Anthropogenic Pressure Drives Antimicrobial Resistance in Wildlife: A Metagenomic Analysis

Human activity appears to fundamentally alter the gut genetics of the Eurasian wild boar. While the interface between livestock and humans is well-trodden ground, the specific dynamics of antimicrobial resistance in wildlife—particularly in Southwest Asia—have remained poorly characterised. This study addresses that blind spot, integrating genetic data with tissue pathology to map how anthropogenic pressure infiltrates the wild microbiome.

Profiling Antimicrobial Resistance in Wildlife

To understand the significance of these findings, one must look at the depth of the analysis. Rather than relying on simple detection methods that might miss the broader context, the researchers employed shotgun metagenomic sequencing. This approach allowed for the comprehensive characterisation of the resistome composition, identifying not just the presence of resistance but the specific pathogenic lineages and mobile genetic elements involved. By capturing the full genetic potential within the samples, the study could pinpoint broad-host-range plasmids carrying resistance, providing a granular view of the bacterial ecosystem that narrower screening methods often obscure.

Correlating Inflammation with Resistance

The researchers collected samples from 87 wild boars across a defined anthropogenic gradient in Iran, ranging from protected forests to peri-urban agricultural landscapes. The data is compelling. Boars living under high anthropogenic pressure did not merely carry more resistance genes; they exhibited physical signs of illness. Quantitative histopathology revealed chronic enteritis, characterised by villus atrophy and immune cell infiltration, in the animals carrying the highest resistance loads. This suggests that the boars are not passive carriers but are experiencing active dysbiosis or subclinical infection.

The specific pathogens identified are concerning. High-pressure zones yielded Escherichia coli sequence type ST131, a pandemic clone frequently associated with human clinical infections. These bacteria carried extended-spectrum β-lactamase (ESBL) genes on broad-host-range plasmids. The implication is that these animals are acquiring resistance mechanisms directly from the human-livestock interface.

Implications and Limitations

While the study effectively measures the burden of resistance genes, the directionality of transmission remains a hypothesis derived from the statistical association. The data confirms that anthropogenic pressure is the dominant predictor of ARG abundance. It suggests that wild boars function as reservoirs, potentially amplifying these pathogens. Crucially, the link between tissue inflammation and resistance load provides mechanistic evidence that these gut ecosystems are under stress, facilitating the persistence of resistance at the landscape scale.