Analysis of Clinical Isolates of Extended-Spectrum β-Lactamase-Producing Bacteria with Primer and Probe Sets Developed to Detect blaCTX-M, blaTEM, and blaSHV Using a Fully Automated Gene Detection System.

In this study, we evaluated extended-spectrum β-lactamase (ESBL)-producing bacteria with the newly developed primer and probe sets to detect blaCTX-M, blaTEM, and blaSHV using BD MAXTM, a fully automated multiplex polymerase chain reaction assay system. In 36 isolates confirmed by whole-genome sequencing to have blaCTX-M, blaTEM, or blaSHV, the developed primer and probe sets accurately detected each gene without being influenced by the presence of other β-lactamase genes. In nine control strains that do not harbor either blaCTX-M, blaTEM, or blaSHV no cross-reaction was observed. In 191 strains phenotypically determined to be ESBL-producers by conventional antimicrobial susceptibility tests, 189 strains were blaCTX-M-, blaTEM-, or blaSHV-positive as assessed by BD MAXTM using the developed primer and probe sets, and two strains were negative for these genes. Whole-genome sequencing revealed that these two strains were phenotypically false-positive ESBL-producers. The accuracy of the primer and probe sets seems to be satisfactory, and they may be applicable to detect CTX-M-type ESBL-producing bacteria.