Question 1

Which of the following best explains why Staphylococcus aureus is able to evade phagocytosis by the immune system?

Accepted Answer

It expresses Protein A, which binds the Fc region of IgG, inhibiting opsonization.

Question 2

A 25-year-old IV drug user presents with fever, malaise, and a new heart murmur. Blood cultures grow Gram-positive cocci in clusters. Which valve is most likely affected and what is the most likely organism?

Accepted Answer

Tricuspid valve; Staphylococcus aureus

Question 3

Which toxin produced by Staphylococcus aureus is responsible for the rapid onset of vomiting and diarrhea after ingestion of contaminated food?

Accepted Answer

Enterotoxins A-E

Question 4

A patient develops a fever, hypotension, and a diffuse rash that desquamates, especially on the palms and soles, after nasal packing for epistaxis. Which mechanism best explains the pathogenesis of this syndrome?

Accepted Answer

Superantigen-mediated nonspecific activation of T-cells and cytokine storm

Question 5

Which of the following is the drug of choice for treating methicillin-resistant Staphylococcus aureus (MRSA) infections?

Accepted Answer

Vancomycin

Question 6

Staphylococcus aureus is most commonly associated with which of the following bone infections?

Accepted Answer

Osteomyelitis

Question 7

A child presents with diffuse erythematous papules and bullae, followed by widespread epidermal peeling. Which Staphylococcus aureus virulence factor is most likely responsible?

Accepted Answer

Exfoliative toxin

Question 8

Which laboratory test result would help distinguish Staphylococcus aureus from Streptococcus pyogenes?

Accepted Answer

Catalase positive

Question 9

A patient with cystic fibrosis develops pneumonia with patchy infiltrates and salmon-colored sputum after a recent influenza infection. Which organism is most likely responsible?

Accepted Answer

Staphylococcus aureus

Question 10

Which of the following best describes the mechanism of resistance in MRSA?

Accepted Answer

Alteration of penicillin-binding protein

Question 11

A foodborne outbreak of vomiting and diarrhea occurs 3 hours after a picnic. Which property of the responsible toxin explains the rapid onset?

Accepted Answer

It is preformed and heat stable

Question 12

Which of the following is NOT a typical reservoir or mode of transmission for Staphylococcus aureus?

Accepted Answer

Insect vector

Question 13

A patient presents with a hot, tender, red swelling on the skin. Which Staphylococcus aureus virulence factor is most directly responsible for the formation of localized abscesses?

Accepted Answer

Coagulase

Question 14

Which of the following best explains why vancomycin is used to treat MRSA infections?

Accepted Answer

MRSA alters its penicillin-binding protein, making beta-lactams ineffective

Question 15

Which of the following best describes the hemolytic pattern of Staphylococcus aureus on blood agar?

Accepted Answer

Beta-hemolytic

Question 16

A patient with a surgical wound develops fever and cellulitis. Which combination of Staphylococcus aureus virulence factors is most likely involved?

Accepted Answer

Coagulase, exfoliative toxin, TSST-1

Question 17

Which of the following best describes the appearance of Staphylococcus aureus colonies on mannitol salt agar?

Accepted Answer

Small, yellow colonies that ferment mannitol

Question 18

A patient with chronic granulomatous disease is at increased risk for which of the following infections?

Accepted Answer

Staphylococcus aureus

Question 19

Which of the following best explains the pathogenesis of Panton-Valentine leukocidin (PVL) in Staphylococcus aureus infections?

Accepted Answer

It forms pores in infected cells, leading to cell lysis

Question 20

A patient with a history of multiple hospitalizations develops a Staphylococcus aureus infection that is resistant to vancomycin. Which antibiotic is most appropriate for treatment?

Accepted Answer

Quinupristin/dalfopristin

Staphylococcus aureus: Clinical Features, Pathogenesis, and Treatment

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