Multiplex PCR for rapid detection of genes encoding CTX-M extended-spectrum β-lactamases

Sir, CTX-M extended-spectrum b-lactamases (ESBLs) are increasingly prevalent worldwide among Escherichia coli and Klebsiella spp., including in the UK, where over half of all microbiology laboratories have encountered producers. 1,2 More than 40 CTX-M b-lactamases have been described and are divided into five phylogenetic groups, with different groups prevalent in different countries. 3 However, characterization of the bla CTX-M alleles present in clinical isolates is time-consuming, typically requiring multiple PCRs with universal and then group-specific primers. o facilitate monitoring, we sought to develop a multiplex assay to differentiate alleles belonging to these five phylogenetic groups.