Question 30

Discuss the Extended Spectrum Beta-Lactamase producing micro-organisms (ESBL) under thefollowing headings:
a) List six ESBL producing micro-organisms commonly encountered in the ICU.
(30% marks)
b) List four risk factors for ESBL producing micro-organism development. (20% marks)
c) Outline infection control measures for ESBL producing micro-organisms. (50% marks)

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College answer

Aim: To allow the candidate to demonstrate familiarity with multi-resistant organisms.
Key sources include: Papers 2014.1 Q3.3, 2009.1 Q 25.2 CanMEDS Medical Expert.
Discussion: This is a core topic with increasing importance in current ICU practice. The overall standard of response to this question was commendable. Expert answers included a thorough detailing of infection control measures and listing the relevant organisms. Candidates who failed to gain marks did so mainly in part b) with a knowledge deficit in relation to the risks of ESBL development. 



Question 3.3 from the first paper of 2014 and Question 25.2 from the first paper of 2009 all asked about ESCAPPM organisms:

  • Enterobacter
  • Serratia
  • Citrobacrter
  • Acinetobacter (and Aeromonas)
  • Proteus
  • Providencia
  • Morganella

Other organisms that can carry ESBL include  Chromobacterium violaceum,  EnterobacterE. coliHafnia alvei, Lysobacter lactamgenusOchrobactrum anthropiProteus rettgeri,  Pseudomonas aeruginosaPsychrobacter immobilis, Rhodobacter sphaeroides and Yersinia enterocolitica, as well as potentially Salmonella, Neisseria, Burkholderia and Shigella; but they only asked for six. Every article you google has a list of approximately these dimensions


"risk factors for ESBL producing micro-organism development" could potentially have meant a whole variety of different things, but most probably meant "what are the risk factors for being colonised with an ESBL-producing organism". Otter et al (2019), looking at the data from a universal screening program in London, and Ben-Ami et al (2009) analysing coimmunity patient data identified the following:

  • Number of courses of antibiotics in the last 6 months  (>2)
  • Travel to Asia or Africa in the previosu 12 motnhs
  • Overseas hospital stay in the past 12 months
  • Residence in a long-term care facility
  • Recent hospitalization
  • Age ⩾65 years
  • Male sex
  • Multiple comorbidities


This requires a list of standard contact precautions for critically ill patients:

  • Single rooms
    • Or, cohort patients with the same pathogen in the same room
    • Ensure patients are separated by more than 1m
    • Change protective attire and perform hand hygiene between contact with patients in the same room
  • PPE
    • Wear gloves whenever touching the patient’s intact skin
    • Wear a gown whenever anticipating that clothing will have direct contact with the patient
  • Limit transport and movement of patients outside of the room
  • Use disposable equipment
  • Daily cleaning and disinfection of patient rooms, with a focus on frequently-touched surfaces
  • Hand hygiene before and after all patient contact


Chaudhary, U., and R. Aggarwal. "Extended spectrum β-lactamases (ESBL)–An emerging threat to clinical therapeutics." Indian journal of medical microbiology 22.2 (2004): 75-80.

Otter, J. A., et al. "Individual-and community-level risk factors for ESBL Enterobacteriaceae colonization identified by universal admission screening in London." Clinical Microbiology and Infection 25.10 (2019): 1259-1265.

Ben-Ami, Ronen, et al. "A multinational survey of risk factors for infection with extended-spectrum β-lactamase-producing Enterobacteriaceae in nonhospitalized patients." Clinical Infectious Diseases 49.5 (2009): 682-690.

Eggimann, Philippe, and Didier Pittet. "Infection control in the ICU." Chest 120.6 (2001): 2059-2093.

CDC Guidelines for Isolation Precautions