FRCS Surgical Microbiology & Immunology

Question 1

Which organism is the most common cause of surgical site infections?

Accepted Answer

Staphylococcus aureus

Answer

Escherichia coli

Answer

Pseudomonas aeruginosa

Answer

Bacteroides fragilis

Question 2

Which type of hypersensitivity reaction is responsible for anaphylaxis?

Accepted Answer

Type I (IgE-mediated)

Answer

Type II (cytotoxic)

Answer

Type III (immune complex)

Answer

Type IV (delayed)

Question 3

What is the mechanism of action of beta-lactam antibiotics?

Accepted Answer

Inhibition of bacterial cell wall synthesis by binding penicillin-binding proteins

Answer

Inhibition of bacterial protein synthesis at the 30S ribosome

Answer

Disruption of the bacterial cell membrane

Answer

Inhibition of bacterial DNA gyrase

Question 4

Which Clostridium species is the primary causative organism of gas gangrene (clostridial myonecrosis)?

Accepted Answer

Clostridium perfringens

Answer

Clostridium difficile

Answer

Clostridium tetani

Answer

Clostridium botulinum

Question 5

Which cells are the primary effector cells of innate immunity?

Accepted Answer

Neutrophils and macrophages

Answer

B lymphocytes and plasma cells

Answer

CD4+ and CD8+ T lymphocytes

Answer

Natural killer T cells exclusively

Question 6

What is the precise definition of bacteraemia?

Accepted Answer

The presence of viable bacteria in the bloodstream

Answer

Bacteria multiplying in the bloodstream with associated systemic inflammatory signs

Answer

Bacterial endotoxins circulating in the bloodstream

Answer

A positive urine culture with more than 10^5 organisms/mL

Question 7

Which sterilisation method is most appropriate for heat-sensitive surgical equipment such as fibreoptic endoscopes?

Accepted Answer

Ethylene oxide (ETO) gas sterilisation

Answer

Autoclaving at 134°C for 3 minutes

Answer

Dry heat oven at 160°C for 2 hours

Answer

Glutaraldehyde high-level disinfection only