Question 1

Which of the following is NOT considered a defense mechanism of the gastrointestinal (GI) tract against infection?

Accepted Answer

Ciliated epithelia

Question 2

A patient presents with severe, watery diarrhea described as 'rice-water stool,' muscle cramps, and signs of dehydration after returning from a region with poor sanitation. Which pathogen is most likely responsible, and what is its primary virulence factor?

Accepted Answer

Vibrio cholerae; cholera toxin that disrupts electrolyte transport

Question 3

Which of the following statements about the normal biota of the gastrointestinal tract is CORRECT?

Accepted Answer

E. coli in the large intestine synthesizes vitamin K for the host.

Question 4

A 7-year-old child presents with pronounced anal itching, especially at night. Microscopic examination of adhesive tape pressed to the perianal region reveals oval eggs. Which organism is most likely responsible, and what is the recommended approach for treatment?

Accepted Answer

Enterobius vermicularis; treat the entire household with antihelminthic drugs

Question 5

Which of the following best explains why antibiotics are generally contraindicated in the treatment of Shiga-toxin-producing E. coli (STEC) infections?

Accepted Answer

Antibiotics may increase toxin release, worsening systemic effects

Question 6

A patient develops severe abdominal cramps, fever, and pseudomembranous colitis after a course of broad-spectrum antibiotics. Which organism is most likely responsible, and what is the first step in management?

Accepted Answer

Clostridium difficile; withdraw the offending antibiotic

Question 7

A 3-year-old child presents with watery diarrhea, vomiting, and dehydration. The child is from a region with poor sanitation and lacks maternal antibodies. Which virus is the most likely cause, and what is the best preventive measure?

Accepted Answer

Rotavirus; immunization with inactivated viral vaccine

Question 8

Which of the following best describes the pathogenesis of Helicobacter pylori in the development of gastric ulcers?

Accepted Answer

Production of urease to neutralize stomach acid, allowing colonization of the mucosa

Question 9

A patient presents with fever, abdominal pain, and bloody diarrhea after eating undercooked beef. Laboratory tests confirm the presence of E. coli O157:H7. Which serious complication should be monitored for, and what is its pathophysiology?

Accepted Answer

Hemolytic uremic syndrome (HUS); Shiga toxin damages endothelial cells leading to hemolytic anemia and kidney failure

Question 10

Which of the following helminths is transmitted via ingestion of undercooked pork containing cysticerci, and what is a potential complication if humans ingest the eggs instead?

Accepted Answer

Taenia solium; cysticercosis with possible neurocysticercosis

Question 11

A patient develops severe nausea and vomiting within 3 hours after eating unrefrigerated cream pastries at a picnic. Several others who ate the same food are also ill. Which organism is most likely responsible, and what property of its toxin explains the rapid onset?

Accepted Answer

Staphylococcus aureus; preformed, heat-stable enterotoxin

Question 12

Which of the following statements about hepatitis B virus (HBV) is TRUE?

Accepted Answer

HBV can be transmitted by needlestick injuries and remains infectious in dried blood for days

Question 13

A patient with AIDS presents with chronic, persistent diarrhea. Which protozoan is most likely responsible, and what property makes it difficult to eradicate from water supplies?

Accepted Answer

Cryptosporidium; oocysts are resistant to chlorine disinfection

Question 14

Which of the following best explains the role of normal gut biota in human health?

Accepted Answer

They help with digestion, synthesize vitamins, and train the immune system to recognize antigens

Question 15

A patient presents with dysentery, abdominal pain, and weight loss after traveling to a tropical region. Stool examination reveals trophozoites with a single nucleus and ingested red blood cells. Which organism is most likely responsible, and what is a key feature of its pathogenesis?

Accepted Answer

Entamoeba histolytica; secretes enzymes that dissolve tissues and cause flask-shaped ulcers

Question 16

Which of the following is a hallmark laboratory finding in helminthic infections and what is its significance?

Accepted Answer

Eosinophilia; increased eosinophils indicate a host response to helminths

Question 17

A patient develops gingivitis with swollen, bleeding gums and deepening pockets between the teeth and gums. Which of the following best describes the pathogenesis of periodontitis?

Accepted Answer

Polymicrobial biofilms and mineralized calculus induce chronic inflammation and tissue destruction

Question 18

Which of the following organisms is associated with the development of vitamin B12 deficiency due to its ability to absorb the vitamin in the human intestine?

Accepted Answer

Diphyllobothrium latum

Question 19

A patient presents with fever, malaise, and jaundice. Laboratory tests reveal elevated liver enzymes and the presence of anti-HAV IgM antibodies. Which of the following is the most likely mode of transmission for this infection?

Accepted Answer

Fecal-oral route via contaminated food or water

Infectious Diseases Affecting the Gastrointestinal Tract: Mini-Textbook Study Notes

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드