Association of IS5 with divergent tandem bla CMY-2 genes in clinical isolates of Escherichia coli

• Published in: Journal of antimicrobial chemotherapy 2011-08, Vol.66 (8), p.1734-1738
• Main Authors: Kurpiel, Philip M., Hanson, Nancy D.
• Format: Article
• Language: English
• ISSN: 0305-7453; 1460-2091
• DOI: 10.1093/jac/dkr212

Objective To characterize a unique tandem bla CMY-2 gene arrangement found in two non-identical clinical strains of Escherichia coli. Methods Both plasmid and chromosomal DNA were evaluated using PFGE, restriction digest analysis, plasmid profiling and Southern hybridization. bla CMY-2 gene expression and gene copy number were evaluated by real-time PCR. Susceptibilities to selected β-lactam antibiotics were determined by agar dilution. Results A tandem arrangement for bla CMY-2 was identified in both isolates and was the only arrangement for bla CMY-2 observed. These isolates had distinct PFGE and plasmid profiles. Each strain exhibited 2-fold higher bla CMY-2 mRNA expression and up to 8-fold lower β-lactam susceptibility compared with a strain with a single copy of bla CMY-2. Conclusion This is the first report of IS5 being associated with tandem bla CMY-2. IS5 has previously been associated with antibiotic resistance through tandem gene amplification. The unique tandem arrangement provides a mechanism for increased bla CMY-2 expression.