Outbreak of Pseudomonas aeruginosa producing VIM carbapenemase in an intensive care unit and its termination by implementation of waterless patient care

Crit Care. 2021 Aug 19;25(1):301. doi: 10.1186/s13054-021-03726-y.


Background: Long-term outbreaks of multidrug-resistant Gram-negative bacilli related to hospital-building water systems have been described. However, successful mitigation strategies have rarely been reported. In particular, environmental disinfection or replacement of contaminated equipment usually failed to eradicate environmental sources of Pseudomonas aeruginosa.

Methods: We report the investigation and termination of an outbreak of P. aeruginosa producing VIM carbapenemase (PA-VIM) in the adult intensive care unit (ICU) of a Swiss tertiary care hospital with active case finding, environmental sampling and whole genome sequencing (WGS) of patient and environmental strains. We also describe the implemented control strategies and their effectiveness on eradication of the environmental reservoir.

Results: Between April 2018 and September 2020, 21 patients became either infected or colonized with a PA-VIM strain. For 16 of them, an acquisition in the ICU was suspected. Among 131 environmental samples collected in the ICU, 13 grew PA-VIM in sink traps and drains. WGS confirmed the epidemiological link between clinical and environmental strains and the monoclonal pattern of the outbreak. After removing sinks from patient rooms and implementation of waterless patient care, no new acquisition was detected in the ICU within 8 months after the intervention.

Discussion: Implementation of waterless patient care with removal of the sinks in patient rooms was successful for termination of a PA-VIM ICU outbreak linked to multiple environmental water sources. WGS provides highly discriminatory accuracy to investigate environment-related outbreaks.

Keywords: Aquatic reservoir; Carbapememase; Outbreak; Pseudomonas aeruginosa; Sink; VIM; Waterless; cgMLST.

MeSH terms

  • Adult
  • Aged
  • Bacterial Proteins / pharmacology
  • Bacterial Proteins / therapeutic use*
  • Cross Infection / epidemiology
  • Disease Outbreaks / statistics & numerical data
  • Epidemiology
  • Equipment Contamination
  • Female
  • Humans
  • Iatrogenic Disease / epidemiology
  • Intensive Care Units / organization & administration
  • Intensive Care Units / statistics & numerical data
  • Male
  • Middle Aged
  • Pseudomonas Infections / drug therapy
  • Pseudomonas Infections / epidemiology
  • Pseudomonas Infections / genetics*
  • Pseudomonas aeruginosa / drug effects*
  • Pseudomonas aeruginosa / genetics
  • Switzerland / epidemiology
  • beta-Lactamases / pharmacology
  • beta-Lactamases / therapeutic use*


  • Bacterial Proteins
  • beta-Lactamases
  • carbapenemase