Multi-drug resistant Pseudomonas aeruginosa outbreak in a burns unit--an infection control study.

A newly introduced, multi-drug resistant (MDR) strain of Pseudomonas aeruginosa was isolated from four patients admitted to the Concord Hospital Burns Unit (BU) between December 1997 and March 1998. It was the cause of recurrent episodes of bacteraemia in two. This strain was resistant in vitro to gentamicin, piperacillin and ciprofloxacin. The isolates were confirmed as a clonal strain by pulse field gel electrophoresis (PFGE). Multiple environmental swabs were taken to search for an environmental reservoir, but no source was identified. Random cultures of staff members' hands failed to demonstrate ongoing carriage. In the absence of a demonstrable point source for the outbreak, direct cross-transmission patient to patient, via transient staff hand contamination, was the most likely route of infection. Following study commencement no new cases of infection with the MDR strain were detected. It would appear that the infection cycle has been interrupted, and the outbreak terminated following the discharge of the last infected patient from the BU. Contamination of a neutral detergent in the BU with Klebsiella oxytoca was detected incidentally during environmental surveillance. A potential hospital-wide outbreak was averted.