Staphylococcus aureus are commensal bacteria present on skin and mucosae in both humans and animals, but they can also be found in food, water and in various environments. They are also considered a major pathogen having a great morbidity leading to a wide range of infections. They are included in the list of most virulent and antimicrobic resistant bacterial pathogens (ESKAPE, Escherichia coli, Staphylococcus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterococcus faecalis and faecium)) by the Center for Disease Control and Prevention (CDC), and S. aureus is part of the worldwide threat represented by the presence of antimicrobial resistance (AMR). The outcomes of an epidemiological investigation on 26,430 S. aureus isolates from a global public database (NPDIB; NCBI Pathogen Detection Isolate Browser) support the evidence of significant differences in the distribution of isolates and ARGs (Antimicrobial Resistance Genes) clusters among geographical areas of origin and among sources of the isolates. Moreover, the ARGs cluster patterns suggest an association between the isolates from human and animal populations. This outcome and the large diffusion of the pathogens among human and animal populations support the importance of gaining information on the epidemiology of these infections with a One Health approach.

Staphylococcus pseudintermedius (SP) is an emergent zoonotic agent associated with multidrug resistance (MDR). This work aimed to describe the antibacterial activity of four essential oils (EOs) and silver nanoparticles (AgNPs) against SP. Fifteen SP strains were tested. The four EOs, namely Rosmarinus officinalis (RO), Juniperus communis (GI), Citrus sinensis (AR) and Abies alba (AB), and AgNPs were used alone and in combination to determine the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) against SP. All strains presented MDR and methicillin resistance. Among the antibiotic cohort, only rifampicin, doxycycline and amikacin were effective. When EOs were tested alone, AB showed the lowest MIC followed by GI, RO and AR (0.23%±0.3; 0.5%±0.51; 0.79%±0.39; 0.93%±0.63). MBC was increased with the following order: AB, GI, AR and RO (3.56%±4.87; 4.93%±6.27; 8.53%±7.2; 10.34%±5.31). MIC and MBC values for AgNPs were 10.74 mg/L±4.23; 261.05 mg/L±172.74. In combination, the MIC and MBC values were lower for all compounds. In conclusion, EOs and AgNPs could be considered as promising antibacterial alternatives to antibiotics.