Genomic and clinical characteristics of campylobacteriosis in Australia
Authors: Cribb Danielle M , Moffatt Cameron RM , Wallace Rhiannon L , McLure Angus T , Bulach Dieter , Jennison Amy V , French Nigel , Valcanis Mary , Glass Kathryn , Kirk Martyn D 
Published: October 2023

AbstractCampylobacterspp. are a common cause of bacterial gastroenteritis in Australia, primarily acquired from contaminated meat. We investigated the relationship between genomic virulence characteristics and the severity of campylobacteriosis, hospitalisation, and other host factors.We recruited 571 campylobacteriosis cases from three Australian states and territories (2018–2019). We collected demographic, health status, risk factors, and self-reported disease data. We whole genome sequenced 422C. jejuniand 84C. colicase isolates along with 616 retail meat isolates. We classified case illness severity using a modified Vesikari scoring system, performed phylogenomic analysis, and explored risk factors for hospitalisation and illness severity.On average, cases experienced a 7.5-day diarrhoeal illness with additional symptoms including stomach cramps (87.1%), fever (75.6%), and nausea (72.0%). Cases aged ≥75 years had milder symptoms, lower Vesikari scores, and higher odds of hospitalisation compared to younger cases. Chronic gastrointestinal illnesses also increased odds of hospitalisation. We observed significant diversity among isolates, with 65C. jejuniand 21C. colisequence types. Antimicrobial resistance genes were detected in 20.4% of isolates, but multidrug resistance was rare (0.04%). Key virulence genes such ascdtABC(C. jejuni) andcadFwere prevalent (>90% presence) but did not correlate with disease severity or hospitalisation. However, certain genes appeared to distinguish humanC. jejunicases from food source isolates.Campylobacteriosis generally presents similarly across cases, though some are more severe. Genotypic virulence factors identified in the literature to-date do not predict disease severity but may differentiate humanC. jejunicases from food source isolates. Host factors like age and comorbidities have a greater influence on health outcomes than virulence factors.Author summaryThis study focused onCampylobacter,a common cause of gastroenteritis in Australia. We explored the relationship betweenCampylobacter’sgenomic characteristics and disease severity, hospitalisation, and host-related factors.In 2018 – 2019, we collected data from 571 campylobacteriosis cases from Eastern Australia, focusing on demographics, health status, risk factors, and self-reported symptoms. We sequenced 422C. jejuniand 84C. colicase isolates and 616 retail meat isolates. We used a modified Vesikari scoring system to assess illness severity, performed phylogenomic analysis, and explored hospitalisation and severity risk factors.Cases experienced an average 7.5-day period of diarrhoea with additional symptoms including stomach cramps, fever, and nausea. Older individuals (75+ years) had milder symptoms but a higher chance of hospitalisation. Those with chromic gastrointestinal conditions faced increased hospitalisation odds. Case isolates showed considerable diversity. Antimicrobial resistance genes were detected in some isolates, but multidrug resistance was rare. Virulence genes did not predict severity or hospitalisation, but some genes did differentiate between case and food sourceC. jejuniisolates. Host-related factors including age and comorbidities are more important in determining health outcomes.