Food-related factors influencing phage efficacy in reducing Campylobacter jejuni counts

Campylobacter jejuni is a global major foodborne pathogen and the leading cause for gastrointestinal infections in the European Union, often associated with the consumption of contaminated chicken meat. Physical and chemical decontamination measures can negatively affect the organoleptic properties of raw chicken meat while bacteriophages, as biological approach, can specifically combat pathogenic bacteria and have virtually no impact on the sensory attributes of the food matrix. However, their mode of action usually requires the growth of the target pathogen. This study aimed to systematically investigate the impact of the conditions prevailing in packaged raw chicken meat, compared to the host’s optimal growth conditions, on the antibacterial efficacy of a Campylobacter-specific phage. The flagellotropic bacteriophage B14 and its bacterial host Campylobacter jejuni PT14 were used to develop a liquid model system based on Mueller-Hinton broth, in which the parameters pH, atmosphere composition, temperature, and chicken meat juice concentration, as well as metal cations were adjusted and the effect on host growth as well as on the antibacterial efficacy of the phage was evaluated based on log ratios of C. jejuni PT14 counts. In general, the effectiveness of phage B14 treatment was significantly reduced when pH, atmosphere and temperature differed from optimum growth conditions of C. jejuni PT14 (pH 7 to 9; microaerobic; 42 ◦C). However, the influence on growth alone could not explain all effects on the antibacterial efficacy of the phage. The results show that conditions relevant for raw chicken meat storage are disadvantageous for the inactivation of C. jejuni PT14 by phage B14. These findings contribute to the understanding of the phage-host interaction and can support the optimization of the application concept of Campylobacter phages in poultry meat production.