Molecular epidemiology of the integron-located VEB-1 extended-spectrum beta-lactamase in nosocomial enterobacterial isolates in Bangkok, Thailand

Over a 21/2-month period in 1999, 37 ceftazidime-resistant nonrepetitive en terobacterial isolates were collected from 37 patients in a Bangkok hospita l, Thailand. Eighty-one percent of these strains expressed a clavulanic aci d-inhibited extended-cephalosporin resistance profile. An identical extende d-spectrum beta -lactamase (ESBL), VEB-1, was found in 16 unrelated enterob acterial isolates (Escherichia coli, n = 10; Enterobacter cloacae, n = 2; E nterobacter sakazakii, n = 1; and Klebsiella pneumoniae, n = 3) and in two clonally related E. cloacae isolates. The bla(VEB-1) gene was located on mo stly self-conjugative plasmids (ca. 24 to 200 kb) that conferred additional non-p-lactam antibiotic resistance patterns. Additionally, the bla(VEB-1) gene cassette was part of class 1 integrons varying in size and structure. The bla(VEB-1)-containing integrons were mostly associated with bla(OXA-10) -like and arr-2-like gene cassettes, the latter conferring resistance to ri fampin. These data indicated the spread of bla(VEB-1) in Bangkok due to fre quent transfer of different plasmids and class 1 integrons and rarely to cl onally related strains. Plasmid and integron-mediated resistance to rifampi n was also found in enterobacterial isolates.