Detection of the same type of Campylobacter in several countries has challenged previous beliefs that it is associated with unrelated infections.
Researchers reported the previously unrecognized circulation of a multidrug-resistant Campylobacter coli sequence type across Europe during 2018 to 2025. However, they said the lack of epidemiological data means transmission routes and outbreaks cannot be confirmed.
Whole genome sequencing (WGS) of 217 isolates from nine countries of human, animal, food, and environmental sources identified cross-border clusters.
Campylobacteriosis cases are primarily caused by Campylobacter jejuni followed by Campylobacter coli. Poultry is the main reservoir. Infections have been considered sporadic but WGS–based surveillance has demonstrated that many cases occur as genetically related clusters.
Scientists said the multidrug-resistant Campylobacter coli sequence type (ST) 10042 was associated with a peak of infections in Portugal and has been detected in Germany, Luxembourg, France, Ireland, Denmark, Netherlands, the United Kingdom, and Spain.
Multi-country analysis
Given the increase in Campylobacter coli in Portugal in 2022, driven by ST10042, researchers conducted an extended investigation. Findings were published in Emerging Infectious Diseases.
Of the 217 isolates, most were from humans and Portugal contributed the largest number, followed by Germany and Luxembourg. Portugal, Luxembourg, the Netherlands and Ireland also had animal/food isolates, but environmental isolates were detected only in Portugal and Luxembourg.
Of the 30 animal and human food-derived isolates, 25 were from poultry. Food isolates were recovered from raw chicken and turkey meat in Portugal, and from chicken-based prepared dishes in Luxembourg.
The 104 Portuguese isolates from 2020 to 2025 consisted of one main cluster of 28 isolates and 15 smaller clusters of 2 to 4 isolates while the others were sporadic. The main cluster had 20 human isolates from 2021 to 2024, and eight nonhuman isolates from chicken, turkey or cattle collected in 2021 to 2022, and three poultry meat isolates from 2021, 2023, and 2024.
One cluster from Ireland, which included chicken and human isolates from 2021 and 2022, was consistent with an outbreak, possibly linked to chicken contamination.
Despite low international reports, the strain was found in databases across Europe, forming distinct genetic clusters across countries and sectors. The lack of detailed epidemiological metadata means transmission routes and outbreak causality remain unknown.
“These findings demonstrate that Campylobacter coli infections can involve sustained international transmission rather than sporadic cases and highlight the need for coordinated, cross-sector genomic surveillance to detect emerging antimicrobial-resistant lineages,” said scientists.
