Enterococci in river Ganga surface waters: Propensity of species distribution, dissemination of antimicrobial-resistance and virulence-markers among species along landscape

Enterococci density (χ2: 1900, df: 1; p < 0.0001) increased from up-to-down gradient sites in the landscape. Species diversity exhibit significant (χ2: 100.4, df: 20; p < 0.0001) and progressive distribution of E. faecalis, E. faecium, E. durans and E. hirae down the gradient. Statistically discernible (p: 0.0156 – < 0.0001) background pool of resistance and virulence was observed among different Enterococcus spp. recovered from five sites in the up-to-down gradient landscape. A significant correlation was observed in the distribution of multiple-antimicrobial-resistance (viz., erythromycin-rifampicin-gentamicin-methicillin and vancomycin-gentamicin-streptomycin; rs: 0.9747; p: 0.0083) and multiple-virulence-markers (viz., gelE+esp+; rs: 0.9747; p: 0.0083; gelE+efaA+; rs: 0.8944; p: 0.0417) among different Enterococcus spp.Our observations show prevalence of multiple-antimicrobial-resistance as well as multiple-virulence traits among different Enterococcus spp. The observed high background pool of resistance and virulence in enterococci in river waters of populous countries has the potential to disseminate more alarming antimicrobial-resistant pathogenic bacteria of same or other lineage in the environment. Therefore, the presence of elevated levels of virulent enterococci with emerging vancomycin resistance in surface waters poses serious health risk in developing countries like India.Enterococci, commensal organisms in gastrointestinal tract of human and animals have emerged as a leading cause of nosocomial infections [1]. Enterococcus faecalis (E. faecalis) and E. faecium are the two major pathogenic species in human, with sporadic infections caused by E. durans, E. hirae and other enterococci [2]. The presence of enterococci as an indicator of fecal contamination has been used in management of recreational water quality standards as it correlates best with the incidence of swimming-related illnesses [3,4]. Various virulence traits such as gelatinase (gelE), ente