RESUMO
OBJECTIVES: The aim of this study was to investigate the presence of VEB enzymes among Pseudomonas spp. referred to the UK's national reference laboratory and with phenotypic evidence of extended-spectrum beta-lactamase (ESBL) production. METHODS: Antibiograms were analysed for Pseudomonas spp. referred from November 2003 to November 2007. Isolates with >/=4-fold ceftazidime/clavulanate synergy were screened for bla(VEB) alleles. Genes encoding metallo-beta-lactamases (bla(MBL)) were sought in isolates with positive imipenem/EDTA synergy tests. Selected PCR products were sequenced. PFGE of SpeI-digested genomic DNA was used to compare isolates. RESULTS: Forty-nine (3.7%) of 1338 Pseudomonas spp. were considered potential ESBL producers; 40 were recovered for molecular testing. bla(VEB) alleles were detected in 32 Pseudomonas aeruginosa isolates, comprising diverse PFGE types, from 12 UK hospitals and 1 in India. One UK centre referred 15 isolates with VEB-1 enzyme; these were serotype O15, representing a single PFGE-defined strain that also produced VIM-10 metallo-carbapenemase. This strain was resistant to all beta-lactams, aminoglycosides and ciprofloxacin, remaining susceptible only to colistin (MICs