Question 1

Which of the following body sites is considered sterile under healthy conditions?

Accepted Answer

Blood

Question 2

A patient develops severe diarrhea after a course of broad-spectrum antibiotics. Which mechanism best explains why Clostridium difficile is able to cause disease in this scenario?

Accepted Answer

Antibiotics kill normal gut microbiota, allowing C. difficile to outcompete other microbes.

Question 3

Which equation best represents the enzymatic reaction that allows Helicobacter pylori to survive in the acidic environment of the stomach?

Accepted Answer

$$\mathrm{Urea + H_2O \xrightarrow{urease} 2NH_3 + CO_2$}$$

Question 4

Which of the following is NOT a function of the intestinal microbiota?

Accepted Answer

Direct oxygen transport in blood

Question 5

A Gram stain of dental plaque would most likely reveal which of the following?

Accepted Answer

Mostly Gram-positive cocci and rods

Question 6

Which property allows Staphylococcus species to thrive on human skin?

Accepted Answer

Tolerance to dry, salty, and slightly acidic conditions

Question 7

Which of the following best describes the relationship between prebiotics and probiotics?

Accepted Answer

Prebiotics serve as food for probiotics, enhancing their growth and activity.

Question 8

Which genera dominate the two main human gut enterotypes, and how is diet related to their prevalence?

Accepted Answer

Bacteroides and Prevotella; Bacteroides is associated with high protein and animal fat diets, Prevotella with high carbohydrate diets.

Question 9

Which of the following statements about the human microbiome is TRUE?

Accepted Answer

The microbiome is acquired during and after birth from the environment and other people.

Question 10

Why does a high-sugar diet contribute to dental caries?

Accepted Answer

Sugar is fermented by oral bacteria, producing acids that lower pH and dissolve enamel.

Question 11

Which of the following is a plausible reason why women are more susceptible to urinary tract infections (UTIs) than men?

Accepted Answer

Women's urethra is shorter and closer to the anus, facilitating bacterial entry.

Question 12

Which of the following best describes the role of vaginal Lactobacillus in healthy adult women?

Accepted Answer

It produces lactic acid, maintaining a low pH that inhibits pathogens.

Question 13

Which of the following is a basic characteristic of Clostridium difficile that helps it cause disease?

Accepted Answer

It forms endospores resistant to heat and disinfectants.

Question 14

Which of the following is a plausible outcome of dysbiosis in the gut microbiome?

Accepted Answer

Increased susceptibility to infections and inflammation

Question 15

Which equation best represents the acid production by Streptococcus mutans during sugar fermentation, contributing to dental caries?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$ \rightarrow 2CH_3CHOHCOOH}$$

Question 16

Which of the following is a real-world application of a fecal transplant?

Accepted Answer

Treating antibiotic-associated diarrhea caused by Clostridium difficile

Question 17

Which defense mechanism is primarily responsible for keeping the lower respiratory tract microbe-free?

Accepted Answer

Mucociliary escalator and immune cells

Question 18

Which of the following best describes a synbiotic?

Accepted Answer

A mixture of probiotic and prebiotic that beneficially affects the host by altering the microbiome

Question 19

Which of the following is a plausible effect of the virome in the human microbiome?

Accepted Answer

It can influence bacterial populations and host immunity.

Question 20

Which of the following is a common probiotic found in yogurt and other fermented foods?

Accepted Answer

Lactobacillus acidophilus

ch 24

Study Guide - Practice Questions

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