Question 1

Which of the following best describes the relationship between the human body and its normal microbiota?

Accepted Answer

Bacterial cells outnumber human cells in the body, and many of these bacteria form mutualistic relationships with their host.

Question 2

Which of the following is an example of mutualism in the human body?

Accepted Answer

Bacteria in the human colon synthesizing vitamin K while receiving nutrients and shelter.

Question 3

Which site on the human body is most densely populated by anaerobic bacteria such as Bacteroides and Lactobacillus?

Accepted Answer

Intestines

Question 4

Which of the following best describes the rhizosphere?

Accepted Answer

The narrow region of soil influenced by root secretions and associated with a dense microbial community.

Question 5

Which of the following is a plausible consequence of a baby being delivered by Caesarian section rather than vaginal birth?

Accepted Answer

The baby’s gut microbiota will be more similar to environmental microbes, increasing the risk of certain autoimmune diseases.

Question 6

Which of the following is NOT a way that normal microbiota can become opportunistic pathogens?

Accepted Answer

Stable, unchanging host environment

Question 7

Which of the following best describes the difference between incidence and prevalence in epidemiology?

Accepted Answer

Incidence is the number of new cases during a specific period, while prevalence is the total number of cases at a given time.

Question 8

A fungus secretes an antibiotic that inhibits the growth of nearby bacteria, but the fungus is neither harmed nor helped by the bacteria. What type of symbiotic relationship is this?

Accepted Answer

Amensalism

Question 9

Which of the following is a real-world example of zoonosis?

Accepted Answer

Rabies virus transmitted from bats to humans via bites

Question 10

Which of the following is a correct statement about the transmission of infectious diseases?

Accepted Answer

Vehicle transmission involves inanimate objects such as food, water, or air.

Question 11

Which of the following best describes the function of bacterial virulence factors such as coagulase and hyaluronidase?

Accepted Answer

They help bacteria evade the immune system and invade host tissues.

Question 12

Which of the following is an example of a sign of disease, rather than a symptom?

Accepted Answer

Fever

Question 13

Which of the following best describes the role of Bifidobacterium longum infantis in breast-fed infants?

Accepted Answer

It utilizes complex carbohydrates in breast milk, promoting gut health and protecting against necrotizing enterocolitis.

Question 14

Which of the following is the correct sequence of events in the establishment of an infectious disease?

Accepted Answer

Contamination → Infection → Disease

Question 15

Which of the following best explains why an acute disease with a high mortality rate is unlikely to cause a pandemic?

Accepted Answer

High mortality prevents widespread transmission because infected individuals die before spreading the disease widely.

Question 16

Which of the following is a characteristic of an endemic disease?

Accepted Answer

It is constantly present in a population, often at a low level.

Question 17

Which of the following best describes the difference between exotoxins and endotoxins?

Accepted Answer

Exotoxins are proteins secreted by bacteria, while endotoxins are part of the Gram-negative bacterial cell wall.

Question 18

Which of the following is a plausible outcome if a person is exposed to a dose of Mycobacterium tuberculosis lower than the infectious dose (ID)?

Accepted Answer

The person is unlikely to develop disease because the number of bacteria is insufficient to establish infection.

Question 19

Which of the following is an example of a nonliving reservoir of infection?

Accepted Answer

Soil contaminated with Clostridium spores

Question 20

Which of the following best describes herd immunity?

Accepted Answer

Immunity in most of a population, reducing the likelihood of disease spread.

Normal Flora, Symbiosis, and Infectious Disease: Microbiome and Epidemiology

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