Poultry farms are hotspots for the development and spread of antibiotic resistance genes (ARGs), due to high stocking densities and extensive use of antibiotics, posing a threat of spread and contagion to workers and the external environment. Here, we applied shotgun metagenome sequencing to characterize the gut microbiome and resistome of poultry, workers and their households - also including microbiomes from the internal and external farm environment - in three different farms in Italy during a complete rearing cycle. Our results highlighted a relevant overlap among the microbiomes of poultry, workers, and their families (gut and skin), with clinically relevant ARGs and associated mobile elements shared in both poultry and human samples. On a finer scale, the reconstruction of species-level genome bins (SGBs) allowed us to delineate the dynamics of microorganism and ARGs dispersion from farm systems. We found the associations with worker microbiomes representing the main route of ARGs dispersion from poultry to human populations. Collectively, our findings clearly demonstrate the urgent need to implement more effective procedures to counteract ARGs dispersion from poultry food systems and the relevance of metagenomics-based metacommunity approaches to monitor the ARGs dispersion process for the safety of the working environment on farms.

The aim of this study was to assess how raising chickens without the use of antimicrobials affects the microbiome of poultry carcasses. A total of 151 caeca and neck skin samples from chickens raised without antimicrobials were collected in the same slaughterhouse and submitted to shotgun metagenomic sequencing. Caeca were dominated by Bacillota and Bacteroidota, while carcasses by Pseudomonadota. The caeca microbiome was enriched in genes related to a proliferating and metabolically active microbial community. Carcass-associated microbiomes were enriched in functional genes linked to adaptation to nutritionally limited and oxidative environments. A significantly higher cumulative antimicrobial resistance gene abundance was detected in carcasses compared to caeca. Specifically, carcasses exhibited approximately 1.5 times more AMR genes, reflecting an increase of nearly 49%. While caeca showed enrichment of resistance determinants associated with Gram-positive anaerobic gut commensals, carcasses were characterized by a predominance of multidrug efflux systems and clinically relevant β-lactam resistance genes, commonly associated with environmental and opportunistic Gram-negative bacteria. In carcasses, carbapenem-associated genes, such as OXA-58-like and CphA, were detected. However, these genes have not been associated with carbapenemase-producing Enterobacterales. Overall, the findings of this study indicate that reducing antimicrobial resistance in food animal production systems extends beyond farm-level intervention. At present, the benefits of the interventions aimed at reducing antimicrobial resistance at farm level seem to be compromised during the post-harvest stages.