The newly isolated lytic bacteriophages st104a and st104b are highly virulent against Salmonella enterica.

Aims: To screen Irish faecal samples from a variety of sources with a view to isolating novel anti-Salmonella phages and to subsequently evaluate their lytic capability.

Methods And Results: Two novel anti-Salmonella phages st104a and st104b were isolated from a screening programme based on their lytic capability. The phages produced significantly larger plaques (2 mm) on the chosen indicator Salmonella enterica strain, DPC6046, when compared with the well-known control phage, Felix 01 (0.5 mm). Both phages st104a and st104b were found to have a broad host range within the Salm. enterica species. During in vitro trials, both phages (st104a and st104b) reduced Salm. enterica numbers more than 99% within 1 h. In vivo studies, involving the addition of the phage to porcine gastric juice (pH 2.5) demonstrated that phage st104a and phage Felix 01 were capable of surviving (10 and 30% survival respectively) the acidic conditions, unlike st104b, which was undetectable after 2 h exposure.

Conclusions: Two novel lytic anti-Salmonella phages were isolated and characterized.

Significance And Impact Of The Study: With the exception of phage Felix 01, there has been relatively little phage therapy work performed using lytic Salmonella phage. In this study, the lytic phages st104a and st104b were isolated as a result of a faecal screening programme. Subsequently, phage st104a was found to have potential for biocontrol of Salm. enterica numbers if administered orally to pigs given their survival in porcine gastric juice, whereas, phage st104b may have potential in reducing cell numbers if applied by alternative approaches.