , r e l e a s i n g e g g s Tapeworm segments break releasing eggs Eggs eaten by grazing flea larvae Flea larvae pupate Rover licks himself and swallows fleas

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