Sex pilus specific bacteriophage to drive bacterial population towards antibiotic sensitivity.

Antimicrobial resistance (AMR) is now a major global problem for treatment of infectious diseases resulting largely from overuse of antimicrobials in human and veterinary medicine and livestock production. Alternatives to antimicrobials are required urgently and this can include the use of bacteriophages (phage). Most bacterial AMR is encoded by large conjugative plasmids, which spread readily through bacterial populations. In this present study, we show that a sex pilus-specific phage is able to kill AMR Escherichia coli in vitro by targeting the sex pili but can also select for extensive AMR plasmid loss in phage-resistant mutants that arise during treatment. Massive plasmid loss occurred in vivo in phage-treated chickens which had been infected with an AMR Salmonella Enteritidis strain. Bacteriophage use can thus be considered not only as an antibacterial but to drive bacterial evolution towards a reduction in AMR.