SHV-12 extended spectrum beta-lactamase associated with high-level ceftazidime resistance in Enterobacter cloacae isolated from Thailand.

Four Enterobacter cloacae clinical isolates with reduced susceptibility to ceftazidime from two hospitals in Thailand were studied. Production of extended-spectrum beta-lactamase was confirmed by double disk synergy test and combination disk method. All isolates were highly resistant to ceftazidime but retained susceptibility to imipenem. One isolate was able to hydrolyze cefotaxime, ceftazidime and cefepime, the latter being one of the treatment choices for infection by Enterobacter spp. PCR analysis demonstrated the presence of bla(SHV12) in addition to bla(TEM-1) in all isolates suggesting that SHV-12 was associated with high-level resistance to ceftazidime in the E. cloacae isolates.