Multiple differences in pathogen-host cell interactions following a bacterial host shift.

Area of Science:

• Microbiology
• Disease Ecology
• Evolutionary Biology

Background:

• Novel disease emergence often involves pathogen trait changes for host adaptation.
• Bacterial pathogens may differ significantly from viruses in life history and host-shift mechanisms.
• Understanding bacterial host shifts is crucial for preventing infectious disease outbreaks.

Purpose of the Study:

• To investigate the cellular interaction capabilities of Mycoplasma gallisepticum strains responsible for epizootic outbreaks in house finches.
• To compare the adherence, invasion, intracellular persistence, and cytotoxicity of house finch-origin strains against poultry strains in model avian cells.

Main Methods:

• In vitro assays using cultured chicken embryonic fibroblasts.
• Comparison of house finch epizootic outbreak strains (e.g., HF_1994) with reference virulent (R_low) and attenuated (R_high) poultry strains.
• Assessment of bacterial adherence, invasion, intracellular survival, and cytotoxicity.

Main Results:

• House finch epizootic outbreak strains demonstrated superior adherence, invasion, intracellular persistence, and exit from chicken embryonic fibroblasts compared to poultry strains.
• The house finch strain HF_1994 exhibited reduced cytotoxicity and even a cytoprotective effect on avian cells.
• Poultry strains showed higher cytotoxicity towards avian cells.

Conclusions:

• Mycoplasma gallisepticum strains causing house finch epizootics appear adapted to intracellular environments, potentially aiding colonization and immune evasion in the novel host.
• This intracellular invasion phenotype may have been critical for the successful host shift from poultry to house finches.
• Further studies are needed to confirm these interactions in house finch cells and their role in host-shift success.