Campylobacter Phage Isolation and Characterization: What We Have Learned So Far

Abstract

Lytic Campylobacter phages, which can be used to combat this pathogen in animals and on food products, have been studied for more than 30 years. Though, due to some peculiarities of the phages, which hampered their isolation and particularly their molecular analysis for a long time, progress in this research field was rather slow. Meanwhile, the situation has changed and much more is known about the biology and genetics of those phages. In this article, we address specific issues that should be considered when Campylobacter phages are studied, starting with the isolation and propagation of the phages and ending with a thorough characterization including whole-genome sequencing. The basis for advice and recommendations given here is a careful review of the scientific literature and experiences that we have had ourselves with Campylobacter phages.

Application of Campylobacter jejuni Phages: Challenges and Perspectives

“…For wider activity and greater potency against C. jejuni, it is advisable that polyphage applications (phage cocktails) targeting this pathogen be comprised of the representatives of both CPS-specific and flagellotropic phages or to administer the phages from these groups successively [37,88]. Prevention of recycling of phages reduces resistance rates in a farm environment, therefore conducting phage therapy in birds 1-2 days prior to slaughter could help to avoid resistance [15].…”

“…Lytic Campylobacter phages are divided into three groups according to the size of their genome: group I contains relatively rare phages with large genomes (approx. 320-425 kbp), while groups II and III include most Campylobacter phages isolated and characterized to date [37]. These are all distantly related to T4 bacteriophages and have smaller genomes: 175 to 183 kbp (group II) and 131 to 135 kbp (group III).…”

“…Group II and III Campylophages exhibit resistance to many restriction endonucleases. These phages are characterized with great similarities within each group but differences between the groups [37,38]. Group II Campylophages are often specific to both C. jejuni and C. coli, while group III phages demonstrate specificity exclusively to C. jejuni and have stronger lytic activity [37].…”

“…The latest phage classification scheme, which is based on whole genome sequencing and protein homology, puts group II and III phages into the Eucampyvirinae sub-family of myoviridae as "CP220-like viruses" and "CP8-unalike viruses"/"CP8 virus" [37][38][39]. Sørensen and colleagues showed, with some exceptions, the connection between receptor dependency and grouping of C. jejuni phages.…”

“…However, it is essential to use a broad range of strains for the selection and isolation of Campylobacter phages, because the primary phage isolation strain largely determines both phage type (CP81 or CP220) and receptors (CPS or flagella), as demonstrated by Sørensen and colleagues [40]. The use of control C. jejuni strains, also known as phage propagating strains (NCTC 12662 (PT14), NCTC 12660, NCTC 12661 and NCTC 12664), susceptible to a wide range of phages may have resulted in biased selection of the latter [37,71]. For example, Sørensen and colleagues used C. jejuni strains with different CPS profiles to isolate bacteriophages from free-range poultry samples.…”