Bio-control Of Salmonella Enteritidis In Food Using Biocteriophages

Salmonella, especially salmonella enteritidis has been the most common enteric and food-borne pathogenic bacteria worldwide. The abuse of antibiotics makes the phenomenon of salmonella resistance to antibiotics escalating. Some physical treatments may be restricted due to the problems of deterioration of the organoleptic properties may come after these treatments. In this study, two phages were isolated from environmental sewage samples, and then the characterization, biological properties and control of salmonella enteritidis in food were studied. The main research work and results were listed below.1. The separation and biological characteristics research of salmonella phagesTwo virulent phages were isolated from environmental sewage samples. As the using host strains were CVCC2184and ATCC13076, the two phages were named after vB_SenM-PC2184(PC2184in short) and vB_SenM-PA13076(PA13076in short) respectively. Host range studies showed that they were broad-spectrum phages. The electron microscope showed the two phages were assigned to the family Myoviridae. The biological properties of them were similar with that of most other phages, like good thermal stability but wider pH stability, especially PA13076, showed some basophilic property. The optimal multiplicity of infection (MOI) of PC218C and PA13076were10:1and1:100respectively and PA13076had the shorter latent period and longer burst period.2. The study of the lysis characteristic of salmonella phagesThe lysis characteristics of phages in vitro showed that the higher MOI was the better degerming effect observed, and the bactericidal ability of PC2184was stronger than PA13076. The biological control of salmonella enteritidis in chicken, milk and lettuce by two phages was analyzed. In general, the protection effect of phage against the host bacteria at4℃was better than that at25℃(opposite result was observed in the lettuce because of the effect of water activity), and the phage cocktails showed better than application a phage alone. The degerming effect in milk was better than that in chicken because of the better mutual contaction between the phage and bacteria, and a better degerming effect in lettuce was also observed because of the smooth surface of lettuce and the lack of nutrient on it. The stability of phage on the three food samples was good, especially at4℃, ant the stability in milk is the best. 3. The influence of salmonella phages application on food quality and safetyThe qualities of the three different food samples after the treatment of phage were analyzed. The addition of phage had insignificant(p<0.05) effect on the color of lettuce, the pH value, the turbidity and color of milk, and the pH value, color and the original microbial community composition of chicken, thus the normal sensory and intrinsic quality of them was guaranteed.The biological control effect of salmonella enteritidis in food by phage PC2184and PA13076were great, and they may be a promising green natural food antimicrobial agent in the future.