Abstract
Background Klebsiella pneumoniae strains carrying class 1 integrons are becoming more common worldwide, and their role in the dissemination of drug resistance is significant. The aim of this study was to characterize the structural diversity of class 1 integrons and their associated gene cassettes in K. pneumoniae isolates from hospital settings.Methodology/Principal FindingsWe analyzed a total of 176 K. pneumoniae isolates in a tertiary-care hospital in Beijing, China for the period of November 1, 2010-October 31, 2011. The presence of class 1 integrons and gene cassettes was analyzed by PCR and sequencing. The prevalence of class 1 integrons was 51.1% (90/176). Fourteen different gene cassettes and 10 different gene cassette arrays were detected. dfrA and aadA cassettes were predominant and cassette combination dfrA1-orfC was most frequently found (13.6%, 24/176). Strong association between resistance to a variety of drugs (both phenotypes and the associated genes) and the presence of class 1 integrons was observed. In addition, we also identified an association between some previously identified prevalent sequence types (such as ST11, ST15, ST147, ST562, and ST716) and the presence of class 1 integrons.Conclusions/SignificanceData from this study demonstrated that class 1 integrons are highly diverse and are associated with a variety of drug resistance phenotypes, drug resistance genes, as well as genotypes among K. pneumoniae isolates. Continuous monitoring of gene cassettes in class 1 integrons is warranted to improve the understanding and control of drug resistance among hospital settings.
Highlights
The widespread use of antibiotics coupled with the intra- and inter-species transfer of resistance determinants mediated by plasmids, transposons and gene cassettes in integrons have contributed to the rapid transmission of drug resistance in bacterial pathogens, especially among members of the Enterobacteriaceae family [1,2,3,4]
The proportion of the isolates belonging to the following sequence types were higher among class 1 integron positive isolates than class 1 integron negative isolates: ST11 (7.8% vs. 3.5%), ST15 (14.4% vs. 7.0%), ST147 (11.1% vs. 0), ST562 (11.1% vs. 4.7%), and ST716 (11.1% vs. 2.3%)
An integron of about 1,171bp with the dfrA1 and orfC genes, which was present in 24 K. pneumoniae isolates, was the predominant integron gene cassette array detected
Summary
The widespread use of antibiotics coupled with the intra- and inter-species transfer of resistance determinants mediated by plasmids, transposons and gene cassettes in integrons have contributed to the rapid transmission of drug resistance in bacterial pathogens, especially among members of the Enterobacteriaceae family [1,2,3,4]. The most frequently identified gene cassettes within class 1 integrons in Enterobacteriaceae are those encode resistance to streptomycin (aadA) and trimethoprim (dfrA) [5]. The aim of this study was to characterize the structural diversity of class 1 integrons and their associated gene cassettes in K. pneumoniae isolates from hospital settings. Strong association between resistance to a variety of drugs (both phenotypes and the associated genes) and the presence of class 1 integrons was observed. We identified an association between some previously identified prevalent sequence types (such as ST11, ST15, ST147, ST562, and ST716) and the presence of class 1 integrons. Conclusions/Significance: Data from this study demonstrated that class 1 integrons are highly diverse and are associated with a variety of drug resistance phenotypes, drug resistance genes, as well as genotypes among K. pneumoniae isolates. Continuous monitoring of gene cassettes in class 1 integrons is warranted to improve the understanding and control of drug resistance among hospital settings
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