Abstract
The presence of antibiotic resistance genes (ARGs) including those expressing ESBLs and AmpC-β-lactamases in Escherichia coli inhabiting the aquatic environments is a serious health problem. The situation is further complicated by the fact that ARGs can be easily transferred among bacterial species with the help of mobile genetic elements – plasmids, integrons, insertion sequences (IS), and transposons. Therefore, the analysis of genetic environment and mobile genetic elements associated with ARGs is important as these provide useful information about the epidemiology of these genes. In our previous study, we had reported presence of various β-lactam resistance genes present in E. coli strains inhabiting the river Yamuna traversing the National Capital Territory of Delhi (India). In the present study, we have analyzed the genetic environment of three ARGs blaTEM-1, blaCTX-M-15, and blaCMY -42 of those E. coli strains. The structure of class 1 integrons and their gene cassettes was also analyzed. Insertion sequence IS26 was present upstream of blaTEM-1, ISEcp1 was present upstream of blaCTXM-15 gene and orf477 was present downstream of blaCTXM-15. ISEcp1 was also present upstream of blaCMY -42 and, blc and sugE genes were present in the downstream region of this gene. Thus, the overall genetic environment surrounding these genes was similar to that reported from E. coli strains isolated globally. Conjugation assays, isolation and analysis of plasmid DNA of the transconjugants indicated that blaTEM-1, blaCTX-M-15, blaCMY -42 and class 1 integron were plasmid-mediated and possibly transmit between genera through horizontal gene transfer (HGT). This might lead to dissemination of antimicrobial resistance genes in aquatic environment. The work embodied in this paper is the first describing the genetic environment of bla and integrons in aquatic E. coli isolated from India.
Highlights
Extensive use of third-generation cephalosporins for humans and veterinary purposes has led to an increased incidence and distribution of extended spectrum β-lactamases (ESBLs) and AmpC in bacteria (Bradford, 2001; Philippon et al, 2002; Bonnet, 2004; Jacoby, 2009)
Our analysis revealed that Class 1 integrons were common in E. coli isolates of river Yamuna (50%), more than those reported from strains isolated from Malaysia (21%) (Ghaderpour et al, 2015), France and Portugal (11%) (Laroche et al, 2009; Pereira et al, 2013), and Czechia (15%) (Dolejská et al, 2009)
The genetic environment of blaTEM-1, blaCTX-M-15, and blaCMY-42 in E. coli strains present in the urban aquatic environment of India has been reported for the first time
Summary
Extensive use of third-generation cephalosporins for humans and veterinary purposes has led to an increased incidence and distribution of extended spectrum β-lactamases (ESBLs) and AmpC in bacteria (Bradford, 2001; Philippon et al, 2002; Bonnet, 2004; Jacoby, 2009). The frequency of genetic mutations is normally low in nature (Zimmer et al, 1963; Gassmann et al, 2000), acquisition of ARGs through horizontal gene transfer (HGT) has been regarded as an important means for the wide spread antimicrobial resistance It involves mobile genetic elements such as plasmids, transposons, and integrons. The presence of antimicrobial resistance and their genes in E. coli in aquatic environments has been reported by many investigators (Koczura et al, 2013; Pereira et al, 2013) This is quite alarming, because such genes (ESBLs and AmpC) can be transferred among bacterial species with the help of mobile genetic elements, viz. ISEcp was reportedly associated with blaCTX-M-15 and blaCMY-42. orf477 and blc-sugE were present downstream of blaCTX-M-15 and blaCMY-42, respectively (Bailey et al, 2011; Dhanji et al, 2011; Hentschke et al, 2011; Mata et al, 2012)
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