Application of bacteriophages to reduce Salmonella attachment and biofilms on hard surfaces

This study evaluated the effectiveness of bacteriophage treatment for reducing Salmonella attachment and biofilms on hard surfaces. Bacteriophages (n = 6) were selected for bacteriophage treatment based on host ranges against Salmonella isolates (n = 10) obtained from rendering plants. The effectiveness of bacteriophage treatment (104-108 PFU/mL) was initially evaluated against strong Salmonella biofilm formers in 96-well microplate. Then, the bacteriophage treatment (109 PFU/mL) was applied for 7 d to reduce Salmonella attached to the stainless steel surfaces under laboratory and greenhouse conditions. The inhibition of biofilm formation and reduction of pre-formed biofilm in 96-well microplate with bacteriophage treatment reached up to 90 and 66%, respectively. Under laboratory conditions, bacteriophage treatment reduced up to 2.9 and 3.0 log CFU/cm2 of attachment and slightly formed biofilm of selected top 10 Salmonella strains and an avirulent Salmonella Typhimurium strain 8243, respectively, as compared with reductions of 3.4, 1.4, and 3.0 log CFU/cm2 of S. Typhimurium strain 8243 in summer, fall/winter, and spring seasons under greenhouse conditions, respectively. Clearly, bacteriophages were effective on reducing Salmonella attachment and biofilms formed on hard surfaces under both laboratory and greenhouse conditions. The use of bacteriophages on hard surfaces may have merits in reducing the likelihood of finished rendered products being recontaminated with Salmonella in rendering plants.