Unit 6.2: Healthcare-Associated Infections (HCAIs)

• Topic 01

  MRSA Screening, Decolonisation, and Management

  46 questions
• Topic 02

  Clostridioides difficile

  46 questions
• Topic 03

  Catheter-Associated UTI Prevention

  45 questions
• Topic 04

  Surgical Site Infection Prevention Bundle

  45 questions

A few questions from this unit, with the answer and a full explanation. The complete bank is available when you start practising.

1. Why must vancomycin or fluoroquinolone prophylaxis be given earlier than standard antibiotics before incision?

   • A
     These antibiotics require slower infusion rates to prevent infusion reactions (vancomycin: red man syndrome; fluoroquinolones: QT prolongation); they must be given within 30 minutes of incision to allow adequate infusion time
     Correct answer
   • B
     Fluoroquinolones require preoperative fasting to achieve adequate plasma levels, so they must be given before food is restricted
   • C
     Vancomycin must be given earlier because it is less effective than beta-lactams and requires more time to act
   • D
     Vancomycin and fluoroquinolones have longer half-lives and achieve higher tissue levels when given earlier
   Explanation

   Vancomycin requires a slow infusion rate (no faster than 10 mg/minute) to prevent 'red man syndrome' — a histamine-mediated flushing reaction caused by rapid infusion. Similarly, fluoroquinolones can prolong the QT interval, and rapid infusion increases this risk. Because adequate infusion time must be allowed before skin incision, both agents need to be started within 30 minutes (rather than the standard 60-minute window for other antibiotics). This is a practical concern that requires advance planning by the preoperative nursing and anaesthetic team.

2. What toxins does C. difficile produce and what are their primary effects?

   • A
     Toxin A inhibits nerve transmission in the colon; Toxin B promotes bacterial spread through the bloodstream
   • B
     Toxin A (enterotoxin) disrupts tight junctions in the intestinal epithelium; Toxin B (cytotoxin) causes cell death and colonic inflammation
     Correct answer
   • C
     Toxin A destroys red blood cells; Toxin B attacks the liver causing jaundice
   • D
     Toxin A causes airway constriction; Toxin B causes haemorrhagic diarrhoea
   Explanation

   C. difficile produces two major toxins: Toxin A is an enterotoxin that disrupts the tight junctions between intestinal epithelial cells, increasing mucosal permeability and promoting fluid loss. Toxin B is a more potent cytotoxin that causes cell death and triggers a profound inflammatory response in the colon. Some hypervirulent strains (e.g., ribotype 027) also produce a binary toxin, which is associated with even more severe disease. Both toxins together drive the spectrum from mild diarrhoea to severe pseudomembranous colitis.

3. What is normothermia and why is it critical for SSI prevention?

   • A
     Normothermia is a normal theatre temperature of 21°C, maintained to keep theatre staff comfortable during long procedures
   • B
     Normothermia is a core body temperature of 36°C or above; maintaining it is critical because hypothermia impairs neutrophil function and wound perfusion, significantly increasing SSI risk
     Correct answer
   • C
     Normothermia is a temperature of exactly 37.0°C; any variation above or below this increases SSI risk equally
   • D
     Normothermia only matters intraoperatively; once the patient is in recovery, temperature management is no longer relevant to SSI risk
   Explanation

   Normothermia in the perioperative context is defined as a core body temperature of 36.0°C or above. Perioperative hypothermia (core temperature <36°C) impairs the immune response by reducing neutrophil oxidative killing capacity, decreasing tissue oxygen delivery, impairing wound collagen synthesis, and causing peripheral vasoconstriction that reduces antibiotic delivery to wound tissues. Evidence shows hypothermia significantly increases SSI rates. Active prewarming before surgery, intraoperative warming strategies, and postoperative temperature monitoring are all components of the SSI prevention bundle.