PCR Classification of CTX-M-Type β-Lactamase Genes Identified in Clinically Isolated Gram-Negative Bacilli in Japan

Of 1,456 strains isolated from 2001 to 2003 demonstrating resistance to either oxyimino-cephalosporin, 317 strains, isolated in 57 of 132 clinical facilities, were found to harbor bla(CTX-M) genes by PCR. Fifty-seven, 161, and 99 strains harbored bla(CTX-M) genes belonging to the bla(CTX-M-1), bla(CTX-M-2), and bla(CTX-M-9) clusters, respectively.