Question 1

Which of the following is NOT a typical function of the human microbiome?

Accepted Answer

Colonizing the blood and nervous system under normal conditions

Question 2

A newborn delivered via C-section is likely to have a different initial microbiome compared to a vaginally delivered newborn because:

Accepted Answer

C-section babies are exposed primarily to skin and hospital-associated microbes

Question 3

Which of the following statements about the skin microbiome is TRUE?

Accepted Answer

It is dominated by Gram-positive cocci such as coagulase-negative Staphylococcus

Question 4

Why are most skin surfaces and mucus membranes colonized by microflora, but the blood and nervous system are not?

Accepted Answer

Blood and nervous system are protected by physical and immune barriers that prevent colonization

Question 5

Which of the following is a plausible consequence of antibiotic-induced dysbiosis in the gastrointestinal tract?

Accepted Answer

Dominance of antibiotic-resistant species and risk of pseudomembranous colitis

Question 6

A patient develops diarrhea after antibiotic treatment. Which pathogen is most commonly associated with this scenario due to disruption of normal flora?

Accepted Answer

Clostridioides difficile

Question 7

Which of the following factors does NOT directly influence the composition of an individual's microbiome?

Accepted Answer

Blood type

Question 8

Which of the following is a correct description of a virulence factor?

Accepted Answer

A molecule that increases a pathogen's ability to cause disease

Question 9

A bacterium produces hyaluronidase. What is the likely effect of this enzyme?

Accepted Answer

Degradation of hyaluronic acid in the extracellular matrix, aiding tissue invasion

Question 10

Which of the following best explains why iron (Fe) is a limiting factor for bacterial growth in the human body?

Accepted Answer

Human proteins such as transferrin and lactoferrin tightly bind iron, restricting its availability to bacteria

Question 11

Which of the following is an example of a pathogen using a surface appendage for adherence to host cells?

Accepted Answer

Expression of fimbriae (Type I) on the cell surface

Question 12

A patient presents with lockjaw and muscle spasms after a deep wound. Which toxin is most likely responsible?

Accepted Answer

Tetanus toxin

Question 13

Which of the following best describes the action of cholera toxin?

Accepted Answer

Induces fluid release in the small intestine, leading to diarrhea

Question 14

Which equation best represents the ratio of bacterial cells to human eukaryotic cells in the body?

Accepted Answer

$$\frac{10$$^{14}$$}{10$$^{13}$$}$$

Question 15

Which of the following is a plausible effect of probiotics?

Accepted Answer

They are live microbes that can beneficially alter the host microbiome

Question 16

Which of the following is a correct match between a pathogen and its associated disease?

Accepted Answer

Streptococcus pyogenes – impetigo

Question 17

Which of the following mechanisms is used by bacteria to acquire new virulence factors?

Accepted Answer

Horizontal gene transfer via plasmids and pathogenicity islands

Question 18

Which of the following is a correct description of an endotoxin?

Accepted Answer

A lipopolysaccharide component of the outer membrane of Gram-negative bacteria that causes fever and inflammation

Question 19

Which of the following is a plausible reason why the upper respiratory tract is colonized by microflora, but the lower respiratory tract is generally not?

Accepted Answer

The lower respiratory tract is cleared by ciliated epithelium and alveolar macrophages

Question 20

Which of the following best describes the role of lysozyme in the eyes?

Accepted Answer

It degrades peptidoglycan in bacterial cell walls, providing antimicrobial protection

Test 3 (lecture 2) Human Microbiome: Structure, Function, and Influencing Factors

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