Chapter 25: Microbial Diseases of the Digestive Sytem

Question 1

Give examples and location of the normal microbiota of the digestive system

Answer 1

a. Millions of bacteria per ml of saliva
b. Large numbers in large intestine
c. 100 billion bacteria per gram of feces
d. Mouth- Streptococcus salivarus (tongue), S. mitis (cheeks), S. sanguis (teeth), and Bacteroides, Fusarium and spirochetes in the teeth and gums
e. Stomach and small intestines- few microorganisms due to the HCl and fast movement
f. Large intestine- Lactobacillus, Bacteroides, E. coli, Enterobacter, Klebsiella, Proteus, they assist in degradation of food and production of vitamins
g. Feces- 40% is microbial cell material

Question 2

List the etiologic agent for the different forms of hepatitis.

Answer 2

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 Yes None

Hepatitis D Pareteral, HBV coinfection Deltaviridae Yes HBV vaccine

Hepatitis E Fecal-oral Caliciviridae No HAV vaccine
table

Question 3

Mode of transmission and etiologic agent of amoebic and bacillary dysentery

Answer 3

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

Amoebic Dysentery:

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

Question 4

List diseases transmitted by poultry products

Answer 4

a. Salmonellosis- Salmonella gastroenteritis- symptoms include nausea, abdominal pain, diarrhea. can lead to septicemia
b. Campylobacter gastroenteritis- symptoms include fever, cramping, abdominal pain and diarrhea

Question 5

Characteristics of Gairdiasis

Answer 5

a. Caused by Giardia lamblia-
i. Protozoa that grows in the intestine of humans and wild animals and is transmitted in contaminated water.
ii. Symptoms of giardiasis are malaise, nausea, flatulence, weakness, and abdominal cramps that persist for weeks.
iii. Diagnosis is based on identification of the protozoa in the small intestine.

Question 6

Describe staphylococcal food poisoning.

Answer 6

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

Question 7

Most common cause of travelers diarrhea

Answer 7

Escherichia coli

Question 8

Give the modes of transmission of 
Trichinella
Vibrio
Giardia
Clostriduim perfringens
Staphylococcus aureus

Answer 8

i. Trichinella – ingestion of contaminated pork
ii. Vibrio – ingestion of contaminated oysters, crustaceans
iii. Giardia – ingestion of contaminated water
iv. Clostridium perfringens – ingestion of contaminated canned goods
v. Staphylococcus aureus – ingestion of contaminated ham, custard, and cream pies

Question 9

List the characteristics of cholera

Answer 9

Pathogen Vibrio cholerae O:1 and O:139- associated with brackish waters, estuaries, oyster beds

Symptoms Diarrhea with large water loss, “rice water stools”

Intoxication/Infection Cholera toxin (exotoxin)

Diagnosis Isolation of bacteria

Treatment Rehydration; doxycycline

Question 10

treatment for gastrointestinal infections

Answer 10

fluid and electrolyte replacement

Question 11

Give examples of gram negative rods that cause gastroenteritis

Answer 11

Shigella, Salmonella, E. coli, and Yersinia among others.