FRCS Surgical Microbiology & Immunology 2

Question 1

What is the molecular mechanism of MRSA resistance to beta-lactam antibiotics?

Accepted Answer

Expression of an altered penicillin-binding protein (PBP2a) encoded by mecA

Answer

MRSA resistance is conferred by the mecA gene encoding PBP2a, an altered penicillin-binding protein with very low affinity for all beta-lactam antibiotics.

Question 2

Which cytokines are the primary endogenous pyrogens responsible for fever in sepsis?

Accepted Answer

TNF-alpha and IL-1

Answer

TNF-alpha and IL-1 are the primary endogenous pyrogens released by macrophages that act on the hypothalamus via prostaglandin E2 to raise the temperature set-point.

Question 3

What initiates the classical pathway of complement activation?

Accepted Answer

C1q binding to antigen-antibody complexes

Answer

The classical pathway is initiated when C1q binds to Fc regions of IgG or IgM antibodies already bound to antigen, activating C1r and C1s.

Question 4

Which antibiotic is currently the first-line treatment for severe Clostridioides (Clostridium) difficile infection?

Accepted Answer

Oral vancomycin or fidaxomicin

Answer

Oral vancomycin or fidaxomicin is the recommended first-line treatment for C. difficile infection; oral vancomycin achieves very high intraluminal concentrations without systemic absorption.

Question 5

Which is the most significant risk factor for ventilator-associated pneumonia (VAP) in postoperative surgical patients?

Accepted Answer

Mechanical ventilation via endotracheal tube

Answer

Mechanical ventilation bypasses the natural upper airway defences and allows micro-aspiration of oropharyngeal secretions around the cuff, making it the primary risk factor for VAP.

FRCS Part A Practice Test

FRCS Part A Practice Test

FRCS Surgical Microbiology & Immunology 2