6. Diarrheal Diseases Cont'd and Other

  1. Escherichia coli
    most strains are commensal, but some can cause diarrhea
  2. E. coli associated with diarrhea

    nonhuman reservoir - STEC (EHEC)

    use toxins - ETEC, STEC (EHEC), EAggEC
  3. E. coli diagnosis
    • serotyping
    • bioassays - for detection of toxin, tissue culture, invasion assay
    • genetic probes and PCR
    • detection of EHEC/STEC
  4. salmonella diseases
    • non-typhoidal salmonellosis or enterocolitis
    • - aymstomatic infection is most common
    • - prevention - proper food handling and storage, cooking food thoroughly, hand washing

    • Typhoid fever (enteric fever)
    • 1-3% of people will carry and shed organisms for over a year after resolution of symptoms
    • preventable with vaccines- also proper sanitation, food handling and washing hands
  5. salmonella transmission and diagnosis
    • person to person via fecal-oral route
    • from animal reservoir (enterocolitis only)
    • diagnosis through culture of stool or blood
  6. salmonella invasive pathogenesis
    • enter though the M cells
    • survive and replicate inside macrophages
    • enter lymph nodes, lymphatics and blood stream
  7. Giardia lamblia
    • reservoir - intestines of humans and other animals
    • transmission - person to person by fecal-oral route
    • causes giardiasis (beaver fever)
    • most common protozoan causing diarrhea
    • cysts are infective stage
  8. hepatitis A virus (HAV)
    • reservoir - humans
    • transmission - fecal-oral
    • diagnosis - detection of IgM specific antibodies
  9. HAV pathogenesis
    • traffics to liver, infects hepatocytes
    • does not cause cytotoxicity - immune mediated
    • antibody response that confers lifelong protection
  10. HAV prevention
    • hygiene
    • sanitation
    • vaccine - reduced incidence in US
    • immune globulin
  11. ascariasis
    • caused by helminth ascaris lumbricoides
    • most common helminth infection - 1/4 of world's population is infected
    • eggs can survive many years in environment
    • transmission is fecal-oral
    • reservoir is humans and pigs
    • diagnosis by ova in stool
  12. Acarsis lumbricoides lifecycle
    • adult worms made in intestine
    • produces fertilized eggs, shed in feces
    • eggs develop into infective embryo
    • ingested by humans, hatch and invade intestine
    • carried to lungs, migrate to throat and swallowed
    • develop in intestine
  13. ascariasis clinical
    • can be asymptomatic for a long time
    • depend on intensity of infection and location - pulmonary, nutritional deficiency, obstruction of small intestine
    • worms can migrate
  14. ascariasis treatment and prevention
    • treatment - antihelminthics
    • prevention - poverty alleviation, hygiene, sanitation, sewage systems, education and health awareness, mass treatment
  15. current issues related to foodborne illnesses
    • emerging and re-emerging foodborne pathogens
    • changing epidemiology of foodborne diseases
    • reasons for emergence and increase in incidence of foodborne diseases
    • drug-resistant infections due to food
  16. classification of foodborne diseases
    • toxin-mediated (without infection)
    • chemical poisoning
    • infection
  17. infection vs. intoxication
    • infection - disease caused my microorganism establishing infection in human host
    • longer incubation period

    • intoxication - disease caused by ingestion of toxin
    • microorganism multiplies in food and produces toxin, not in human host
    • short incubation period
  18. prion diseases
    neurodegenerative disease due to accumulation of abnormal protease-resistant protein in the neurons
  19. changing epidemiology of foodborne diseases
    • new or previously unrecognized pathogens
    • new vehicles and reservoirs of infection
  20. reasons for emergence and increase in incidence of foodborne diseases
    • industrialization and technology - mass distribution and production
    • globalization
    • antibiotics in animal feed
    • change in types of animal feed
  21. solutions to increase in incidence of foodborne diseases
    • stopping use of antibiotics in food
    • feed animals naturally
    • smaller, localized production of food
    • stricter government oversight
Card Set
6. Diarrheal Diseases Cont'd and Other
public health microbiology midterm 2 lecture 6