Application of Campylobacter jejuni Phages: Challenges and Perspectives

Simple Summary Campylobacter jejuni is a zoonotic bacterial pathogen found in abundance, e.g., in raw poultry. C. jejuni is part of the avian gut microbiome, causing no harm to birds. When birds are slaughtered, the bacterium is released from the intestines and contaminates the meat. Cross-contaminated foods processed in parallel to the meat cause diarrhea in humans and in rare cases may cause post-infectious complications like arthritis and paralysis of peripheral nerves. Illnesses caused by C. jejuni have been on the rise in both developed and developing countries. At the same time, C. jejuni has acquired resistance to important antibiotics, which further complicates therapeutic approaches. To decrease the Campylobacter load on chicken carcasses, chemical or thermal treatment can be used. However, this may change the taste or affect the appearance of chicken meat. Alternative treatments include application of probiotics active against C. jejuni to live chickens or the use of bacteriophages (viruses killing bacteria) to decrease Campylobacter in the guts of live chickens prior to killing. This article discusses phage-based applications already in use against other bacterial pathogens and specifically highlights the challenges associated with the use of Campylobacter phages, emphasizing the ways to overcome these challenges based on the existing research. Bacteriophages (phages) are the most abundant and diverse biological entities in the biosphere. Due to the rise of multi-drug resistant bacterial strains during the past decade, phages are currently experiencing a renewed interest. Bacteriophages and their derivatives are being actively researched for their potential in the medical and biotechnology fields. Phage applications targeting pathogenic food-borne bacteria are currently being utilized for decontamination and therapy of live farm animals and as a biocontrol measure at the post-harvest level. For this indication, the United States Food and Drug Administration (FDA) has approved several phage products targeting Listeria sp., Salmonella sp. and Escherichia coli. Phage-based applications against Campylobacter jejuni could potentially be used in ways similar to those against Salmonella sp. and Listeria sp.; however, only very few Campylobacter phage products have been approved anywhere to date. The research on Campylobacter phages conducted thus far indicates that highly diverse subpopulations of C. jejuni as well as phage isolation and enrichment procedures influence the specificity and efficacy of Campylobacter phages. This review paper emphasizes conclusions from previous findings instrumental in facilitating isolation of Campylobacter phages and improving specificity and efficacy of the isolates.