Effect of two lytic bacteriophages against multidrug-resistant and biofilm-forming Salmonella Gallinarum from poultry.

1. Salmonella Gallinarum (SG) infections cause fowl typhoid, which leads to important economic losses. Multidrug resistance (MDR) and the capacity for bacteria to form biofilms could play an important role in the persistence of SG in poultry flocks resulting in intermittent disease outbreaks. The aim of the following study was to assess the lytic activity of two new bacteriophages (Salmonella phages UPF_BP1 and UPF_BP2) against MDR and biofilm-forming SG. 2. Forty-six strains of SG, isolated in 2015, were characterised by antimicrobial resistance, biofilm formation profiles and susceptibility to two new bacteriophages. 3. Of these strains, 24% were multidrug resistant and more than 80% formed biofilm, with no statistical difference between incubation temperatures (42°C or 22°C). With regard to the lytic activity of the phages, 85% of strains were susceptible to at least one phage. Of these, 74% were lysed by both phages, including MDR and biofilm producing strains. 4. The use of salmonella phages UPF_BP1 and UPF_BP2 were shown to be promising alternatives for the biological control of fowl typhoid.