Dominance of blaCTX-M within an Australian extended-spectrum beta-lactamase gene pool.

bla(CTX-M) genes, particularly bla(CTX-M-15), are the dominant extended-spectrum beta-lactamase (ESBL) genes among clinical isolates of Escherichia coli and Klebsiella pneumoniae in Sydney, Australia, where we also found one example of bla(CTX-M-62), encoding a novel enzyme conferring ceftazidime resistance. ESBL genes were present in diverse community isolates and in a variety of associated conjugative plasmids.