Isolation, characterization, and dairy application of a novel bacteriophage fBSPA4 against Salmonella enterica

Non-typhoidal Salmonella (NTS), a zoonotic pathogen, is associated with food-borne illness in humans. Contaminated food such as milk and meat are major reservoir of Salmonella enterica, which is associated with salmonellosis in humans. In this work, we isolated and characterized a broad-spectrum lytic bacteriophage (fBSPA4) from chicken intestine that inhibits the growth of antibiotic resistance NTS isolates from several Indian poultry farms. fBSPA4 shows large burst size, a very short latent period, a strong tolerance to high temperatures (5-65 °C) and unnatural pH (3.0-11.0). Transmission electron microscopy (TEM) revealed that phage fBSPA4 possesses an icosahedral head (77 nm in diameter) and non-contractile tail (120 nm), characteristic of members of the class Caudoviricetes. Genome sequencing revealed a single contig of 87,179 base pairs with G + C content of 38.91%. The fBSPA4 has 123 codon-determining sequences (CDS) that are devoid of detrimental genes related to lysogeny, antibiotic resistance, virulence factors, or toxins. Further, ex vivo infection model showed that fBSPA4 significantly decreased Salmonella enterica levels in the buttermilk and yoghurt. In summary, this research highlights the potential use of fBSPA4 as a biocontrol agent to prevent contamination in milk products.