Genomic surveillance identifies stable C. jejuni lineages causing disease in humans

Question: Campylobacter enteritis is a notifiable disease in Germany. More than 40,000 cases are reported annually. The majority of cases is caused by C. jejuni and is considered to be sporadic. In order to gain more insight into the population structure of clinical C. jejuni strains genomic surveillance was established in 2020. Here we describe major genomic lineages of C. jejuni, which play a central role in human disease.

Methods: Campylobacter spp. were cultivated on CCDA under microaerophilic conditions followed by PCR-based species determination. Whole genome sequencing was performed with Illumina NextSeq. Analysis of reads was conducted with Ridom SeqSphere+.

Results: Four years of surveillance data (2020-2024) reveal the existence of stable C. jejuni lineages as the cause of a significant amount of Campylobacter enteritis cases in Germany. To date, 14 lineages comprising approximately 850 (21%) isolates have been identified. This corresponds to approximately 8400 cases as only 4% of all notified cases are covered by the molecular surveillance program. The majority of isolates (124) belonged to complex type (CT) 2243. Case numbers peaked from February - April 2021 (36 cases) and December - February 2022 (35 cases). A smaller peak occurred in July 2023 (6 cases), indicating that this lineage is recurrent and stable over time. Another remarkable lineage is CT 2151 (ST-7355), which currently comprises 96 isolates, peaking from April – October 2022 (45 cases). This lineage has been associated with clinical cases in Denmark, Sweden and Luxembourg but has also been isolated from German poultry and poultry farms. Many of the lineages belong to CC ST-21 (6/14). Four of the six CC ST-21 lineages belong to ST-50. ST-50 has been described to occur worldwide and evolve regionally (Wallace et al. 2021). All major lineages identified so far have matching isolates from poultry origin.

Conclusion: Data from genomic surveillance points to the existence of internationally distributed recurring C. jejuni lineages causing the majority of Campylobacter enteritis cases in Germany. Therefore, an international one health approach is required for achieving reduction of cases.