Question 1

Which bacterium is most commonly associated with dental caries due to its ability to ferment sugars and produce lactic acid?

Accepted Answer

Streptococcus mutans

Question 2

A patient presents with severe watery diarrhea after drinking untreated water in a developing country. Laboratory analysis reveals the presence of curved, Gram-negative rods. Which pathogen is most likely responsible?

Accepted Answer

Vibrio cholerae

Question 3

Which of the following best explains why fluoride in toothpaste helps prevent dental caries?

Accepted Answer

It modifies tooth enamel, making it resistant to acid.

Question 4

A patient with a history of antibiotic use develops severe diarrhea and pseudomembranous colitis. Which treatment is most effective for restoring normal intestinal microbiota?

Accepted Answer

Fecal transplant

Question 5

Which of the following is a key virulence factor produced by Enterotoxigenic E. coli (ETEC) that leads to watery diarrhea?

Accepted Answer

Enterotoxin

Question 6

A child develops fever, swelling of the salivary glands, and later, viral meningitis. Which virus is most likely responsible, and how can it be prevented?

Accepted Answer

Mumps virus; live attenuated vaccine

Question 7

Which of the following statements about Shigella infection is correct?

Accepted Answer

It can cause hemolytic uremic syndrome due to Shiga toxin.

Question 8

A patient with chronic hepatitis develops cirrhosis and is at increased risk for liver cancer. Which hepatitis virus is most likely involved if the infection is not curable but can be managed with antivirals?

Accepted Answer

Hepatitis B virus

Question 9

Which of the following best describes the mechanism by which Vibrio cholerae causes dehydration?

Accepted Answer

It produces an enterotoxin that increases secretion of electrolytes, causing water loss by osmosis.

Question 10

A patient presents with jaundice, malaise, and a history of recent travel. Laboratory tests confirm acute hepatitis. Which virus is most likely responsible, and what is the primary route of transmission?

Accepted Answer

Hepatitis A virus; fecal-oral route

Question 11

Which protozoan is responsible for 'beaver fever' and is commonly transmitted through contaminated water?

Accepted Answer

Giardia lamblia

Question 12

Which of the following is a distinguishing feature of viral gastroenteritis caused by rotavirus or norovirus?

Accepted Answer

It is self-limiting and often resolves within a week.

Question 13

A patient develops severe bloody diarrhea and kidney dysfunction after eating undercooked beef. Which E. coli strain is most likely responsible?

Accepted Answer

Enterohemorrhagic E. coli (EHEC)

Question 14

Which of the following best explains why Clostridium difficile infections are often associated with hospitals?

Accepted Answer

Antibiotic use disrupts normal microbiota, allowing C. difficile to colonize.

Question 15

Which of the following is the most effective method for preventing transmission of hepatitis B virus?

Accepted Answer

Subunit vaccine

Question 16

A patient with a history of intravenous drug use is diagnosed with chronic hepatitis, which is curable with a combination of interferon and antivirals. Which virus is most likely responsible?

Accepted Answer

Hepatitis C virus

Question 17

Which of the following statements about mumps is correct?

Accepted Answer

It can cause sterility in males due to testicular swelling.

Question 18

Which of the following best describes the pathogenesis of Helicobacter pylori in gastritis?

Accepted Answer

It produces ammonia to neutralize stomach acid and degrades the mucous lining.

Question 19

Which of the following protozoan pathogens is resistant to chlorine disinfectant and must be removed from water using ozone or UV treatment?

Accepted Answer

Cryptosporidium

Question 20

A patient develops fever, abdominal pain, and diarrhea after eating eggs contaminated with animal feces. Which pathogen is most likely responsible, and why are antibiotics not always recommended?

Accepted Answer

Non-typhoidal Salmonella; antibiotics can prolong carriage and increase resistance

Digestive System Infections: Microbiology Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards