Question 1

Which of the following best describes the term 'holobiont' as it relates to the human body?

Accepted Answer

A human plus all of its resident microbiota

Question 2

Which of the following is an example of an endogenous infection?

Accepted Answer

Streptococcus pneumoniae causing pneumonia in an AIDS patient

Question 3

According to the Human Microbiome Project, which of the following statements is TRUE?

Accepted Answer

Healthy humans can harbor potentially dangerous pathogens in low numbers

Question 4

Which of the following sites is now thought to harbor at least some normal microbiota or their DNA, contrary to previous beliefs?

Accepted Answer

Placenta

Question 5

A patient is infected with a microbe that requires only 10 cells to cause disease, while another microbe requires 10,000 cells. Which statement is correct regarding their virulence?

Accepted Answer

The microbe with an infectious dose of 10 cells is more virulent

Question 6

Which of the following is NOT a typical portal of entry for infectious agents?

Accepted Answer

Bone marrow

Question 7

A bacterium produces hyaluronidase, an enzyme that breaks down host tissues. This enzyme is best classified as:

Accepted Answer

An exoenzyme

Question 8

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

Accepted Answer

Exotoxins are secreted by living bacteria, while endotoxins are part of the outer membrane of gram-negative bacteria

Question 9

A patient presents with fever, swollen lymph nodes, and leukocytosis. Which of the following best describes these findings?

Accepted Answer

Signs of infection

Question 10

Which of the following is an example of a biological vector in the transmission of infectious disease?

Accepted Answer

A mosquito transmitting malaria

Question 11

A disease that is highly communicable, especially through direct contact, is best described as:

Accepted Answer

Contagious

Question 12

Which of the following best illustrates vertical transmission of a pathogen?

Accepted Answer

Transmission of HIV from mother to child via breast milk

Question 13

A patient is infected with a pathogen that manipulates host cell gene expression without altering the DNA sequence. This is an example of:

Accepted Answer

Epigenetic modification

Question 14

During which stage of infection does a pathogen exhibit its greatest virulence and multiply at high levels?

Accepted Answer

Acute phase

Question 15

Which of the following is a plausible reason why a patient with AIDS is more susceptible to opportunistic infections?

Accepted Answer

Their immune defenses are compromised, allowing normal biota to cause disease

Question 16

A researcher is investigating a new disease outbreak. According to Koch’s postulates, which of the following steps is essential to establish causation?

Accepted Answer

Isolate the suspected pathogen and demonstrate it causes disease in a healthy host

Question 17

Which of the following best describes the difference between a sign and a symptom of disease?

Accepted Answer

A sign is objective evidence observed by others; a symptom is subjective and felt by the patient

Question 18

A patient is infected with a pathogen that enters through the respiratory tract, attaches to host cells, evades phagocytosis, and produces exotoxins. Which of the following best describes the sequence of events?

Accepted Answer

Portal of entry → adhesion → surviving host defenses → causing disease

Question 19

Which of the following is a plausible real-world example of a polymicrobial infection?

Accepted Answer

A patient with influenza who subsequently develops bacterial pneumonia

Question 20

Which of the following equations best represents the relationship between infectious dose (ID) and virulence?

Accepted Answer

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

The Human Host and Its Microbiome: Infection, Disease, and Pathogenesis

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