Comparative genomic analysis of Staphylococcus spp. and Mammaliicoccus sciuri suggests potential sharing between dogs...

Staphylococci are a diverse group of bacteria commonly found on the skin and mucosal surfaces of humans and animals. Members of the genus can transition from commensalism to opportunistic pathogenicity. The extent to which close contact facilitates transmission of staphylococci remains misunderstood, particularly at the genomic level. In this context, the present study aimed to investigate the possible transmission of Staphylococcus spp. and Mammaliicoccus sciuri between dogs and their owners.

For this, we used a comparative genomics framework to investigate genomic relatedness, antimicrobial resistance, and virulence gene profiles. A total of 27 bacterial isolates were analyzed by whole-genome sequencing, obtained from thirteen dog-owner pairs selected from a previous study involving 50 dogs and 34 owners, in which the same Staphylococcus spp. was identified in both hosts. The isolates were initially identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF), followed by analyses of resistance and virulence genes, molecular typing, and genomic similarity.

The resistome analysis revealed the presence of clinically relevant antimicrobial resistance determinants. Virulence profiling identified genes associated with host colonization and persistence. Average Nucleotide Identity (ANI) revealed high levels of similarity in several dog- owner pairs (n = 9 pairs, 64.3%), with values exceeding 99.7% and broad genomic coverage, indicating a high degree of genomic relatedness and potential strain sharing. Genomic distance analyses and core-genome phylogeny corroborated these findings, revealing both highly related pairs and genetically distinct lineages. Notably, some pairs exhibited highly similar genomes across multiple analytical approaches, consistent with close genomic relatedness and possible epidemiological linkage, whereas others demonstrated substantial genetic divergence despite close contact. Taken together, the results suggest that bacterial sharing between dogs and their owners may occur in a heterogeneous manner, involving both potential strain sharing and the independent circulation of different lineages. This dual pattern highlights the complexity of microbial exchange within household environments and underscores the role of companion animals as potential reservoirs of antimicrobial-resistant bacteria. These findings reinforce the importance of One Health-based approaches for understanding the circulation and genomic relatedness of staphylococci at the human-animal interface and provide genomic evidence to support surveillance efforts involving companion animals and their owners.