Genomic and clinical characteristics of campylobacteriosis in Australia

Abstract

Campylobacter spp. 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 422 C. jejuni and 84 C. coli case 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 65 C. jejuni and 21 C. coli sequence types. Antimicrobial resistance genes were detected in 20.4 % of isolates, but multidrug resistance was rare (0.04 %). Key virulence genes such as cdtABC (C. jejuni) and cadF were prevalent (>90 % presence) but did not correlate with disease severity or hospitalisation. However, certain genes (e.g. fliK, Cj1136, and Cj1138) appeared to distinguish human C. jejuni cases 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 human C. jejuni cases from food source isolates. Host factors like age and comorbidities have a greater influence on health outcomes than virulence factors.

Keywords: Campylobacter; antimicrobial resistance; clinical outcomes; severity; virulence; whole genome sequencing.

Fig. 1.

(a) Symptom profiles of Australian campylobacteriosis cases (muscle and body aches, nausea, and stomach cramps), 2018–2019. (b) Symptom profiles of Australian campylobacteriosis cases (blood in stool, fever, headache, and vomiting), 2018–2019. (c) Course of disease characteristics of Australian campylobacteriosis cases (hospitalisation, hospitalisation ≥3 days, length of illness ≥7 days), 2018–2019. The solid lines indicate estimated prevalence from a univariable generalised additive model with a logit link. Shading around each line represents the 95 % confidence interval for the prevalence estimate.

Fig. 2.

Distribution of modified Vesikari scoring system scores for 571 campylobacteriosis cases in Australia, 2018–2019. Bars represent the percentage of cases reporting the corresponding Vesikari score. Error bars are calculated from binomial confidence intervals using the Pearson-Klopper exact method. Counts are provided above the bar for each Vesikari score.

Fig. 3.

Distribution of modified Vesikari scoring system scores by age for 571 campylobacteriosis cases in Australia, 2018–2019. The solid line indicates the estimated score from a generalised additive model with a logit link. Shading around the line represents the 95 % confidence interval for the score estimate.

Fig. 4.

Genotypic antimicrobial resistance profiles of 506 Campylobacter isolates for ampicillin (AMP), ciprofloxacin (CIP), erythromycin (ERY), gentamicin (GEN), and tetracycline (TET). Isolates were classified as susceptible if they did not possess a known resistance gene or mutation (n=403). The number of isolates possessing each resistance profile is noted above the respective bar. Error bars are calculated from binomial confidence intervals using the Pearson-Klopper exact method.