Prevalence of aac(6′)-Ib-cr Encoding a Ciprofloxacin-Modifying Enzyme among Enterobacteriaceae Blood Isolates in Korea

The aac(6')-Ib gene was detected in 86 of 555 (15.5%) Enterobacteriaceae isolates. Among these 86 aac(6')-Ib-positive isolates, 19 (22.0%) were positive for aac(6')-Ib-cr: 4 of 31 (12.9%) Enterobacter spp., 7 of 13 (53.8%) Escherichia coli isolates, and 8 of 42 (19.0%) Klebsiella pneumoniae isolates. There was a strong association between aac(6')-Ib-cr and OXA-1 and CTX-M-1 group beta-lactamase genes. One aac(6')-Ib-positive K. pneumoniae isolate carried both aac(6')-Ib-cr and qnrS.