Staphylococcal Infections MCQ Quiz | Infectious Diseases – Bacterial

1. Which virulence factor of *Staphylococcus aureus* binds to the Fc portion of IgG, thereby inhibiting opsonization and phagocytosis?

2. A patient presents with high fever, hypotension, a diffuse erythematous rash, and multi-organ failure. This presentation is most strongly associated with which staphylococcal toxin?

3. The mechanism of methicillin resistance in MRSA is primarily due to:

4. A 25-year-old male with a history of intravenous drug use presents with fever, chills, and a new-onset heart murmur. Blood cultures grow Gram-positive cocci in clusters. The most likely causative organism for his infective endocarditis is:

5. Staphylococcal Scalded Skin Syndrome (SSSS) in newborns is caused by the systemic effects of which toxin?

6. Which of the following is a key laboratory test used to differentiate *Staphylococcus aureus* from coagulase-negative staphylococci (CoNS)?

7. A patient develops vomiting and diarrhea 2-4 hours after eating potato salad at a picnic. The symptoms resolve within 24 hours. This type of food poisoning is most likely caused by:

8. The *mecA* gene, responsible for methicillin resistance, is carried on which mobile genetic element?

9. Panton-Valentine Leukocidin (PVL), a cytotoxin often associated with community-acquired MRSA (CA-MRSA), primarily targets which cells?

10. What is the first-line treatment for a severe, systemic infection confirmed to be caused by Methicillin-Susceptible *Staphylococcus aureus* (MSSA)?

11. A patient with a prosthetic heart valve develops endocarditis 3 months post-surgery. The most common causative agent for this condition is:

12. Which of the following skin infections is characterized by superficial, honey-crusted lesions, commonly seen in children, and can be caused by *S. aureus*?

13. The catalase test is performed on a Gram-positive coccus isolate. The test is positive (bubbles produced). This result effectively rules out which of the following genera?

14. A young, sexually active female presents with a urinary tract infection. The urine culture grows a coagulase-negative *Staphylococcus* that is resistant to novobiocin. The most likely organism is:

15. The primary reservoir for *Staphylococcus aureus* in humans, from which most infections originate, is the:

16. Which of the following antibiotics is a glycopeptide, often used as the empirical treatment for suspected severe MRSA infections?

17. A carbuncle is best described as:

18. The “slide coagulase test” detects which specific virulence factor of *S. aureus*?

19. For a patient with a severe MRSA pneumonia, which antibiotic is sometimes preferred over vancomycin due to its better lung tissue penetration and inhibition of toxin production?

20. Which feature is characteristic of community-acquired MRSA (CA-MRSA) strains compared to hospital-acquired MRSA (HA-MRSA) strains?

21. A patient is diagnosed with osteomyelitis of the vertebra. Which organism is the most common cause of this condition?

22. The “D-test” is used in the laboratory to detect inducible resistance to which antibiotic in staphylococci that appear erythromycin-resistant and clindamycin-susceptible?

23. Bullous impetigo, characterized by large, flaccid bullae, is a localized form of Staphylococcal Scalded Skin Syndrome caused by the action of:

24. In treating bacteremia caused by MSSA, which of the following is considered inferior to beta-lactam therapy despite in-vitro susceptibility?

25. The ability of *Staphylococcus epidermidis* to cause infections related to catheters and prosthetic devices is primarily due to its ability to: