title: Multiresistant Pseudomonas aeruginosa serogroup O:11 outbreak in an intensive care unit.
abstract: OBJECTIVE: To determine whether 15 multiresistant Pseudomonas aeruginosa isolates from an intensive care unit (ICU) outbreak were related, were endemic, and belonged to the O:12 European clone. METHODS: Forty-six P. aeruginosa isolates from a large hospital were investigated with respect to their antibiotic resistance profiles, serogroups, bacteriocin types and DNA fingerprints obtained by pulsed-field gel electrophoresis (PFGE) of genomic DNA digested with Xbal. RESULTS: Fourteen of the ICU outbreak isolates were indeed identical with respect to their serogroup, O:11, pyocin type, 10/a, and PFGE type, A. Clone A was endemic and dominant throughout the hospital, even though, within the ICU, it underwent phenotypic alterations, such as loss of cell wall lipopolysaccharide side-chains, or acquisition of ceftazidime and imipenem resistance. Bacteriocin typing was more discriminatory than serotyping, but PFGE could differentiate further among phenotypically identical strains. It also allowed the tracking of an O:6 strain, as it was becoming gradually more resistant and undergoing a bacteriocin-type conversion while remaining genotypically unaltered. CONCLUSIONS: Using three typing methods, a nosocomial multiresistant strain distinct from the previously described dominant European O:12 clone was characterized, and the ability of PFGE to identify clonal isolates even when these appear phenotypically distinct was demonstrated.
authors.affiliation: Department of Microbiology, Medical School, University of Athens.
authors.forename: Panayotis T.
authors.initials: PT
authors.lastname: Tassios
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Gennimata
authors.forename: Lemonia
authors.initials: L
authors.lastname: Spaliara-Kalogeropoulou
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kairis
authors.forename: Chryssa
authors.initials: C
authors.lastname: Koutsia
authors.forename: Alkiviadis C.
authors.initials: AC
authors.lastname: Vatopoulos
authors.forename: Nicholas J.
authors.initials: NJ
authors.lastname: Legakis