Campylobacter species, particularly C. jejuni and C. coli, are among the leading causes of bacterial gastroenteritis worldwide, transmitted through contaminated food, water, and environmental reservoirs [1]. CRISPR-Cas systems play a crucial role in bacterial immunity against mobile genetic elements (MGEs,[2]) and serve as valuable tools for strain typing and source attribution [3]. This study explores the diversity and characteristics of CRISPR-Cas systems across a dataset of 2616 Campylobacter genomes from various sources, including shellfish and surface water [4,5].

Our analysis revealed that 1530 out of 2616 genomes (58.5%) harbored at least one CRISPR array, with significant differences between species. C. jejuni exhibited the highest prevalence of CRISPR-Cas systems, followed by C. coli, while most C. lari isolates lacked CRISPR arrays, and displayed a distinct distribution of CRISPR types. A total of 1530 CRISPR arrays were identified, with many strains carrying two or more arrays. Type II CRISPR-Cas systems predominated in C. jejuni and C. coli. Interestingly, Type III CRISPR-Cas systems were as prevalent as Type II in C. lari, suggesting functional diversity.

A comparative analysis of CRISPR array composition identified 909 unique arrays and 3169 unique spacers, suggesting high variability. Spacer analysis indicated frequent matches with a few phages, highlighting inter-species encounters. Our findings provide novel insights into the diversity of Campylobacter CRISPR-Cas systems and their potential application in source tracking, particularly within a One Health framework.

1. Caron, G.; et al. 2021.

2. Barrangou, R.; et al, 2007.

3. Pearson, B.M.; et al 2015

4. Gourmelon, M.; et al 2022

5. Mulder, A.C.; et al 2020