Reduction of Salmonella contamination on the surface of chicken skin using bacteriophage

Background Enteric infections caused bySalmonellaspp. remain a major public health burden worldwide. Chickens are known to be a major reservoir for this zoonotic pathogen. The presence ofSalmonellain poultry farms and abattoirs is associated with financial costs of treatment and a serious risk to human health. The use of bacteriophages as a biocontrol is one possible intervention by whichSalmonellacolonization of chickens could be reduced. In a prior study, phages E phi 151 and T phi 7 significantly reduced broiler chicken caecal colonization byS.Enteritidis andS.Typhimurium respectively. Methods Salmonella-free Ross broiler chickens were orally infected withS.Enteritidis P125109 orS.Typhimurium 4/74. After 7 days of infection, the animals were euthanased, and 25cm(2)sections of skin were collected. The skin samples were sprayed with a phage suspension of either E phi 151 (S.Enteritidis), T phi 7 phage suspension (S.Typhimurium) or SM buffer (Control). After incubation, the number of survivingSalmonellas was determined by direct plating and Most Probable Number (MPN). To determine the rate of reduction ofSalmonellanumbers on the skin surface, a bioluminescentS. Typhimurium DT104 strain was cultured, spread on sections of chicken breast skin, and after spraying with a T phi 11 phage suspension, skin samples were monitored using photon counting for up to 24 h. Results The median levels ofSalmonellareduction following phage treatment were 1.38 log(10)MPN (Enteritidis) and 1.83 log(10)MPN (Typhimurium) per skin section. Treatment reductions were significant when compared withSalmonellarecovery from control skin sections treated with buffer (p < 0.0001). Additionally, significant reduction in light intensity was observed within 1 min of phage T phi 11 spraying onto the skin contaminated with a bioluminescentSalmonellarecombinant strain, compared with buffer-treated controls (p < 0.01), implying that some lysis ofSalmonellawas occurring on the skin surface. Conclusions The results of this study suggest that phages may be used on the surface of chicken skin as biocontrol agents againstSalmonellainfected broiler chicken carcasses. The rate of bioluminescence reduction shown by the recombinantSalmonellastrain used supported the hypothesis that at least some of the reduction observed was due to lysis occurred on the skin surface.