MOLECULAR EPIDEMIOLOGY OF A NOSOCOMIAL OUTBREAK DUE TO SHV-4-PRODUCING STRAINS OF CITROBACTER-DIVERSUS

Over a 6-month period, eight strains of Citrobacter diversus (Citrobac ter koseri) resistant to extended-spectrum cephalosporins and monobact ams were isolated from seven colonized and/or infected patients from t he same intensive care unit, All strains harbored a single large conju gative plasmid which mediated an extended-spectrum beta-lactamase of t he SHV-4 type (ceftazidimase phenotype; enzyme pi, 7.8; plasmid DNA hy bridization with a bla(SHV)-specific probe), All strains were characte rized by antibiotic resistance pattern analysis, beta-lactamase conten t analysis, plasmid profiling, ribotyping with EcoRI, and arbitrarily primed (AP)-PCR with primers O8 and O12. Among the eight C. diversus s trains, strains Cd5 to Cd12, six isolates (isolates Cd6 to Cd11) were identical by all markers; one strain (strain Cd5) differed by two mark ers (antibiotype and AP-PCR pattern with primer O8), and the remaining strain (strain Cd12) differed by two other markers (ribotype and AP-P CR pattern with primer O12), Our results suggest that six of the eight SHV-4-producing C. diversus strains studied (strains Cd6 to Cd11) wer e a single epidemic strain, Strain Cd5 could be related to the epidemi c strain; the origin of strain Cd12 remains uncertain.