Host clustering of Campylobacter species and enteric pathogens in a longitudinal cohort of infants, family members and livestock in rural Eastern Ethiopia
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Background
Livestock are recognized as major reservoirs for Campylobacter species and other enteric pathogens, posing infection risks to humans. High prevalence of Campylobacter during early childhood has been linked to environmental enteric dysfunction and stunting, particularly in low-resource settings.
Methods
A total of 280 samples from Campylobacter positive households with complete metadata were analyzed by shotgun metagenomic sequencing followed by bioinformatic analysis via the CZ-ID metagenomic pipeline (Illumina mNGS Pipeline v7.1). Further statistical analyses in JMP PRO 16 explored the microbiome, emphasizing Campylobacter and other enteric pathogens. Two-way hierarchical clustering and split k-mer analysis examined host structuring, patterns of co-infections and genetic relationships. Principal component analysis was used to characterize microbiome composition across the seven sample types.
Results
The study identified that microbiome composition was strongly host-driven, with more than 3844 genera detected, and two principal components explaining 62% of the total variation. Twenty-one dominant (based on relative abundance) Campylobacter species showed distinct clustering patterns for humans, ruminants, and broad hosts. The broad-host cluster included the most prevalent species, C . jejuni , C . concisus , and C . coli , present across sample types and a sub-cluster within C . jejuni involving humans, chickens, and ruminants. Campylobacter species from chickens showed strong positive correlations with mothers ( r = 0.76), siblings ( r = 0.61) and infants ( r = 0.54), while co-occurrence analysis found a higher likelihood (Pr > 0.5) of pairs such as C . jejuni with C . coli , C . concisus , and C . showae . Analysis of the top 50 most abundant microbial taxa showed a distinct cluster uniquely present in human stool and absent in all livestock. The study also found frequent co-occurrence of C . jejuni with other enteric pathogens such as Salmonella , and Shigella , particularly in human and chicken. Additionally, instances of Candidatus Campylobacter infans ( C . infans ) were identified co-occurring with Salmonella and Shigella species in stool samples from infants, mothers, and siblings.
Conclusions
A comprehensive analysis of Campylobacter diversity in humans and livestock in a low-resource setting revealed that infants can be exposed to multiple Campylobacter species early in life. C . jejuni is the dominant species with a propensity for co-occurrence with other notable enteric bacterial pathogens, including Salmonella, and Shigella , especially among infants.
