The First Swedish Outbreak with VIM-2-Producing Pseudomonas aeruginosa, Occurring between 2006 and 2007, Was Probably Due to Contaminated Hospital Sinks

Abstract

Multidrug-resistant Pseudomonas aeruginosa is an increasing clinical problem worldwide. The aim of this study was to describe the first outbreak of a Verona integron-borne metallo-ß-lactamase (VIM)-2-producing P. aeruginosa strain in Sweden and its expansion in the region. A cluster of multidrug-resistant P. aeruginosa appeared at two neighbouring hospitals in 2006. The isolates were characterized by PCR, pulsed-field gel electrophoresis (PFGE), and whole-genome sequencing. Patient charts, laboratory records, and hygiene routines were reviewed, and patients, staff, and the environment were screened. The investigation revealed a clonal outbreak of a VIM-2-producing P. aeruginosa strain belonging to the high-risk clonal complex 111, susceptible only to gentamicin and colistin. No direct contact between patients could be established, but most of them had stayed in certain rooms/wards weeks to months apart. Cultures from two sinks yielded growth of the same strain. The outbreak ended when control measures against the sinks were taken, but new cases occurred in a tertiary care hospital in the region. In conclusion, when facing prolonged outbreaks with this bacterium, sinks and other water sources in the hospital environment should be considered. By implementing proactive control measures to limit the bacterial load in sinks, the waterborne transmission of P. aeruginosa may be reduced.

Keywords: MBL; Pseudomonas aeruginosa; VIM-2; nosocomial outbreak; sink.

Figure 1

Pulsed-field gel electrophoresis of the patient isolates. Lanes 1 and 12: DNA size markers; lanes 2 and 11: a control strain; and lanes 3–10: patient isolates from the outbreak in the same order as they were isolated.

Figure 2

Illustration of the class I integron (2518 bp) of the outbreak strain. Abbreviations: intl—class integrase gene; P_c and P_int—gene cassette promotors; attI—integron-associated recombination site; ORF—open reading frame; attC—recombination site of the gene cassette; VIM-2—Verona integron-borne metallo-ß-lactamase-2.

Figure 3

Wards visited by the patients involved in the outbreak. Med A and B—wards in the Department of Medicine, Surg A and B—ward in the Department of Surgery, ICU—intensive care unit, KnH—Karlshamn hospital, KaH—Karlskrona Hospital.