Isolation and characterization of phages that can be used in inhibition of lactococcus garvieae by phage therapy method in foods

Lactococcus garvieae is a fish pathogen that can cause various infectious diseases in humans, animals, and fish. It is particularly problematic in aquaculture, leading to significant economic losses. This bacterium can be found in environments such as freshwater, seawater, soil, and plant surfaces. While various methods, such as heat treatment and chemicals, are used to inhibit pathogens in food, these methods have their drawbacks. In contrast, bacteriophages, which have been considered as promising antimicrobial agents for the elimination of pathogens in recent years, offer several advantages. This study evaluated the effectiveness of a phage cocktail composed of lytic bacteriophages specific to L. garvieae on a water sample. For this purpose, 29 phages effective against L. garvieae were isolated from 24 raw milk samples collected from different regions of Bolu province, as well as 1 sewage water sample. After isolating and purifying these phages, their titers reached 108 PFU/mL, and their DNA was isolated and RFLP profiles were determined. Based on the restriction profiles, the phages were divided into three groups, and the phages with the highest titers, namely 12S4-2, 15S3-2, and 15S21-2, were selected and characterized. The characterization of these phages involved determining their infection multiplicities, adsorption rates, host ranges, latent periods, and burst sizes. A phage cocktail was prepared using the characterized phages 12S4-2, 15S3-2, and 15S21-2, and its effectiveness on L. garvieae in the water sample was observed. The results showed that the phage cocktail completely eliminated L. garvieae strains at MOI (Multiplicity of Infection) values of 0.1 and 10. This results indicate that the phage cocktail effectively reduced the presence of L. garvieae in the water sample and could potentially be used for controlling the pathogen.