Multiresistant Pseudomonas aeruginosa serogroup O:11 outbreak in an intensive care unit.
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.
Tassios
Panayotis T.
PT
Department of Microbiology, Medical School, University of Athens.
Gennimata
Vassiliki
V
Spaliara-Kalogeropoulou
Lemonia
L
Kairis
Dimitris
D
Koutsia
Chryssa
C
Vatopoulos
Alkiviadis C.
AC
Legakis
Nicholas J.
NJ