Determination of CTX-M beta-lactamase in Escherichia coli strains isolated from clinical samples

The aim of this study was to determine the ESBL with phenotypic tests and investigate the bla(CTX-M) genes with the PCR method in Escherichia coli strains. The presence of ESBL in E. coli strains was determined with the Vitek 2 automated system. ESBL-positive 100 and ESBL-negative 50 E. coli strains were included in the study. The ESBL disk diffusion screening test (DDST) and the combined disk confirmation tests (CDCT) were performed on these strains and the results of these tests were compared with each other. bla(CTX-M) genes were investigated with the PCR method. The results of CDCT-CAZ-CZC and CDCT-CTX-CTC were found to be consistent in 90% of strains. Those of the automated system, DDST and CDCT-CAZ-CZC were compatible with each other in 83.3% of strains. Also the results of the automated system and CDCT-CTX-CTC were found to be compatible in 83.3% of strains. Based on PCR, bla(CTX-M) genes were found in 67.3% of 150 strains. According to the order of frequency, 46%, 38.7%, 20%, 7.3% of strains were determined to carry groups I, IV, II and III, respectively.