In34, a Complex In5 Family Class 1 Integron Containing orf513 and dfrA10

Abstract

A complex class 1 integron, In34, found in a conjugative plasmid from a multidrug-resistant Klebsiella pneumoniae strain isolated in 1997 at a hospital in Sydney, Australia, was shown to have a backbone related to that of In2, which belongs to the In5 family. In In34, the aadB gene cassette replaces the aadA1a cassette in In2, and two additional resistance genes, dfrA10 and aphA1, that are not part of a gene cassette are present. The aphA1 gene is in a Tn4352-like transposon that is located in the tniA gene. The dfrA10 gene lies adjacent to a 2,154-bp DNA segment, known as the common region, that contains an open reading frame predicting a product of 513 amino acids (Orf513). Orf513 is 66 and 55% identical to the products of two further open reading frames that, like the common region, are found adjacent to antibiotic resistance genes. A 27-bp conserved sequence was found at one end of each type of common region. The loss of dfrA10 due to homologous recombination between flanking direct repeats and incorporation of the excised circle by homologous recombination were demonstrated. Part of In34 is identical to the sequenced portion of In7, which is from a multidrug-resistant Escherichia coli strain that had been isolated 19 years earlier in the same hospital. In34 and In7 are in plasmids that contain the same six resistance genes conferring resistance to ampicillin, chloramphenicol, gentamicin, kanamycin, neomycin, tobramycin, trimethoprim, and sulfonamides, but the plasmid backbones appear to be unrelated, suggesting that translocation of a multiple-drug-resistance-determining region as well as horizontal transfer may have occurred.

blaCTX-M-2 and blaCTX-M-28 extended-spectrum β-lactamase genes and class 1 integrons in clinical isolates of Klebsiella pneumoniae from Brazil

“…Among Enterobacteriaceae, these resistances were commonly associated with a few types of integrons, mainly class 1 and 2 (Bissonnette & Roy 1992, Partridge & Hall 2003. In this study, two isolates that carried the gene bla CTX-M-2 (K16R and K18P) also contained class 1 integrons with the gene cassettes aadA1 or bla , which encode the enzymes aminoglycoside-3´-adenyltransferase and oxacillinase type 2, respectively.…”

“…Insertion sequences (IS), such as ISEcp1, IS10, IS26 and IS903, might be involved in the mobilisation of bla CTX-M genes (Bonnet et al 2000, Saladin et al 2002. bla CTX-M genes have also been associated with ISCR1 (IS common region 1, previously also called orf513), which is often found downstream of complex class 1 integrons (Partridge & Hall 2003).…”

Diversity of genotypes in CTX-M-producing Klebsiella pneumoniae isolated in different hospitals in Brazil

“…21 The bla CTX-M genes have also been associated with ISCR1, which is often found downstream of complex class 1 integrons. 22 CTX-M-2, CTX-M-8 and CTX-M-9 groups were the most frequently detected CTX-M-type enzymes among ESBL-producing Enterobacteriaceae isolates from South American countries. 4,9,23 In the present study, CTX-M 2 (61%) was the predominant cluster.…”

Emergence of Salmonella epidemics: The problems related to Salmonella enterica serotyp Enteritidis and multiple antibiotic resistance in other major serotypes

“…Following this unique region is a second partial copy of the 3'-CS, designated 3'-CS2. The CR itself contains a gene, designated orf513, whose deduced product is thought to be a putative transposase [22], which is postulated to interact with the 27-bp boundary sequence and mobilise antibiotic resistance genes [113].…”