Why cannot a β-lactamase gene be detected using an efficient molecular diagnostic method?

OBJECTIVE: Fast detection of β-lactamase (bla) genes can minimize the spread of antibiotic resistance. Although several molecular diagnostic methods have been developed to detect limited bla gene types, these methods have significant limitations, such as their failure to detect almost all clinically available bla genes. We have evaluated a further refinement of our fast and accurate molecular method, developed to overcome these limitations, using clinical isolates. METHODS: We have recently developed the efficient large-scale bla detection method ((large-scale)blaFinder) that can detect bla gene types including almost all clinically available 1,352 bla genes with perfect specificity and sensitivity. Using this method, we have evaluated a further refinement of this method using clinical isolates provided by International Health Management Associates, Inc. (Schaumburg, Illinois, USA). Results were interpreted in a blinded manner by researchers who did not know any information on bla genes harbored by these isolates. RESULTS: With only one exception, the (large-scale)blaFinder detected all bla genes identified by the provider using microarray and multiplex PCR. In one of the Escherichia coli test isolates, a bla(DHA-1) gene was detected using the multiplex PCR assay but it was not detected using the (large-scale)blaFinder. CONCLUSION: The truncation of a bla(DHA-1) gene is an important reason for an efficient molecular diagnostic method ((large-scale)blaFinder) not to detect the bla gene.