JAC Advance Access published online on July 21, 2008
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkn300
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Research letter |
The blaCTX-M-1 gene located in a novel complex class I integron bearing an ISCR1 element in Escherichia coli isolates from Zhenjiang, China
Department of Microbiology and Immunology, Institute of Clinical Laboratory Medicine, Jiangsu University, Zhenjiang 212013, China
* Corresponding author. Tel: +86-511-5038140; Fax: +86-511-5038449; E-mail: xuhx{at}ujs.edu.cn or szl30{at}yeah.net
Key Words: E. coli , unusual class 1 integron , extended-spectrum β-lactamases , ESBLs
CTX-M enzymes include more than 60 variants belonging to five different clusters (CTX-M-1, CTX-M-2, CTX-M-8, CTX-M-9 and CTX-M-25) according to their amino acid sequence.1 In recent years, CTX-M enzymes have become the most prevalent extended-spectrum β-lactamases (ESBLs), both in nosocomial and in community settings. Different genetic elements might be involved in the mobilization of blaCTX-M genes, such as insertion sequences (ISs) ISEcp1, IS26 and IS903.1 The blaCTX-M genes have also been associated with ISCR1 (ISs common region 1, previously also called orf513), which is embedded in class 1 integrons.1,2
Class 1 integrons containing ISCR elements are known as complex class 1 integrons. They contain the classic integron structure and a second copy of the 3'CS. Between the two copies of the 3'CS is a 2.1 kb ISCR, as has been identified in In6, In7, In117, In34, In35 and In601,3–5 followed by a variable region that contains resistance genes, e.g. dfrA10, catII, blaDHA-1 (pSAL-1), blaCTX-M-9 or blaCTX-M-2,5 but never blaCTX-M-1 thus far.
Between 2005 and 2006, a total of 146 Escherichia coli isolates were obtained from the Affiliated People's Hospital of Jiangsu University. ESBL production was detected in 21/146 isolates using the standard double-disc synergy test.6 Eighty-nine of 146 (61%) isolates were found to carry class 1 integrons of different types, and 10 of these carried complex class I integrons according to the PCR analysis. The primers were designed according to the GenBank sequence (GenBank accession numbers AF174129 [GenBank] and AF071413 [GenBank] ). Five of the isolates carrying a complex class 1 integron also produced an ESBL. In these five isolates, a blaCTX-M-1 gene was detected between orf513 and an IS3000 element (Figure 1). The sequence of the complex class I integron bearing a blaCTX-M-1 gene has been submitted to GenBank under accession no. EU687490.
|
Recently, it has been suggested that ISCR1 elements were members of an extended family of IS91-like elements that can transpose adjacent DNA sequences by a mechanism termed rolling-circle transposition and are responsible for the mobilization of antibiotic resistance genes, including the blaCTX-M genes.7 However, this is the first report of a CTX-M-1 gene found to be associated with an ISCR element. The ISCR element is proposed to provide a powerful mechanism to mobilize antibiotic resistance genes, and, if this is the case, further spread of blaCTX-M-1 can be expected.
 |
Funding |
|---|
 Top Funding Transparency declarationsReferences |
|---|
This work was supported by the Foundation of Social Development of Jiangsu Province (grant no. BS2007041).
|
Transparency declarations |
|---|
|
TopFundingTransparency declarationsReferences |
|---|
None to declare.
|
Acknowledgements |
|---|
We thank Chen Qiaolin and Cheng Jing for their technical support.
|
References |
|---|
|
TopFundingTransparency declarationsReferences |
|---|
1 . Eckert C, Gautier V, Arlet G. DNA sequence analysis of the genetic environment of blaCTX-M genes. J Antimicrob Chemother (2006) 57:14–23.
2 . Cantón R, Coque TM. The CTX-M β-lactamase pandemic. Curr Opin Microbiol (2006) 9:466–75.[CrossRef][Web of Science][Medline]
3
.
Partridge SR, Hall RM. In34, a complex In5 family class 1 integron containing orf513 and dfrA10. Antimicrob Agents Chemother (2003) 47:342–9.
4
.
Valverde A, Cantón R, Galán JC, et al. In117, an unusual In0-like class 1 integron containing CR1 and blaCTX-M-2 and associated with a Tn21-like element. Antimicrob Agents Chemother (2006) 50:799–802.
5
.
Arduino SM, Roy PH, Jacoby GA, et al. blaCTX-M-2 is located in an unusual class 1 integron (In35) which includes Orf513. Antimicrob Agents Chemother (2002) 46:2303–6.
6 . Jarlier V, Nicolas MH, Fournier G, et al. Extended broad-spectrum β-lactamases conferring transferable resistance to newer β-lactam agents in Enterobacteriaceae: hospital prevalence and susceptibility patterns. Rev Infect Dis (1988) 10:867–78.[Web of Science][Medline]
7
.
Toleman MA, Bennett PM, Walsh TR. ISCR elements: novel gene-capturing systems of the 21st century? Microbiol Mol Biol Rev (2006) 70:296–316.
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||