Q: Which equation best represents the attack rate in an epidemic investigation?

$$\frac{\text{Number of new cases}}{\text{Total population at risk}} \times 100$$

Question 1

Which of the following best describes microbial antagonism (competitive exclusion) by normal flora?

Accepted Answer

Normal flora compete with pathogens for nutrients and attachment sites, and may produce antimicrobial substances.

Question 2

A patient develops a Clostridioides difficile infection after taking broad-spectrum antibiotics. This is an example of:

Accepted Answer

A superinfection due to disturbance of normal flora.

Question 3

Which of the following is NOT a type of symbiotic relationship described in microbiology?

Accepted Answer

Antagonism

Question 4

John Snow’s investigation of the cholera outbreak in London is significant because it demonstrated:

Accepted Answer

The use of epidemiological mapping to identify sources of infection.

Question 5

Which of the following is an example of indirect contact transmission?

Accepted Answer

A person touches a doorknob contaminated with pathogens and then touches their face.

Question 6

A hospital patient develops pneumonia after being intubated. This infection is best classified as:

Accepted Answer

A health care-associated infection (nosocomial)

Question 7

Which of the following is a biological vector for disease transmission?

Accepted Answer

A mosquito transmitting West Nile virus after ingesting infected blood

Question 8

Which equation best represents the attack rate in an epidemic investigation?

Accepted Answer

$$\frac{	ext{Number of new cases}}{	ext{Total population at risk}} 	imes 100$$

Question 9

Which of the following best describes an opportunistic pathogen?

Accepted Answer

A microbe that causes disease only when the host’s defenses are compromised.

Question 10

Which of the following is NOT a reservoir for infectious disease?

Accepted Answer

Antibiotic

Question 11

A patient contracts Lyme disease after being bitten by a tick. This is an example of:

Accepted Answer

Vector transmission by a biological vector

Question 12

Which of the following scenarios best illustrates mutualism?

Accepted Answer

E. coli in the human gut synthesizes vitamin K for the host and receives nutrients in return.

Question 13

Which of the following is a key reason why hand washing reduces the incidence of puerperal fever in hospitals?

Accepted Answer

It removes transient microbes that may be pathogenic.

Question 14

Which of the following is the best definition of etiology in the context of infectious disease?

Accepted Answer

The study of the cause of a disease.

Question 15

A sneeze can transmit pathogens to people within a certain distance. According to current consensus, what is the maximum distance droplets can travel to cause transmission?

Accepted Answer

$$6\ 	ext{feet}$$

Question 16

Which of the following is an example of vehicle transmission?

Accepted Answer

A person contracts hepatitis B from a contaminated needle.

Question 17

Which of the following best explains why probiotics can help prevent pathogenic colonization after antibiotic treatment?

Accepted Answer

Probiotics restore normal flora, which compete with pathogens for nutrients and attachment sites.

Question 18

Which of the following is a plausible consequence of disturbing normal flora?

Accepted Answer

Colonization and overgrowth of pathogenic microbes.

Question 19

Which of the following is the best example of commensalism?

Accepted Answer

Staphylococcus epidermidis living on human skin without harming or benefiting the host.

Question 20

A nurse accidentally brings a microbe from feces to a patient’s meal by not washing hands. This is an example of:

Accepted Answer

Mechanical vector transmission

Principles of Disease and Epidemiology ~ Chp 14

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