Abstract
A major bottleneck in understanding zoonotic pathogens has been the analysis of pathogen co-infection dynamics. We have addressed this challenge using a novel direct sequencing approach for pathogen quantification in mixed infections. The major zoonotic food-borne pathogen Campylobacter jejuni, with an important reservoir in the gastrointestinal (GI) tract of chickens, was used as a model. We investigated the co-colonisation dynamics of seven C. jejuni strains in a chicken GI infection trial. The seven strains were isolated from an epidemiological study showing multiple strain infections at the farm level. We analysed time-series data, following the Campylobacter colonisation, as well as the dominant background flora of chickens. Data were collected from the infection at day 16 until the last sampling point at day 36. Chickens with two different background floras were studied, mature (treated with Broilact, which is a product consisting of bacteria from the intestinal flora of healthy hens) and spontaneous. The two treatments resulted in completely different background floras, yet similar Campylobacter colonisation patterns were detected in both groups. This suggests that it is the chicken host and not the background flora that is important in determining the Campylobacter colonisation pattern. Our results showed that mainly two of the seven C. jejuni strains dominated the Campylobacter flora in the chickens, with a shift of the dominating strain during the infection period. We propose a model in which multiple C. jejuni strains can colonise a single host, with the dominant strains being replaced as a consequence of strain-specific immune responses. This model represents a new understanding of C. jejuni epidemiology, with future implications for the development of novel intervention strategies.
Highlights
Understanding the ecology of zoonotic pathogens in the animal host is crucial for controlling infections in humans [1,2]
Field Data We found C. jejuni–positive chickens in three out of four farms using real-time PCR quantification
The number of C. jejuni– positive samples measured with real-time PCR was 53% at farm A, 38% at farm C, and 18% at farm D
Summary
Understanding the ecology of zoonotic pathogens in the animal host is crucial for controlling infections in humans [1,2]. With respect to within-host dynamics of pathogens One reason for this is the lack of experimental models addressing the effect of coinfections on pathogen colonisation. Multiple C. jejuni genotypes have been found in the GI tracts of individual chickens and within commercial broiler flocks [8,9,10,11,12,13]. The effects of co-infection dynamics and multiple strain infections, have not yet been described This knowledge is important for our understanding of the epidemiology of Campylobacter, and for the development of intervention strategies that can prevent C. jejuni from entering the food chain
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