Homogeneity of antimicrobial policy, yet heterogeneity of antimicrobial resistance: antimicrobial non-susceptibility among 108,717 clinical isolates from primary, secondary and tertiary care patients in London

J Antimicrob Chemother. 2014 Dec;69(12):3409-22. doi: 10.1093/jac/dku307. Epub 2014 Aug 12.


Objectives: We examined the 4 year trend in antimicrobial susceptibilities and prescribing across levels of care at two London teaching hospitals and their multisite renal unit, and for the surrounding community.

Methods: Laboratory and pharmacy information management systems were interrogated, with antimicrobial use and susceptibilities analysed between hospitals, within hospitals and over time.

Results: A total of 108,717 isolates from 71,687 patients were identified, with significant differences (at P < 0.05) in antimicrobial susceptibility between and within hospitals. Across the 4 years, rates of ESBL-/AmpC-producing Enterobacteriaceae ranged from 6.4% to 10.7% among community isolates, 17.8% to 26.9% at ward level and 25.2% to 52.5% in critical care. Significant variations were also demonstrated in glycopeptide-resistant enterococci (ward level 6.2%-17.4%; critical care 21.9%-56.3%), MRSA (ward level 18.5%-38.2%; critical care 12.5%-47.9%) and carbapenem-resistant Pseudomonas spp. (ward level 8.3%-16.9%; critical care 19.9%-53.7%). Few instances of persistently higher resistance were seen between the hospitals in equivalent cohorts, despite persistently higher antimicrobial use in Hospital 1 than Hospital 2. We found significant fluctuations in non-susceptibility year on year across the cohorts, but with few persistent trends.

Conclusions: The marked heterogeneity of antimicrobial susceptibilities between hospitals, within hospitals and over time demands detailed, standardized surveillance and appropriate benchmarking to identify possible drivers and effective interventions. Homogeneous antimicrobial policies are unlikely to continue to be suitable as individual hospitals join hospital networks, and policies should be tailored to local resistance rates, at least at the hospital level, and possibly with finer resolution, particularly for critical care.

Keywords: antibiograms; antimicrobial stewardship; healthcare-associated infections; multidrug-resistant organisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Anti-Bacterial Agents / therapeutic use*
  • Bacteria / drug effects*
  • Bacterial Infections / epidemiology
  • Bacterial Infections / microbiology*
  • Cohort Studies
  • Drug Resistance, Bacterial*
  • Drug Therapy / standards
  • Female
  • Health Policy
  • Hospitals, Teaching
  • Humans
  • London / epidemiology
  • Male
  • Middle Aged
  • Primary Health Care / methods
  • Secondary Care / methods
  • Tertiary Healthcare / methods
  • Young Adult


  • Anti-Bacterial Agents