Dissemination in Portugal of CTX-M-15-, OXA-1-, and TEM-1-Producing Enterobacteriaceae Strains Containing the aac(6 ′ )-Ib-cr Gene, Which Encodes an Aminoglycoside- and Fluoroquinolone-Modifying Enzyme

CTX-M-15, recently detected in Portugal, is an extended-spectrum β-lactamase (ESBL) that has spread worldwide (3, 4, 9, 10, 15). The basis for the successful dissemination of blaCTX-M-15 is unknown, although the spread of epidemic Escherichia coli strains and/or conjugative plasmids harboring blaCTX-M-15 has been documented (3, 6).