FRCS Surgical Microbiology & Immunology 3

Question 1

What is the primary mechanism of action of ciclosporin in post-transplant immunosuppression?

Accepted Answer

Inhibition of calcineurin, preventing NFAT-mediated IL-2 gene transcription

Answer

Ciclosporin binds cyclophilin and the complex inhibits calcineurin, preventing dephosphorylation of NFAT and thus blocking IL-2 transcription and T-cell proliferation.

Question 2

Which organism is the causative agent of cat-scratch disease?

Accepted Answer

Bartonella henselae

Answer

Bartonella henselae is the causative organism of cat-scratch disease, typically producing regional lymphadenopathy following a scratch or bite from an infected cat.

Question 3

What is the Gram stain appearance and arrangement of Streptococcus pyogenes (Group A Streptococcus)?

Accepted Answer

Gram-positive cocci arranged in chains

Answer

Streptococcus pyogenes is a Gram-positive coccus that characteristically arranges in chains; the prefix 'strepto-' is derived from the Greek for twisted chain.

Question 4

Which fungal organism is most commonly responsible for invasive fungal infections in immunosuppressed or critically ill surgical patients?

Accepted Answer

Candida albicans

Answer

Candida albicans is the most common fungal pathogen in immunocompromised and critically ill patients, particularly those with prolonged central venous catheterisation or broad-spectrum antibiotic use.

Question 5

What is the principal aim of prophylactic antibiotics administered in clean-contaminated surgery?

Accepted Answer

To reduce the bacterial inoculum at the operative site below the threshold for infection

Answer

Surgical antibiotic prophylaxis aims to reduce the bacterial load at the operative site to a level below that required to overcome host defences and establish infection.

FRCS Part A Practice Test

FRCS Part A Practice Test

FRCS Surgical Microbiology & Immunology 3