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Microbial Diseases of the Digestive System

25. Microbial Diseases of the Digestive System. Escherichia coli Gastroenteritis. Occurs as traveler's diarrhea and epidemic diarrhea in nurseries. 50% of feedlot cattle may have enterohemorrhagic strains in their intestines.

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Microbial Diseases of the Digestive System

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  1. 25 Microbial Diseases of the Digestive System

  2. Escherichia coli Gastroenteritis • Occurs as traveler's diarrhea and epidemic diarrhea in nurseries. • 50% of feedlot cattle may have enterohemorrhagic strains in their intestines. • Enterohemorrhagic strains such as E. coli O157:H7 produce Shiga toxin. • O = cell wall antigen • H = flagellar antigen

  3. Campylobacter Gastroenteritis • Campylobacter jejuni • Usually transmitted in cow's milk

  4. Helicobacter Peptic Ulcer Disease • Treated with antibiotics • H. pylori causes stomach cancer Figure 11.12

  5. Helicobacter Peptic Ulcer Disease Figure 25.14

  6. Yersinia Gastroenteritis • Y. enterocolitica and Y. pseudotuberculosis • Can reproduce at 4°C • Usually transmitted in meat and milk

  7. Clostridium Infections • Clostridium perfringens Gastroenteritis • Grow in intestinal tract, producing exotoxin • Clostridium difficile–associated diarrhea • Grow following antibiotic therapy • Associated with hospitalized patients and nursing home residents

  8. Bacillus cereus Gastroenteritis • Ingestion of bacterial exotoxin produces mild symptoms.

  9. Mumps • Mumps virus • Enters through respiratory tract • Infects parotid glands • Prevented with MMR vaccine Figure 25.15

  10. Hepatitis • Inflammation of the liver. • Hepatitis may result from drug or chemical toxicity, EB virus, CMV, or the hepatitis viruses.

  11. Hepatitis

  12. Hepatitis B Virus Figure 25.16

  13. Viral Gastroenteritis • Rotavirus: • 3 million cases annually • 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 Figure 25.17

  14. Mycotoxins • Mycotoxins are produced by some fungi • Claviceps purpurea • Grows on grains • Produces ergot • Toxin restricts blood flow to limbs; causes hallucination • Aspergillus flavus • Grows on grains • Produces aflatoxin • Toxin causes liver damage; liver cancer

  15. Giardiasis • Giardia lamblia • Transmitted by contaminated water • Diagnosed by microscopic examination of stool for ova and trophozoite • Treated with metronidazole Figure 25.18

  16. Cryptosporidiosis • Cryptosporidium hominis • Transmitted by oocysts in contaminated water • Diagnosed by acid-fast staining of stool or presence of antibodies by FA or ELISA • Treated with oral rehydration Figure 25.19

  17. Cyclospora Diarrheal Infection • Cyclospora cayetanensis • Transmitted by oocysts in contaminated water • Diagnosed by microscopic examination for oocysts • Treated with trimethoprim and sulfamethoxazole

  18. Amoebic Dysentery • Entamoeba histolytica • Amoeba feeds on RBCs and GI tract tissues • Diagnosis by observing trophozoites in feces • Treated with metronidazole Figure 12.18b

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