Abstract
Plasmid-mediated quinolone resistance (PMQR) refers to a family of closely related genes that confer decreased susceptibility to fluoroquinolones. PMQR genes are generally associated with integrons and/or plasmids that carry additional antimicrobial resistance genes active against a range of antimicrobials. In Ho Chi Minh City (HCMC), Vietnam, we have previously shown a high frequency of PMQR genes within commensal Enterobacteriaceae. However, there are limited available sequence data detailing the genetic context in which the PMQR genes reside, and a lack of understanding of how these genes spread across the Enterobacteriaceae. Here, we aimed to determine the genetic background facilitating the spread and maintenance of qnrS1, the dominant PMQR gene circulating in HCMC. We sequenced three qnrS1-carrying plasmids in their entirety to understand the genetic context of these qnrS1-embedded plasmids and also the association of qnrS1-mediated quinolone resistance with other antimicrobial resistance phenotypes. Annotation of the three qnrS1-containing plasmids revealed a qnrS1-containing transposon with a closely related structure. We screened 112 qnrS1-positive commensal Enterobacteriaceae isolated in the community and in a hospital in HCMC to detect the common transposon structure. We found the same transposon structure to be present in 71.4 % (45/63) of qnrS1-positive hospital isolates and in 36.7 % (18/49) of qnrS1-positive isolates from the community. The resulting sequence analysis of the qnrS1 environment suggested that qnrS1 genes are widely distributed and are mobilized on elements with a common genetic background. Our data add additional insight into mechanisms that facilitate resistance to multiple antimicrobials in Gram-negative bacteria in Vietnam.
Highlights
Fluoroquinolones are among the current first line of drugs in Vietnam for treating infections ranging from pneumonia to diarrhoea to bacteraemia
In a study investigating the distribution of Plasmid-mediated quinolone resistance (PMQR) determinants in Enterobacteriaceae isolated from hospitalized patients and healthy volunteers from Ho Chi Minh City (HCMC), Vietnam, we found an exceptionally high prevalence of the qnrS1 genes in both hospital (63/139, 45 %) and community (49/413, 12 %) bacterial isolates (Vien et al, 2009)
All of the strains have been described previously and were isolated from patients admitted to the tetanus ward of the Hospital for Tropical Diseases (HTD) in HCMC, Vietnam, between May and October 2004 and between June and November 2005 or from healthy volunteers participating in a typhoid vaccine study in 2005 and 2006 (Tran et al, 2010)
Summary
Fluoroquinolones are among the current first line of drugs in Vietnam for treating infections ranging from pneumonia to diarrhoea to bacteraemia. Plasmid-mediated quinolone resistance (PMQR), in the form of a qnr gene, was first described in 1998 in a Klebsiella pneumoniae isolate from a patient with urinary tract infection in North America (Martınez-Martınez et al, 1998). Since this first report, multiple studies have described a range of PMQR determinants found within the Enterobacteriaceae and other bacterial families (Strahilevitz et al, 2009). Of the five qnr genes identified, only the genetic contexts of qnrA and qnrB have been comprehensively described These genes are commonly located within complex sul1-type class 1 integrons (Garnier et al, 2006; Poirel et al, 2006). It is currently unknown if the qnrS gene is always associated with IS26 or if qnrS can be transferred and/or maintained by other, unrelated, mobile elements
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