PowerPoint PresentationInfectious
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)
• 2nd 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)
• 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
Fig 20.12
Dextran
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
Periodontal Disease
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
infected
foodborne diseases in US
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)
– 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
Also in beef
Low ID50 (~ 1000)
Most common bacterial
cause of diarrhea.
– Exotoxin production
–Millions of cases per year
–Nosocomial disease, associated with hospitalized patients and nursing home residents
Cholera • Secretory diarrhea
• ID50 high (108 cells)
• Oral (ORS) or i.v. rehydration reduces mortality rate from 70% to < 1%
• Adhere to microvilli and secrete enterotoxin
Viral Gastroenteritis
– 1-2 day incubation; 1 week illness
• Norovirus
• Treated with rehydration
• 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.
• Usually treated with fluid and electrolyte replacement.
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
• 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
Fig 20.9
• 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 D
HBV coinfection
Hepatitis
http://www.cdc.gov/foodborneburd
en/2011-foodborne-estimates.html
Illnesses
Hospitalizations
Deaths
4 Basic Helminth Life and Transmission Cycles
Wide variety of helminthic diseases
affect humans and animals
antigens
– Fecal analysis
Clinical Considerations
Transmission type?
• 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
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.
Taenia solium
Taenia saginata
Cysticercosis
Transmission type?
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
Flea larvae pupate
dogs and cats, but is occasionally found in humans.