Campylobacter species remain the leading bacterial cause of foodborne gastroenteritis in Western countries. Since 2005, campylobacteriosis has been the most frequently reported foodborne zoonosis in the European Union; 168,396 human cases were reported in 2024. Infections affect all ages and are most severe in young children, the elderly, and immunocompromised persons, manifesting typically with bloody or watery diarrhea, abdominal cramps, fever, vomiting, and nausea. Severe or prolonged illness can lead to complications such as bacteremia that occasionally require hospitalization or result in death. Antimicrobial therapy is reserved for severe infections, raising concerns about Campylobacter antimicrobial resistance (AMR), particularly to fluoroquinolones, macrolides, and carbapenems.
Approximately 90% of human cases are caused by Campylobacter jejuni and ≈10% by Campylobacter coli. While poultry is the primary reservoir, livestock, wild and domestic animals, humans, and contaminated water or soil also contribute to transmission. Historically considered largely sporadic, recent whole-genome sequencing (WGS) surveillance has revealed that many cases cluster genetically, underscoring the value of genomic approaches for outbreak detection and source attribution.
The investigation took advantage of ongoing WGS-based surveillance coordinated by the Portuguese National Reference Laboratory for Gastrointestinal Infections (NRL-GI) at the National Institute of Health Doutor Ricardo Jorge. Since 2013 the NRL-GI has run sentinel laboratory–based surveillance of human campylobacteriosis across multiple geographic areas and private laboratory networks in mainland Portugal, with routine monthly isolate submission throughout the year. Systematic WGS was implemented from 2022 onward, achieving approximately 90% coverage for C. coli WGS and antimicrobial susceptibility testing.
Animal and food-chain surveillance was conducted by the National Institute for Agricultural and Veterinary Research, with livestock isolates collected at slaughter under the European monitoring framework. Additional environmental, animal, and food product isolates were obtained from collaborative projects, including retail poultry meat screening and targeted studies in dogs.
The study sample focused on C. coli ST10042 isolates identified since WGS implementation in Portugal (2022) and included retrospective sequencing of all C. coli isolates received during 2016–2021 that exhibited the conserved ST10042 AMR phenotype. ST10042 had been underrecognized in public databases prior to these surveillance efforts.
Whole-genome sequencing of 217 isolates from nine countries spanning human, animal, food, and environmental sources was used to characterize the ST10042 lineage. Core-genome multilocus sequence typing and high-resolution WGS approaches allowed identification of cross-border clusters and the assessment of population structure.
Analyses showed a large lineage linking primarily Portugal and Luxembourg, with additional related isolates reported from Germany, Ireland, Spain, and the United Kingdom. Genomic data indicate ongoing clonal expansion accompanied by increasing diversification over time, consistent with sustained transmission rather than isolated, sporadic events.
Specific phylogenetic metrics, mutation rates, and detailed cluster size distributions were not reported in the excerpt provided.
Isolates displayed a conserved multidrug-resistant phenotype, characterized by resistance to fluoroquinolones, tetracyclines, and β-lactams. The study also observed reduced susceptibility to carbapenems among isolates.
Genetic markers linked to the observed AMR phenotype included the GyrA Thr86Ile substitution (fluoroquinolone resistance) and the presence of tet(O/32/O) and tet(O) genes (tetracycline resistance). β-lactam resistance was associated with bla_OXA-61 promoter variants. Variation in the porA gene, which encodes the major Campylobacter outer-membrane porin, was associated with variable susceptibility to amoxicillin/clavulanic acid and ertapenem, supporting a role for porA allelic differences in modulating β-lactam and carbapenem influx through altered membrane permeability.
Further functional validation of these genetic associations and full AST breakpoints or MIC distributions were not described in the provided text.
The ST10042 lineage was detected across multiple sectors—human clinical cases, animals, food products, and environmental samples—demonstrating a multisectoral distribution. Cross-border genomic clusters were identified, with a prominent lineage linking Portugal and Luxembourg and additional spread to Germany, Ireland, Spain, and the United Kingdom. The multisector and multinational detection underscores zoonotic and environmental pathways that can sustain and disseminate resistant C. coli lineages across countries.
Details on temporal trends by country, specific source attribution proportions, and travel- or trade-related transmission pathways were not fully reported in the excerpt.
The identification of a sustained, multidrug-resistant C. coli ST10042 lineage across Europe highlights two main public health concerns: first, that some campylobacteriosis cases previously considered sporadic may reflect ongoing international transmission networks; and second, that emerging multidrug-resistant lineages can limit therapeutic options for severe infections.
The authors emphasize the value of coordinated, cross-sector genomic surveillance—integrating human, veterinary, food-chain, and environmental sampling—to detect and monitor emerging AMR lineages. High-coverage WGS and systematic retrospective sequencing allowed recognition of this lineage after it had been underrecognized in public databases, illustrating the importance of comprehensive genomic datasets for timely detection.
The provided excerpt includes the abstract, background, and partial methods but does not contain full methodological detail, complete results, or full discussion content. Specific counts of isolates by year, country-level timelines, full phylogenetic trees, statistical support values, and detailed antimicrobial susceptibility testing data (MIC ranges, breakpoints) were not present in the text excerpt. Where such specifics are required for operational decision-making or deeper epidemiologic interpretation, the full article and supplementary materials should be consulted.
Overall, the evidence presented supports clonal expansion and multisectoral international circulation of a multidrug-resistant Campylobacter coli ST10042 lineage in Europe during 2018–2025 and reinforces the need for integrated genomic surveillance to inform prevention and control strategies.