Impact of effluent parameters and vancomycin concentration on vancomycin resistant Escherichia coli and its host specific bacteriophage lytic activity in hospital effluent

Vancomycin resistance in bacteria has been classified under high priority category by World Health Organization (WHO) and its presence in hospital effluent is reported to be increasing owing to excess antibiotics use. Among various strategies, bacteriophage has been recently considered as a promising biological agent for combating such antimicrobial resistant bacteria (ARB). However, the influence of effluent's properties on phage-ARB interaction in actual hospital effluent is not completely understood. The present works intends to study this influence of hospital effluent and its parameters on the interaction between vancomycin resistant E. coli (VRE) and its host specific bacteriophage. The isolated VRE was identified by 16S rRNA sequencing, matrix-assisted laser desorption/ionization-time of flight (MALDI - TOF) and whole genome sequencing. The infectivity of phage onto host bacteria was investigated using electron microscopic techniques, dynamic light scattering (DLS), spectrofluorophotometer and confirmed using double agar overlay method. The monovalency and polyvalency of isolated phage against various bacterial species were determined. The phage morphology was identical to T7 phage belonging to Podoviridae. The phage lysis was maximum at pH 7 (90.2%), 37 °C (91.6%) and vancomycin concentration of 50 μg/mL in both synthetic media (89.13%) and effluent (100%). At a maximum vancomycin concentration of 100 μg/mL, decrease in Ca, K, Mg and P (up to 19.70, 14.18, 28, and 15.82% respectively) concentration in effluent was observed due to phage infectivity when compared to control. The whole genome sequencing was performed and the bioinformatics analysis presented the role of mdfA gene encoding the efflux pump in causing vancomycin resistance in E. coli. It also depicted the presence of multiple genes responsible for mercury, cobalt, zinc and cadmium resistance in VRE. These results clearly indicate that bacteriophage mediated combating of VRE is possible in actual hospital effluent and can be used as one of the treatment methods.