This study sought to identify mechanisms behind resistance to third-generation cephalosporins and ciprofloxacin in Irish multidrugresistant Enterobacteriaceae isolates. The most prevalent extended-spectrum beta-lactamase genes identified were bla(SHV-12) and bla(CTX-M-15) These were associated with the fluoroquinolone resistance genes aac(6')-IB-cr, qnrA, and qnrB, not previously reported in Irish isolates. (C) 2010 Elsevier Inc. All rights reserved.