1. Microbial Diseases of the Digestive System
Chapter 25
Microbial Diseases of the Digestive System

2. Q&A
The United States frequently imports cheese and wine from France. In return, the United States exports horses to France. What does this have to do with the disease of trichinellosis?

3. The Digestive System Learning Objective
25-1 Name the structures of the digestive system that contact food.

4. The Human Digestive System
Figure 25.1

5. Normal Microbiota of the Digestive System
Learning Objective
25-2 Identify parts of the gastrointestinal tract that normally have microbiota.

6. Normal Microbiota Millions of bacteria per ml of saliva
Large numbers in large intestine
100 billion bacteria per gram of feces

7. Defenses
Stomach: Acidic
Small intestine: Paneth cells

8. There have been instances in which a surgeon was using spark producing instruments to remove intestinal polyps and a small explosion occurred. What ignited? 25-1
How are normal microbiota confined to the mouth and large intestine? 25-2

9. Bacterial Diseases of the Mouth
Learning Objective
25-3 Describe the events that lead to dental caries and periodontal disease.

10. A Healthy Human Tooth
Figure 25.2

11. Dental Caries (Tooth Decay)
Figure 25.3a

12. Dental Caries (Tooth Decay)
Figure 25.3b

13. The Stages of Tooth Decay
Figure 25.4

14. The Stages of Periodontal Disease
Figure 25.5

15. Bacterial Diseases of the Mouth
Pathogen
Dental caries
Streptococcus mutans
Periodontal disease
Porphyromonas spp.
Acute necrotizing gingivitis
Prevotella intermedia

16. Diseases in Focus: Bacterial Diseases of the Mouth
Can you identify infections that could cause persistent sore, swollen, red, or bleeding gums, as well as tooth pain or sensitivity and bad breath?

17. Why are “sugarless” candies and gum, which actually contain sugar alcohols, not considered cariogenic (causing caries)? 25-3

18. Diseases of Lower Digestive System
Learning Objective
25-4 List the causative agents, suspect foods, signs and symptoms, and treatments for staphylococcal food poisoning, shigellosis, salmonellosis, typhoid fever, cholera, gastroenteritis, and peptic ulcer disease.

19. Diseases of Lower Digestive System
Infection: Growth of a pathogen
Incubation is from 12 hours to 2 weeks
Fever
Intoxication: Ingestion of toxin
Symptoms appear 1 to 48 hours after ingestion
Gastroenteritis: Diarrhea, dysentery
Treatment: Oral rehydration therapy

20. Staphylococcal Food Poisoning
Pathogen
Staphylococcus aureus
Symptoms
Nausea, vomiting, and diarrhea
Intoxication/Infection
Intoxication
Enterotoxin (superantigen)
Diagnosis
Phage typing
Treatment
None

21. Events in Staphylococcal Food Poisoning
Figure 25.6

22. Shigellosis (Bacillary Dysentery)
Pathogen
Shigella spp.
Symptoms
Tissue damage and dysentery
Intoxication/Infection
Infection
Endotoxin and Shiga exotoxin
Diagnosis
Isolation of bacteria
Treatment
Quinolones

23. Invasion of Intestinal Wall by Shigella
Figure 25.7

24. Shigellosis
Figure 25.8

25. Salmonellosis and Typhoid Fever
Figure 25.10

26. Typhoid Fever Caused by Salmonella typhi
Bacteria spread throughout body in phagocytes
1–3% of recovered patients become chronic carriers

27. Disease
Salmonellosis
Typhoid Fever
Pathogen
Salmonella enterica
S. typhi
Symptoms
Nausea and diarrhea
High fever, significant mortality
Intoxication/ Infection
Infection
Endotoxin
Diagnosis
Isolation of bacteria; serotyping
Treatment
Oral rehydration
Quinolones; cephalosporins

28. Salmonellosis
Figure 25.9

29. Determine the Salmonella Source
Food
Exposed
Not Exposed
Ill (a)
Not ill (b)
Ill (c)
Not ill (d)
Chicken salad 47 40 6 13
Cole slaw 32 20 21 33
Fruit salad 34 30 19 23
Potato salad 42 39 11 14
Tomato salad 24 29

30. Determine the Salmonella Source
Food
Relative Risk
Chicken salad
1.71
Cole slaw
1.58
Fruit salad
1.17
Potato salad
1.18
Tomato salad
3.86

31. Vibrios Cholera Noncholera vibrios
Vibrio cholerae serotypes that produce cholera toxin
Toxin causes host cells to secrete Cl–, HCO–, and water
Noncholera vibrios
Usually from contaminated crustaceans or mollusks
V. cholerae serotypes other than O:1, O:139, eltor
V. parahaemolyticus
V. vulnificus

32. Vibrio cholerae
Figure 25.11

33. Vibrio cholerae O:1 and O:139 V. vulnificus
Disease
Cholera
Noncholera vibrios
Pathogen
Vibrio cholerae O:1 and O:139
V. parahaemolyticus
V. vulnificus
Symptoms
Diarrhea with large water loss
Cholera-like diarrhea, but generally milder
Rapidly spreading tissue destruction
Intoxication/Infection
Cholera toxin (exotoxin)
Infection, enterotoxin
Infection, siderophores
Diagnosis
Isolation of bacteria
Treatment
Rehydration; doxycycline
Rehydration; antibiotics
Antibiotics

34. Escherichia coli Gastroenteritis
Pathogenic E. coli
Attach to intestinal cells with fimbriae
Produce toxins
May aggregate

35. Escherichia coli Gastroenteritis
Disease
Traveler’s Diarrhea
STEC
Pathogen
Enterotoxigenic, enteroinvasive, enteraggregative E. coli
Shiga-toxin-producing E. coli
Symptoms
Watery diarrhea
Shigella-like dysentery; hemorrhagic colitis and hemolytic uremic syndrome

36. Escherichia coli Gastroenteritis
Disease
Traveler’s Diarrhea
STEC
Intoxication/Infection
Infection
Endotoxin
Infection Shiga exotoxin
Diagnosis
Isolation of bacteria
Treatment
Oral rehydration
Quinolones; cephalosporins

37. Campylobacter Gastroenteritis
Pathogen
Campylobacter jejuni
Symptoms
Fever, abdominal pain, diarrhea
Intoxication/Infection
Infection
Diagnosis
Isolate bacteria
Reservoir
Chickens, cow’s milk

38. Helicobacter Peptic Ulcer Disease
Figure 25.13

39. Helicobacter Peptic Ulcer Disease
Pathogen
Helicobacter pylori
Symptoms
Peptic ulcers
Intoxication/Infection
Infection
Diagnosis
Urea breath, bacterial culture
Treatment
Antimicrobial drugs

40. Yersinia Gastroenteritis
Pathogen
Y. enterocolitica, Y. pseudotuberculosis
Symptoms
Abdominal pain and diarrhea, usually mild; may be confused with appendicitis
Intoxication/Infection
Infection
Endotoxin
Diagnosis
Bacterial culture; serotyping
Transmitted
Meat, milk

41. Clostridium and Bacillus Gastroenteritis
Pathogen
C. perfringens
C. difficile
B. cereus
Symptoms
Diarrhea
Diarrhea to colitis
Nausea and vomiting; diarrhea
Intoxication/Infection
Infection
Exotoxin
Intoxication
Diagnosis
Isolation of bacteria
Cytotoxin assay

42. Clostridium and Bacillus Gastroenteritis
Pathogen
C. perfringens
C. difficile
B. cereus
Transmitted
Metronidazole;
discontinue other antibiotic therapy
Source of Infection
Meats
Elimination of normal microbiota
Rice dishes

43. Salmonellosis and typhoid fever are caused by closely related organisms. Why was typhoid fever almost entirely eliminated in developed countries by modern sewage treatment whereas salmonellosis has not been? 25-4

44. Diseases in Focus: Bacterial Diseases of the Lower Digestive System
An 8-year-old boy had diarrhea, chills, fever (39.3º C), abdominal cramps, and vomiting for 3 days. The next month, his 12-year-old brother experienced the same symptoms. Two weeks before the first patient became ill, the family had purchased a small (10 cm) red-eared slider turtle at a flea market.
Can you identify infections that could cause these symptoms?

45. Viral Diseases of the Digestive System
Learning Objectives
25-5 List the causative agents, modes of transmission, sites of infection, and symptoms for mumps.
25-6 Differentiate hepatitis A, hepatitis B, hepatitis C, hepatitis D, and hepatitis E.
25-7 List the causative agents, mode of transmission, and symptoms of viral gastroenteritis.

46. Viral Diseases of the Digestive System
Mumps
Viral Gastroenteritis
Pathogen
Mumps virus
Rotavirus
Norovirus
Symptoms
Swollen parotid glands
Vomiting, diarrhea, 1 wk
Vomiting, diarrhea, 2–3 days
Incubation
16–18 days
1–3 days
14–48 hr
Diagnosis
EIA
PCR
Treatment
Preventive vaccine
Oral rehydration

47. A Case of Mumps
Figure 25.14

48. Hepatitis An inflammation of the liver
May result from drug or chemical toxicity, EB virus, CMV, or the hepatitis viruses

49. Hepatitis Viruses Disease Transmission Pathogen Chronic Liver Disease?
Vaccine?
Hepatitis A
Fecal-oral
Picornaviridae No
Inactivated virus
Hepatitis B
Parenteral, STI
Hepadnaviridae
Yes
Recombinant
Hepatitis C
Parenteral
Filoviridae
None
Hepatitis D
Pareteral, HBV coinfection
Deltaviridae
HBV vaccine
Hepatitis E
Caliciviridae
HAV vaccine

50. Hepatitis B Virus (HBV)
Figure 25.15

51. Applications of Microbiology: A Safe Blood Supply
Nucleic acid testing (NAT) is used to test donated blood and plasma:
HCV
HIV
West Nile virus
Virus-inactivation is used on plasma

52. Diseases in Focus: Viral Hepatitis
After eating at one restaurant, 355 people were diagnosed with the same hepatitis virus.
Can you identify infections that could cause these symptoms?

53. Diseases in Focus: Viral Diseases of the Digestive System
An outbreak of diarrhea began in mid-June, peaked in mid-August, and tapered off in September. A clinical case was defined as diarrhea (three loose stools during a 24-hour period).
Can you identify infections that could cause these symptoms?

54. Why is mumps included with the diseases of the digestive system? 25-5
Of the several hepatitis diseases, HAV, HBV, HCV, HDV, and HEV, which two now have effective vaccines to prevent them? 25-6
Two very common causes of viral gastroenteritis are caused by rotaviruses and noroviruses. Which of these now can be prevented by a vaccine? 25-7

55. Fungal Diseases of the Digestive System
Learning Objective
25-8 Identify the causes of ergot poisoning and aflatoxin poisoning.

56. Mycotoxin Intoxications
Disease
Ergot Poisoning
Aflatoxin Poisoning
Pathogen
Claviceps purpurea
Aspergillus flavus
Symptoms
Reduced blood to limbs
Liver cirrhosis; liver cancer
Intoxication/
Infection
Mycotoxin in grain
Mycotoxin in food
Diagnosis
Sclerotia in food
Immunoassay for toxin in food
Treatment
None

57. What is the connection between the occasional hallucinogenic symptoms produced by ergot poisoning and a modern illicit drug? 25-8

58. Protozoan Diseases of the Digestive System
Learning Objective
25-9 List the causative agents, modes of transmission, symptoms, and treatments for giardiasis, cryptosporidiosis, Cyclospora diarrheal infection, and amoebic dysentery. 

59. Giardia lamblia
Figure 25.17

60. Giardiasis Pathogen Giardia lamblia Symptoms
Protozoan adheres to intestinal wall, diarrhea
Reservoir
Water or mammals
Diagnosis
FA test
Treatment
Metronidazole; quinacrine

61. Cryptosporidium hominis
Figure 25.18

62. Cryptosporidium hominis in the U. S.
Clinical Focus, p. 355

63. Cryptosporidiosis Pathogen Cryptosporidium hominis Symptoms
Self-limiting diarrhea; may be life-threatening in immunosuppressed people
Reservoir
Cattle; water
Diagnosis
Acid-fast stain; FA; ELISA
Treatment
Oral rehydration

64. Cyclospora Diarrheal Infection
Pathogen
Cyclospora cayetanensis
Symptoms
Watery diarrhea
Reservoir
Humans; birds
Diagnosis
Microscopy
Treatment
Trimethoprim and sulfamethoxazole

65. Entamoeba histolytica
Figures 12.17b, 25.19

66. Amoebic Dysentery Pathogen Entamoeba histolytica Symptoms
Abscesses; significant mortality rate
Reservoir
Humans
Diagnosis
Microscopy; serology
Treatment
Metronidazole

67. Is giardiasis caused by ingestion of a cyst or an oocyst? 25-9

68. Helminthic Diseases of Digestive System
Learning Objective
25-10 List the causative agents, modes of transmission, symptoms, and treatments for tapeworms, hydatid disease, pinworms, hookworms, ascariasis, and trichinellosis.

69. Worldwide Prevalence of Helminthic Diseases
Figure 25.20

70. Tapeworms
Figure 12.26

71. Ophthalmic Cysticercosis
Figure 25.21

72. Echinococcus granulosus
Figure 12.27

73. Hydatid Disease
Figure 25.22

74. Tapeworms and Hydatid Disease
Pathogen
Taenia saginata
T. solium
Diphyllobothrium latum
Echinococcus granulosus
Symptoms
Neurocysticercosis
Tissue damage
Intermediate Host
Cattle, pigs, fish
Humans
Definitive Host
Dogs

75. Tapeworms and Hydatid Disease
Diagnosis
Microscopic exam of feces
Praziquantel; albendazole
Treatment
Serology; X-ray exam
Surgical removal; albendazole

76. Pinworms
Figure 12.28

77. Pinworms Pathogen Enterobius vermicularis Symptoms Itching around anus
Intermediate host
Humans
Definitive host
Diagnosis
Microscopy
Treatment
Pyrantel pamoate

78. Hookworms
Figure 25.23

79. Ascariasis lumbricoides
Figure 25.24

80. Heartworm
Figure 12.29

81. Life Cycle of Trichinella spiralis
Figure 25.25

82. Roundworms Disease Hookworms Ascariasis Trichinellosis Pathogen
Necator americanus,
Ancyclostoma duodenale
Ascaris lumbricoides
Trichinella spiralis
Symptoms
Anemia
Few
Intermediate Host
Larva in soil
Human
Mammals
Definitive Host

83. Roundworms Disease Hookworms Ascariasis Trichinellosis Diagnosis
Microscopy
Biopsy; ELISA
Treatment
Mebendazole
Mebendazole; corticosteroids

84. Q&A
The United States frequently imports cheese and wine from France. In return, the United States exports horses to France. What does this have to do with the disease of trichinellosis?

85. What species of tapeworm is the cause of cysticercosis? 25-10

86. Diseases in Focus: Fungal, Protozoan, and Helminthic Diseases
Public health officials in Pennsylvania were notified of cases of watery diarrhea with frequent, sometimes explosive, bowel movements among persons associated with a residential facility. The disease was associated with eating snow peas.
Can you identify infections that could cause these symptoms?