Question 1

Which of the following is NOT a reason why the skin is an effective barrier against microbial infection?

Accepted Answer

It is constantly moist, preventing microbial colonization.

Question 2

Which enzyme found in sweat and tears hydrolyzes peptidoglycan in bacterial cell walls?

Accepted Answer

Lysozyme

Question 3

A patient presents with a rapidly spreading, bright red rash with peeling skin, primarily around the nose and mouth. The causative agent is a lysogenized strain of Staphylococcus aureus. Which toxin is responsible for this condition?

Accepted Answer

Exfoliative toxin

Question 4

Which of the following statements about Staphylococcus aureus is FALSE?

Accepted Answer

It is coagulase-negative.

Question 5

A child develops a crusted, nonbullous sore on the face that spreads by autoinoculation. Which organism is most likely responsible?

Accepted Answer

Staphylococcus aureus

Question 6

Which of the following is a distinguishing feature of Streptococcus pyogenes compared to Staphylococcus aureus?

Accepted Answer

It grows in chains and is beta-hemolytic.

Question 7

Which hemolytic pattern is associated with Streptococcus pyogenes on blood agar?

Accepted Answer

Beta hemolysis (clear zone)

Question 8

A burn patient develops a blue-green pus in their wound. Which organism is most likely responsible, and what pigment causes this coloration?

Accepted Answer

Pseudomonas aeruginosa; pyocyanin

Question 9

Which of the following is the primary cause of inflammatory (moderate) acne?

Accepted Answer

Propionibacterium acnes

Question 10

A patient presents with a macular rash, Koplik’s spots, and a history of fever and cough. Which virus is the most likely cause?

Accepted Answer

Measles virus (Rubeola)

Question 11

Which of the following is a complication associated with chickenpox (varicella) that is increased by aspirin use?

Accepted Answer

Reye’s syndrome

Question 12

Which of the following fungal genera is most likely to cause tinea pedis (athlete’s foot)?

Accepted Answer

Trichophyton

Question 13

A newborn develops conjunctivitis with a large amount of pus and corneal ulceration after passing through the birth canal. Which organism is most likely responsible?

Accepted Answer

Neisseria gonorrhoeae

Question 14

Which of the following is the leading cause of infectious blindness worldwide?

Accepted Answer

Chlamydia trachomatis (trachoma)

Question 15

A patient presents with a papular rash and intense itching, especially at night. The causative agent is a mite that burrows into the skin. What is the most likely diagnosis?

Accepted Answer

Scabies

Question 16

Which of the following statements about the treatment of cutaneous mycoses is correct?

Accepted Answer

Oral terbinafine is used for tinea unguium (nail infections).

Question 17

Which of the following is a characteristic of Pseudomonas aeruginosa that contributes to its role in nosocomial infections?

Accepted Answer

Ability to form biofilms on medical devices

Question 18

A patient with a history of swimming in a hot tub develops a superficial infection of hair follicles. Which organism is most likely responsible?

Accepted Answer

Pseudomonas aeruginosa

Question 19

Which of the following is a superantigen produced by Streptococcus pyogenes that can lead to necrotizing fasciitis?

Accepted Answer

Exotoxin A

Question 20

A patient presents with a painless, deep ulcer on the skin after traveling to West Africa. Laboratory tests identify a mycobacterium. What is the most likely diagnosis?

Accepted Answer

Buruli ulcer

Microbial Diseases of the Skin and Eyes: Structure, Normal Flora, and Pathogenesis

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