Question 1

Which protein is the main component of keratinocytes in the epidermis, and what is its primary function?

Accepted Answer

Keratin; provides waterproofing and strength

Question 2

Which layer of the skin contains blood vessels, nerves, hair follicles, sweat gland ducts, and sebaceous glands?

Accepted Answer

Dermis

Question 3

What enzyme found in perspiration breaks down bacterial cell walls, and what is its target substrate?

Accepted Answer

Lysozyme; breaks down peptidoglycan

Question 4

Which virus is responsible for chickenpox, and how is it most commonly transmitted?

Accepted Answer

Varicella zoster virus; respiratory droplets

Question 5

A patient presents with a painful, vesicular rash on the lips. Which virus is most likely responsible, and where does it become latent?

Accepted Answer

HSV-1; trigeminal nerve

Question 6

Why are the MMR and Varicella vaccines not administered to infants until they are at least one year old?

Accepted Answer

The vaccines contain live attenuated viruses and should not be given before the immune system develops

Question 7

Which bacterium is a major cause of acne, and what fermentation product does it produce?

Accepted Answer

Propionibacterium acnes; propionic acid

Question 8

What two factors protect Staphylococcus aureus from phagocytosis?

Accepted Answer

Capsule formation and coagulase production

Question 9

Which selective and differential medium is used to identify Staphylococcus aureus based on its ability to ferment mannitol?

Accepted Answer

Mannitol salt agar

Question 10

A patient with a burn develops a bluish-green pus in the wound. Which bacterium is most likely responsible, and what pigment does it produce?

Accepted Answer

Pseudomonas aeruginosa; pyocyanin

Question 11

Which two biochemical tests can differentiate Staphylococcus aureus from Streptococcus pyogenes?

Accepted Answer

Catalase and coagulase tests

Question 12

What is the function of the hyaluronic acid capsule in Streptococcus pyogenes?

Accepted Answer

Camouflages the bacteria from the host immune system

Question 13

Which bacterium is the etiological agent of gas gangrene, and what is a characteristic feature of this infection?

Accepted Answer

Clostridium perfringens; foul-smelling gas production

Question 14

Which three genera of fungi are responsible for most tinea (dermatophyte) infections?

Accepted Answer

Trichophyton, Microsporum, Epidermophyton

Question 15

A patient presents with a skin ulcer after being bitten by a sand fly in a tropical region. Which protozoan is most likely responsible?

Accepted Answer

Leishmania species

Question 16

Which two protective factors are found in tears, and what is the function of lactoferrin?

Accepted Answer

Lysozyme and lactoferrin; lactoferrin binds free iron

Question 17

What is the leading cause of preventable microbial blindness worldwide, and what is the etiological agent?

Accepted Answer

Trachoma; Chlamydia trachomatis

Question 18

A contact lens wearer develops severe corneal inflammation. Which protozoan is most likely responsible for this keratitis?

Accepted Answer

Acanthamoeba

Question 19

How is helminthic keratitis (river blindness) introduced into humans, and which eye structures are primarily damaged?

Accepted Answer

By blackfly bite; damages optic nerve and cornea

Question 20

Which equation best represents the catalase reaction used to differentiate Staphylococcus aureus from Streptococcus pyogenes?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Microbiology Study Guide: Skin and Eye Infections (Chapter 17)

Study Guide - Practice Questions