Nosocomial outbreak of VIM-2 metallo-β-lactamase-producing Pseudomonas aeruginosa associated with retrograde urography

Pseudomonas aeruginosa is well adapted to the hospital setting and can cause a wide array of nosocomial infections that occasionally culminate in recalcitrant outbreaks. In the present study, we describe the first nosocomial outbreak of infection caused by blaVIM-2-positive P. aeruginosa in Germany. In November and December 2007, highly resistant P. aeruginosa isolates were recovered from the urine of 11 patients in the Department of Urology of a University Hospital. Bacterial isolates were typed by multilocus sequence typing and screened for known metallo-β-lactamase (MBL) genes by PCR. Environmental sources of transmission were tested for bacterial contamination using surveillance cultures. Furthermore, a matched case-control study was performed in search of medical procedures significantly associated with case status. Typing of recovered isolates confirmed VIM-2 MBL-producing P. aeruginosa of sequence type 175 in all cases. Surveillance cultures did not lead to the identification of an environmental source of the outbreak strain. Case-control analysis revealed retrograde urography as the only exposure significantly associated with case status. The analyses suggest the transmission of a single clone of VIM-2 MBL-producing P. aeruginosa leading to the infection of 11 patients within 47 days. Events in temporal proximity to retrograde urographies appear to have facilitated infection in the majority of cases. Department-specific infection control measures, including reinforced hygiene procedures during retrograde urography, quickly terminated the outbreak.