$\text{Virulence} \propto \frac{1}{\text{ID}}$

$\text{Number of microbes} \rightarrow \text{Signs and symptoms}$

Question 1

Which of the following is NOT a site with normal resident flora in the human body?

Accepted Answer

Liver

Question 2

Why is knowledge of resident flora important to a clinical microbiologist?

Accepted Answer

It helps distinguish between normal flora and pathogens in clinical samples.

Question 3

Which of the following best describes microbial antagonism?

Accepted Answer

The ability of normal flora to prevent overgrowth of harmful microbes

Question 4

A patient develops an infection after normal flora is introduced to a previously sterile site. This is known as:

Accepted Answer

Endogenous infection

Question 5

Which of the following is a true pathogen?

Accepted Answer

Influenza virus

Question 6

What is the minimum number of microbes required for infection to proceed called?

Accepted Answer

Infectious dose (ID)

Question 7

Which of the following equations correctly represents the relationship between infectious dose and virulence?

Accepted Answer

$	ext{Virulence} \propto \frac{1}{	ext{ID}}$

Question 8

Which adhesion mechanism is used by Neisseria gonorrhoeae to attach to host cells?

Accepted Answer

Fimbriae

Question 9

A patient is infected with a microbe that produces hyaluronidase. What is the likely effect of this enzyme?

Accepted Answer

It breaks down connective tissue, facilitating invasion.

Question 10

Which of the following is a characteristic of a chronic carrier?

Accepted Answer

They shed the infectious agent for a long period without symptoms.

Question 11

Which stage of infection is characterized by vague feelings of discomfort and nonspecific complaints?

Accepted Answer

Prodromal stage

Question 12

Which of the following is a sign, not a symptom, of infectious disease?

Accepted Answer

Fever

Question 13

Which portal of exit is most likely for pathogens causing respiratory infections?

Accepted Answer

Respiratory – mucus, sputum, nasal drainage, saliva

Question 14

Which of the following is an example of a zoonosis?

Accepted Answer

Influenza transmitted from chickens to humans

Question 15

Which equation best represents the relationship between the number of microbes and the progression of disease?

Accepted Answer

$	ext{Number of microbes} ightarrow 	ext{Signs and symptoms}$

Question 16

Which of the following is a mechanical vector?

Accepted Answer

Housefly carrying bacteria on its legs

Question 17

Which of the following is a major factor that weakens host defenses and increases susceptibility to infection?

Accepted Answer

Chemotherapy/immunosuppressive drugs

Question 18

Which of the following best describes the difference between a reservoir and a source?

Accepted Answer

A reservoir is the primary habitat of a pathogen; a source is where infection is actually acquired.

Question 19

Which of the following is a characteristic of exotoxins?

Accepted Answer

They are secreted by living bacterial cells and are highly specific in their action.

Question 20

Which of the following is a universal precaution recommended by the CDC to prevent healthcare-associated infections?

Accepted Answer

Treat all patient specimens as potentially infectious.

Mechanisms of Pathogenicity: Microbial Interactions with the Host

Study Guide - Practice Questions