Carbapenem resistance due to Bla(OXA-48) among ESBL-producing Escherichia coli and Klebsiella pneumoniae isolates in a univesity hospital, Turkey.

Bacterial isolates producing Class D OXA-48 carbapenemase may be missed in routine laboratory testing, allowing them to spread undetected. The purpose of the present study was to detect bla(OXA-48) among ESBL-producing Klebsiella pneumoniae and Escherichia coli isolates collected from a university hospital, Turkey. Ninety-two ESBL-producing isolates (66 E. coli, 26 K. pneumoniae) were obtained in 2010. Antibiotic susceptibility tests were performed using the disc diffusion method and VITEK 2 system. Carbapenemase activity was screened using modified Hodge test. Beta-lactamase genes were detected by PCR and bla(OXA-48)-positive amplicons were sequenced. Genetic relatedness among K. pneumoniae isolates was investigated by pulsed-field gel-electrophoresis (PFGE). Carbapenemase activity was detected in 1 E. coli and 9 K. pneumoniae isolates and 8 of the K. pneumoniae plus the E. coli isolates were resistant to ertapenem. Three K. pneumoniae and 1 E. coli isolates were resistant to imipenem. All 10 isolates were susceptible to meropenem. bla(OXA-48) was present in all 10 isolates. Additionally, 9 isolates contained at least one beta-lactamase gene, including bla(SHV') bla(CTX-M) and bla(VEB) type. PFGE revealed different karyotypes among 9 K. pneumoniae isolates suggesting that the dissemination of bla(OXA-48) gene was not spread by a single K. pneumoniae clone. Thus OXA-48-producing isolates found in carbapenem-susceptible strains according to CLSI guidelines.