Isolation and genomic characterization of novel Escherichia phage with potential to control multidrug resistant extended-spectrum βeta-lactamase-producing Escherichia coli.

Extended-spectrum beta-lactamase producing Escherichia coli are one of the most challenging causative agents of bovine mastitis. The emergence of multidrug resistance in ESBL-producing E. coli impedes antibiotic treatment and demands the need for alternative approaches such as phage therapy. In this study, a novel Escherichia phage belonging to Myoviridae family was isolated against multidrug resistant ESBL-producing E. coli. A total of 20 ESBL-producing E. coli were isolated from 84 clinical bovine mastitis milk samples. The 85% of the isolates were phenotypically confirmed as multidrug resistant and 45% of them were carrying antibiotic resistance genes against three or more antibiotics. Phage 92CQ was isolated against multidrug resistant ESBL-producing E. coli 92CQ. The isolated lytic Phage 92CQ displayed a broad host range, large burst size of 150 pfu/cell and short latent period of 30 min. Phage 92CQ was stable in the temperature range of 4°C-50 °C and showed effective lytic activity in the pH range of 5-11. Whole genome sequence analysis identified Phage 92CQ of 129812 bp, with 250 coding sequences, and 16 tRNAs. The lysis spanin complex composed of o-spanin gene embedded within i-spanin was identified in Phage 92CQ. The phylogenetic analysis showed a discrete categorisation of Phage 92CQ as a novel species within genus Justusliebigvirus. These results indicated the absence of antibiotic resistance, virulence and toxic genes in isolated phage with an effective reduction of multidrug resistant E. coli. The study presents Phage 92CQ as a potential candidate for development as a therapeutic agent with additional in-vivo and ex-vivo studies.