Molecular epidemiology of a multiresistant pseudomonas aeruginosa outbreakin a paediatric intensive care unit

After isolation of multiresistant (MR) Pseudomonas aeruginosa from 3 hospit alized patients in a paediatric intensive care unit (PICU), a prospective s urveillance programme was established to detect infected and/or colonized p atients in the hospital. Isolates were examined by means of outer membrane protein (OMP) profiles, serotyping and DNA genomic analysis using pulsed-fi eld gel electrophoresis (PFGE). Fifty-five P. aeruginosa strains were isola ted from 23 hospitalized patients during September and October 1997. The me dian hospital stay before isolation of P. aeruginosa was 8 d. PFGE demonstr ated that the same clone infected 14 patients, 4 of whom were not hospitali zed in the PICU. Susceptibility patterns and OMP profiles correlated with P FGE results in 37.8% and 36.4% of cases, respectively. Serotype O11 correla ted with pattern A in 77% of cases and serotype O4 correlated with unrelate d strains in 75% of cases but did not discriminate between outbreak and. p unrelated isolates. Extensive investigation of cultures failed to identify a reservoir of P. aeruginosa. PFGE was superior to OMP analysis and serotyp ing for discriminating between strains. The possible mode of acquisition fo r most of the patients infected with the same clone was cross-contamination .