Question 1

Which of the following best explains why the stomach and small intestine have fewer microorganisms compared to the large intestine?

Accepted Answer

The acidic pH and rapid movement of contents in the stomach and small intestine limit microbial colonization.

Question 2

Which of the following bacteria is primarily responsible for dental caries, and what is its main mechanism of causing tooth decay?

Accepted Answer

Streptococcus mutans; produces dextran from glucose and lactic acid from fructose, leading to enamel erosion.

Question 3

A patient presents with nausea, vomiting, and diarrhea 4 hours after eating cream pies at a picnic. No fever is present. Which pathogen is most likely responsible, and what is the mechanism?

Accepted Answer

Staphylococcus aureus; intoxication by preformed enterotoxin.

Question 4

Which of the following is the most effective way to break the fecal–oral cycle of transmission for digestive system diseases?

Accepted Answer

Proper disposal of sewage, disinfection of drinking water, and safe food preparation.

Question 5

Which of the following statements about bacterial gastroenteritis is CORRECT?

Accepted Answer

Bacterial infections have a longer incubation period and often present with fever.

Question 6

A patient develops severe watery diarrhea described as 'rice water stools' after drinking water from an estuary. Which pathogen is most likely responsible, and what is the primary treatment?

Accepted Answer

Vibrio cholerae; rehydration therapy and doxycycline.

Question 7

Which of the following is NOT a characteristic of the normal microbiota of the large intestine?

Accepted Answer

Contains primarily Streptococcus mutans.

Question 8

Which of the following diseases is most commonly associated with the ingestion of contaminated poultry products?

Accepted Answer

Salmonellosis and Campylobacter gastroenteritis.

Question 9

Which of the following statements about hepatitis viruses is TRUE?

Accepted Answer

Hepatitis C virus is transmitted parenterally and can lead to chronic infection.

Question 10

Which of the following protozoan diseases is diagnosed by identifying the pathogen in stool samples and is treated with metronidazole?

Accepted Answer

Giardiasis.

Question 11

A patient presents with tissue damage and dysentery. Laboratory results show the presence of Shiga exotoxin. What is the most likely diagnosis and recommended treatment?

Accepted Answer

Shigellosis (Bacillary dysentery); quinolones.

Question 12

Which of the following is a fungal disease of the digestive system caused by a mycotoxin that restricts blood flow to limbs?

Accepted Answer

Ergot poisoning by Claviceps purpurea.

Question 13

Which of the following helminthic diseases is contracted by ingestion of undercooked pork and can result in neurocysticercosis?

Accepted Answer

Taenia solium (pork tapeworm) infection.

Question 14

Which of the following best describes the difference between a gastrointestinal infection and intoxication?

Accepted Answer

Infection has a longer incubation period and often presents with fever; intoxication has a shorter incubation and usually lacks fever.

Question 15

Which of the following is the most common cause of traveler's diarrhea?

Accepted Answer

Escherichia coli.

Question 16

A patient presents with peptic ulcers. Which bacterium is most likely responsible, and what is the recommended treatment?

Accepted Answer

Helicobacter pylori; antibiotics.

Question 17

Which of the following is a characteristic symptom of cholera, and what is the main danger associated with this disease?

Accepted Answer

Rice water stools; severe dehydration due to large water loss.

Question 18

Which of the following is a common mode of transmission for Giardia intestinalis?

Accepted Answer

Ingestion of contaminated water.

Question 19

Which of the following is the primary treatment for most gastrointestinal infections, regardless of the causative agent?

Accepted Answer

Fluid and electrolyte replacement.

Microbial Diseases of the Digestive System – Study Guide

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