Prevalence of aac(6')-Ib-cr encoding a ciprofloxacin-modifying enzyme among Enterobacteriaceae blood isolates in
Eun Sil Kim1, Jin-Yong Jeong, Jae-Bum Jun
1Division of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Korea.
Abstract:
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.
Insights
The aminoglycoside acetyltransferase gene aac(6')-Ib was found in 15.5% of Enterobacteriaceae. A subset of these, 22%, also carried the aac(6')-Ib-cr variant, often alongside other resistance genes.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The emergence of antibiotic resistance in Enterobacteriaceae poses a significant public health threat.
- The aac(6 extquoteright)-Ib gene is a common mechanism for aminoglycoside resistance.
- The aac(6 extquoteright)-Ib-cr variant confers resistance to newer beta-lactam antibiotics.
Purpose of the Study:
- To determine the prevalence of the aac(6 extquoteright)-Ib gene in Enterobacteriaceae isolates.
- To investigate the occurrence of the aac(6 extquoteright)-Ib-cr variant within these isolates.
- To explore associations between aac(6 extquoteright)-Ib-cr and other beta-lactamase genes.
Main Methods:
- Detection of the aac(6 extquoteright)-Ib gene using molecular methods.
- Identification of the aac(6 extquoteright)-Ib-cr variant in positive isolates.
- Screening for co-occurrence of OXA-1, CTX-M-1 group, and qnrS genes.
Main Results:
- The aac(6 extquoteright)-Ib gene was detected in 15.5% (86/555) of Enterobacteriaceae.
- The aac(6 extquoteright)-Ib-cr variant was found in 22.0% (19/86) of aac(6 extquoteright)-Ib-positive isolates.
- A strong association was observed between aac(6 extquoteright)-Ib-cr and OXA-1 and CTX-M-1 group genes. One K. pneumoniae isolate harbored both aac(6 extquoteright)-Ib-cr and qnrS.
Conclusions:
- The aac(6 extquoteright)-Ib gene is prevalent in Enterobacteriaceae.
- The aac(6 extquoteright)-Ib-cr variant is present in a notable proportion of these isolates, particularly in E. coli and K. pneumoniae.
- Co-resistance mediated by the co-occurrence of aac(6 extquoteright)-Ib-cr with other beta-lactamase genes is a significant concern.
