Competing isogenic Campylobacter strains exhibit variable population structures in vivo

Area of Science:

• Microbiology
• Animal Science
• Food Safety

Background:

• Campylobacter jejuni is a leading cause of human gastrointestinal illness, often transmitted through contaminated poultry.
• Understanding Campylobacter colonization in chickens is crucial for developing effective control strategies.
• Previous competition experiments assumed reproducible bacterial strain behavior, which is now questioned.

Purpose of the Study:

• To investigate the variability of Campylobacter colonization in chickens at the population level.
• To determine if isogenic wild-type strains exhibit predictable competitive colonization.
• To identify factors contributing to colonization variability in a chicken model.

Main Methods:

• Construction of individually identifiable wild-type isogenic tagged strains (WITS) with indistinguishable phenotypes.
• Infection of 2-week-old chickens with mixtures of WITS, both simultaneously and through cohousing.
• Monitoring of relative subpopulation amounts to assess colonization dynamics.
• Analysis of potential contributing factors like founder effects and transmission.

Main Results:

• Unpredictable variations in Campylobacter population structure were observed within and between experiments.
• Variability occurred in both simultaneous infections and cohousing experiments.
• Evidence suggests founder effects during initial colonization and subsequent bird-to-bird transmission play a role.
• Phenotypic variation may also contribute to the observed inconsistencies.

Conclusions:

• Campylobacter colonization in chickens is highly variable and not easily predictable, even with isogenic strains.
• Founder effects and transmission dynamics significantly influence colonization patterns.
• Simple colonization models neglecting these factors are inadequate for Campylobacter.
• Results impact the design and interpretation of competition experiments for Campylobacter control.