English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Sir, 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. In recent years, CTX-M enzymes have become the most prevalent extended-spectrum b-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. 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. 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 30CS. Between the two copies of the 30CS is a 2.1 kb ISCR, as has been identified in In6, In7, In117, In34, In35 and In601, – 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. 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 and AF071413). 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. 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.

The blaCTX-M-1 gene located in a novel complex class I integron bearing an ISCR1 element in Escherichia coli isolates from Zhenjiang, China