Question 1

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

Accepted Answer

The skin is resistant to drying and has high salt concentrations, making it inhospitable to many microbes.

Question 2

A patient presents with a rapidly spreading, painful infection of the dermal layer of the skin, often preceded by strep throat. Which organism is most likely responsible, and what is the recommended treatment?

Accepted Answer

Streptococcus pyogenes; treated with beta-lactam antibiotics

Question 3

Which of the following is a correct match between a skin lesion and its description?

Accepted Answer

Vesicle – small fluid-filled lesion

Question 4

Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to beta-lactam antibiotics due to which mechanism?

Accepted Answer

Production of an altered penicillin-binding protein

Question 5

Which virulence factor allows Staphylococcus aureus to evade host immune defenses by blocking chemotaxis and surviving in phagosomes?

Accepted Answer

Coagulase

Question 6

A burn patient develops a blue-green pus at the wound site. Which organism is most likely responsible, and what pigment is associated with this infection?

Accepted Answer

Pseudomonas aeruginosa; pyocyanin

Question 7

Which of the following best explains why cold sores caused by HSV-1 tend to recur in the same location?

Accepted Answer

The virus remains latent in the trigeminal nerve ganglion and reactivates along the same nerve pathway.

Question 8

Which of the following is a cutaneous mycosis, and what is its causative agent?

Accepted Answer

Tinea pedis; dermatophytes

Question 9

A child presents with isolated pustules that become crusted and is diagnosed with impetigo. Which toxin is most likely involved if the infection is caused by Staphylococcus aureus?

Accepted Answer

Exfoliative toxin A

Question 10

Which of the following best describes the relationship between chickenpox and shingles?

Accepted Answer

Chickenpox is the primary infection, and shingles is a reactivation of the same virus (varicella-zoster) later in life.

Question 11

Which of the following is a common cause of conjunctivitis (pink eye)?

Accepted Answer

Haemophilus influenzae

Question 12

A newborn develops ophthalmia neonatorum. Which organism is most likely responsible, and what is the standard preventive measure?

Accepted Answer

Neisseria gonorrhoeae; administration of antibiotics to the eyes after birth

Question 13

Which of the following statements about measles is correct?

Accepted Answer

Measles disables the immune system, making secondary infections a major cause of death.

Question 14

Which of the following best describes the pathogenesis of acne?

Accepted Answer

Propionibacterium acnes produces fatty acids that stimulate an immune response after pores are clogged by sebum and dead skin cells.

Question 15

Which of the following is a characteristic of Pseudomonas aeruginosa that contributes to its persistence in hospital environments?

Accepted Answer

Ability to form biofilms and resistance to many antibiotics and disinfectants

Question 16

A patient with cystic fibrosis develops a chronic lung infection with a blue-green pigment in sputum. Which organism is most likely responsible, and what is the pigment?

Accepted Answer

Pseudomonas aeruginosa; pyocyanin

Question 17

Which of the following is the only available treatment for fungal keratitis caused by Fusarium spp.?

Accepted Answer

Natamycin

Question 18

Scabies is caused by which organism, and what is a common symptom?

Accepted Answer

Sarcoptes scabiei; itching due to mites burrowing under the skin

Question 19

Which of the following best explains why herd immunity is important for measles control?

Accepted Answer

Measles has no other animal host, so high vaccination rates can lead to eradication.

Microbial Diseases of the Skin and Eyes: Structure, Pathogenesis, and Clinical Manifestations

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