USING LYTIC PHAGES TO REDUCE THE NUMBER OF SALMONELLA RODS IN PLANT FOOD MATRIX

Abstract

The object of the research study was to isolate bacteriophages from municipal wastewater and to determine the effectiveness of using them as a means to eliminate some selected Salmonella serovars from minimally processed food. Radish sprouts were a vegetable food matrix. Four bacteriophages specific against bacteria of the Salmonella genus were isolated. Their lytic activity was determined, as well as morphology using Transmission Electron Microscopy (TEM) and tolerance to selected environmental factors (temperature and pH). A prepared phage cocktail was applied to the radish sprouts previously infected with bacteria of the Salmonella genus using a spraying method and an absorbent insert. All the phages isolated effectively shortened the logarithmic growth phase of the strains tested. Those isolated phages were characterised by a complex structure. Based on the morphological analysis, they were classified as a Caudovirales order. The sensitivity of phages to environmental factors is an individual feature, and when designing a bacteriophage preparation, there should be selected phages with stable features and a wide range of tolerance to external factors. It was shown that the temperature had a stronger effect on the inhibition of lytic activity of the phages tested than the active acidity of the environment. Compared to the control samples, the highest reduction of Salmonella rods, at a level of 99 %, was achieved when using an absorbent pad containing the phage cocktail. The research study confirms the effectiveness of phages in ensuring the microbiological safety of minimally processed food. Although there are no EU legal rules ref. to lytic bacteriophages-based prepara-tions, in the future they may become one of the biological methods to improve the microbiological safety of minimally processed foods. They can also be an effective disinfectant designed to clean production equipment.