SHV-12, SHV-5, SHV-2a and VEB-1 extended-spectrum beta-lactamases in Gram-negative bacteria isolated in a university hospital in Thailand

Abstract

Sixty-one extended-spectrum β-lactamase (ESBL)-producing isolates were collected from Srinagarind Hospital, Thailand. These included 43 Enterobacteriaceae and 18 Pseudomonadaceae. The 43 Enterobacteriaceae were found to produce the following ESBLs: 26 (60.5%) SHV-12, 13 (30.2%) SHV-5, two (4.7%) SHV-2a, one (2.3%) VEB-1 and one (2.3%) unidentified. Twenty-four isolates (55.8%) also carried bla_TEM-1B, as well as bla_SHV or bla_VEB-1. Plasmid DNA from transconjugants carrying the bla_SHV-12 gene showed various restriction patterns, indicating the distribution of the bla_SHV-12 gene among different antibiotic resistance plasmids. In contrast, bla_SHV-5 in 13 isolates was found on a single plasmid of c. 130 kb. Pulsed-field gel electrophoresis (PFGE) analysis of genomic DNA from these isolates revealed that nine of 11 Klebsiella pneumoniae gave the same pattern, indicating clonal spread of the strain within the hospital, together with the occasional spread of the plasmid to other strains. Among the pseudomonad isolates, 16 Pseudomonas aeruginosa and one Pseudomonas putida had bla_VEB-like and one P. aeruginosa had bla_SHV-12. Nine of the 16 isolates carrying bla_VEB-like (56.3%) had identical PFGE patterns, suggesting the dissemination of this gene, also by clonal spread. At least six different bla_VEB-like-containing integrons were found among the 18 isolates. This is the first report of bacteria producing SHV-12 and SHV-2a in Thailand and the first report of SHV-12 in P. aeruginosa, of VEB-1 in Citrobacter freundii and a VEB-1-like β-lactamase in P. putida. These findings indicate that ESBL genes in the Far East are part of a gene pool capable of broad horizontal gene transfer, in that these genes can transfer between different families of Gram-negative bacilli.