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Chapter 25, part A

This chapter explores microbial diseases of the digestive system, including how they are transmitted through food and water, the role of normal microbiota, and specific bacterial infections. It covers topics such as dental caries, periodontal disease, and bacterial diseases of the lower digestive system. The symptoms, treatment, and prevention of these diseases are discussed.

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Chapter 25, part A

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  1. Chapter 25, part A Microbial Diseases of the Digestive System

  2. Microbial Diseases of the Digestive System • Transmitted in food and water • Fecal-oral cycle can be broken by: • Proper sewage disposal • Disinfection of drinking water • Proper food preparation and storage

  3. The Digestive System Figure 25.1

  4. Normal Microbiota • >300 species in mouth • Large numbers in large intestine, including: • Bacteroides • E. coli • Enterobacter • Klebsiella • Lactobacillus • Proteus

  5. Bacterial Infections: Mouth - Dental Caries Figure 25.3a, b

  6. Tooth Decay Sucrose Fructose + Glucose Glucose Dextran (plaque) protects organism Fructose Energy and Lactic acid Acid breaks down tooth enamel http://www.mchoralhealth.org/OpenWide/media/flash/flashsniff_decay.htm http://www.mchoralhealth.org/OpenWide/mod1_1.htm Figure 25.4

  7. Periodontal Disease Figure 25.5

  8. Babies and caries • Bottles and caries • Lactose - glucose and galactose • Poor feeding practices without appropriate preventive measures can lead to a distinctive pattern of caries in susceptible infants and toddlers commonly known as baby bottle tooth decay (BBTD), a form of severe early childhood caries (ECC). Frequent bottle feeding at night, and extended and repetitive use of a no-spill training cup are associated with ECC.

  9. Bacterial Diseases of the Lower Digestive System • Symptoms usually include diarrhea, gastroenteritis, dysentery • Treated with fluid and electrolyte replacement • Infection caused by growth of pathogen • Incubation from 12 hr to 2 wk • Intoxication caused by ingestion of toxin • Symptoms appear 1-48 hr after ingestion

  10. Staphylococcal Food Poisoning • Staphylococcus aureus enterotoxin is a superantigen Figure 25.6

  11. Shigellosis • Shigella spp. producing Shiga toxin • Shiga toxin causes inflammation and bleeding Figure 25.8

  12. Salmonellosis • Salmonella enterica serovars such as S. enterica Typhimurium • Mortality (<1%) due to septic shock caused by endotoxin Figure 25.9

  13. Salmonellosis and Typhoid Fever Incidence Figure 25.10

  14. Typhoid Fever • Salmonella typhi • Bacteria spread throughout body in phagocytes • 1-3% recovered patients become carriers, harboring Salmonella in their gallbladder

  15. Cholera • Vibrio cholerae serotypes that produce cholera toxin • Toxin causes host cells to secrete Cl–, HCO–, and water Figure 25.12

  16. Noncholera Vibrios • Usually from contaminated crustaceans or mollusks • V. cholerae serotypes other than O:1, O:139, and eltor • V. parahaemolyticus • V. vulnificus

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