Molecular characteristics of extended-spectrum ß-lactamase-producing Escherichia coli in Japan: emergence of CTX-M-15-producing E. coli ST131.

We investigated the molecular characteristics of ESBL-producing Escherichia coli in Japan. A total of 101 clinical isolates of ESBL-positive E. coli collected in Japan between June 2008 and November 2009 were studied. Among the 101 strains, 97 were positive for CTX-M, while 47 and two were positive for TEM and SHV, respectively. Sequencing revealed that CTX-M-14 was most common (49/101), followed by CTX-M-27 (22/101) and CTX-M-15 (8/101). Based on MLST data, seven of eight CTX-M-15 producers belonged to ST131. This is the first report about clinical isolates of E. coli ST131 possessing CTX-M-15 in Japan.