Question 1

Which of the following best explains why the skin is generally resistant to microbial colonization?

Accepted Answer

The skin secretes fatty acids and lysozyme, creating an inhospitable environment for many microbes.

Question 2

A patient presents with a localized, pus-filled lesion surrounded by inflamed tissue on his arm. Gram stain reveals Gram-positive cocci in clusters, and the isolate is coagulase-positive. What is the most likely causative agent?

Accepted Answer

Staphylococcus aureus

Question 3

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

Accepted Answer

It is beta-hemolytic and produces streptolysin and streptokinase.

Question 4

A burn patient develops a blue-green wound infection. The causative organism is a Gram-negative rod that grows in biofilms and is resistant to many antibiotics. Which virulence factor is responsible for the blue-green pigment?

Accepted Answer

Pyocyanin

Question 5

Which of the following best describes the pathogenesis of scalded skin syndrome caused by Staphylococcus aureus?

Accepted Answer

Exfoliative toxins cause separation of skin layers, resulting in widespread blistering.

Question 6

A child presents with crusted pustules around the mouth. The infection is highly contagious and spreads by direct contact. Which organism is most likely responsible?

Accepted Answer

Staphylococcus aureus

Question 7

Which of the following is the primary reason why MRSA (Methicillin-resistant Staphylococcus aureus) is resistant to methicillin?

Accepted Answer

Production of a modified penicillin-binding protein that does not bind methicillin

Question 8

Which of the following skin lesions is defined as a small, fluid-filled lesion?

Accepted Answer

Vesicle

Question 9

A patient with cystic fibrosis develops a chronic lung infection with a Gram-negative rod that forms biofilms and produces a blue-green pigment. Which antibiotic property is most important for treating this infection?

Accepted Answer

Ability to penetrate biofilms and resist inactivation by beta-lactamases

Question 10

Which of the following statements about chickenpox and shingles is correct?

Accepted Answer

Chickenpox is an acute infection, while shingles is a reactivation of latent virus.

Question 11

Which of the following best explains why measles can be eradicated through vaccination?

Accepted Answer

The virus infects only humans and herd immunity can be achieved at 95% vaccination coverage.

Question 12

A patient presents with a rapidly spreading, necrotic skin infection after a minor injury. The causative agent is beta-hemolytic and produces exotoxin A. What is the most likely diagnosis?

Accepted Answer

Necrotizing fasciitis caused by Streptococcus pyogenes

Question 13

Which of the following organisms is most commonly associated with acne and what is its Gram reaction?

Accepted Answer

Propionibacterium acnes; Gram-positive rod

Question 14

A newborn develops pus formation and corneal ulceration shortly after birth. Which organism is most likely responsible, and what is the recommended prevention?

Accepted Answer

Neisseria gonorrhoeae; treat with antibiotics after birth

Question 15

Which of the following best describes the pathogenesis of tinea pedis (athlete's foot)?

Accepted Answer

Fungal growth on keratinized tissue of the feet

Question 16

A patient presents with conjunctivitis (pink eye). Which of the following is NOT a likely cause?

Accepted Answer

Streptococcus pyogenes

Question 17

Which of the following is a key difference between impetigo and erysipelas?

Accepted Answer

Impetigo is a superficial infection, while erysipelas involves the dermal layer and is often preceded by strep throat.

Question 18

Which of the following best describes the mechanism of action for vancomycin resistance in Staphylococcus aureus (VRSA)?

Accepted Answer

Modification of the target molecule for vancomycin

Question 19

A patient with a history of cold sores develops a new lesion after sunburn. Which statement best explains the recurrence?

Accepted Answer

Herpes simplex virus 1 reactivates from latency in the trigeminal nerve ganglion due to stress or UV exposure.

Question 20

Which of the following is the most effective way to prevent trachoma in endemic regions?

Accepted Answer

Improved sanitation and antibiotic therapy

Microbial Diseases of the Skin and Eyes – Study Notes

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