Differentiating Enterococcus lineages in combined sewer overflow and potable water combating to hospital acquired high-level β-lactam resistance

Abstract

Understanding the sewage borne transmission pathway of hospital-associated enterococci can provide an insight for developing effective strategies to reduce the spread of nosocomial pathogens and illnesses in low- and middle-income countries. This research investigated the hospital borne enterococcal lineages in combined sewage overflowed (CSO) onto the streets and contaminating the freshwater, considered as an environmental challenge. The Enterococcus faecium and E. faecalis were heavily resistant to multiple β-lactams including, amino penicillins, cephalosporins (1st to 4th generation), carbapenems and aminoglycoside. Enterococcus species obtained from CSO exhibits resistance plasticity, which is correlated with varied ampicillin MICs (64 to ≥ 2048 μg ml−1), polymorphism in php4 and pbp5 genes and repetitive BOX-DNA. The quantified enterococcal densities in drinking water (i.e. 1.5 × 106 CFUs ml−1) were far beyond to the permissible limit defined by world health organization, and European food safety authority. The CSO and clinical species harbored IS16 element, clyA, esp, efaAfm, efaAfs, ace, and conjugative plasmids readily differentiated with waterborne and commensal strains might have been developed during niche adoption and broad spectral antibacterial activities. The bacteriocinogenic enterococcal groups in combined sewage were avirulent, susceptible to ampicillin and produced multiple enterocins (entA, entB, entP, entL, entL50, ent1071, ent1097, entSEK4). The enterocinogenic E. faecium showed natural abundance in CSO restrained the growth of six Enterococcus species (ATCC), β-lactam resistant enterococci of clinical and sewage origin, Listeria monocytogenes ATCC 13932, and Micrococcus leuteus ATCC 10240. Furthermore, enterocinogenic activities led to in-vitro dysbiosis of human microbiota. In conclusion, constant monitoring of sewage spills near residential areas essentially involved the enterococci (fecal and resistome indicator) and proper disposal of hospital waste prior to draining into community sewage and wastewater treatment plants is highly recommended.