Underrated Staphylococcus species and their role in antimicrobial resistance spreading.

The increasing threat of antimicrobial resistance has shed light on the interconnection between humans, animals, the environment, and their roles in the exchange and spreading of resistance genes. In this review, we present evidences that show that Staphylococcus species, usually referred to as harmless or opportunistic pathogens, represent a threat to human and animal health for acting as reservoirs of antimicrobial resistance genes. The capacity of genetic exchange between isolates of different sources and species of the Staphylococcus genus is discussed with emphasis on mobile genetic elements, the contribution of biofilm formation, and evidences obtained either experimentally or through genome analyses. We also discuss the involvement of CRISPR-Cas systems in the limitation of horizontal gene transfer and its suitability as a molecular clock to describe the history of genetic exchange between staphylococci.