Question 1

Which of the following best describes the relationship between humans and their normal microbiota?

Accepted Answer

The microbiota has a mutualistic relationship, providing benefits such as vitamin production, immune system maturation, and competition with pathogens.

Question 2

A patient develops severe diarrhea after a course of antibiotics. Which bacterial species is most likely responsible for this condition?

Accepted Answer

Clostridioides difficile

Question 3

Why can Group B Streptococcus (GBS) be harmless in adult women but cause severe disease in newborns?

Accepted Answer

Newborns have reduced immunity and lack established normal microbiota to compete with GBS.

Question 4

What is the term for pathogens that cause disease when the host's immune system is weakened or normal microbiota is disrupted?

Accepted Answer

Opportunistic pathogens

Question 5

A pathogen with a high $$ID_{50}$$ value is best described as:

Accepted Answer

Less infectious, requiring many cells to cause infection in 50% of hosts.

Question 6

Which of the following statements about endotoxins and exotoxins is correct?

Accepted Answer

Exotoxins are made of protein and can be released by both Gram-positive and Gram-negative bacteria.

Question 7

The basic reproduction number ($$R_0) of a $$pathogen is defined as:

Accepted Answer

The number of people a single infected person is expected to infect in a fully susceptible population.

Question 8

Which region of lipopolysaccharide (LPS) is considered the endotoxin in Gram-negative bacteria?

Accepted Answer

Lipid A

Question 9

Superantigens are dangerous because they:

Accepted Answer

Overstimulate the immune system, causing massive inflammation.

Question 10

Which exotoxin family do AB toxins belong to, and what are the functions of the 'A' and 'B' components?

Accepted Answer

Type III; 'B' binds to the cell receptor, 'A' exerts effects inside the cell.

Question 11

A pathogen enters the body through a surgical incision. This is an example of which portal of entry?

Accepted Answer

Parenteral entry

Question 12

Which of the following is NOT a possible outcome if a fetus is infected in utero with a TORCH pathogen?

Accepted Answer

Increased resistance to infection

Question 13

What is the main function of adhesins in microbial pathogenesis?

Accepted Answer

To allow pathogens to stick to host cells

Question 14

Which of the following is a mechanism by which bacteria can evade the host immune system?

Accepted Answer

Antigen masking, antigen mimicry, and antigen variation

Question 15

A bacterium is able to survive in the host by snatching iron from transferrin. Which virulence factor is responsible for this?

Accepted Answer

Siderophores

Question 16

Which of the following is NOT a portal of exit for pathogens?

Accepted Answer

Skin hair

Question 17

A hospital worker is handling Ebola virus. Which biosafety level (BSL) is required?

Accepted Answer

BSL-4

Question 18

Which of the following is a standard precaution that healthcare workers must follow?

Accepted Answer

Hand hygiene

Question 19

A patient with tuberculosis requires which transmission precaution?

Accepted Answer

Airborne precautions

Question 20

A scientist is comparing the toxicity of two bacterial toxins. Toxin A has an $$LD_{50} of 1 mg$$, and Toxin B has an $$LD_{50} of 100 mg. $$Which toxin is more potent, and why?

Accepted Answer

Toxin A is more potent because a lower dose is required to kill 50% of hosts.

Chapter 10: Host-Microbe Interactions and Pathogenesis – Step-by-Step Study Guidance

Study Guide - Practice Questions

Study Guide - Flashcards