Nasal Carriage of Antimicrobial-Resistant Staphylococci by Fallow Deer (Dama dama) Taken in a Natural Park of Tuscany, Central Italy

Wild animals are recognized as significant reservoirs for various zoonotic pathogens, including antibiotic-resistant bacteria. This study aimed to investigate the presence of <i>Staphylococcus</i> spp. strains in fallow deer (<i>Dama dama</i>) inhabiting a natural preserve in Central Italy and to examine the phenotypic and genotypic antimicrobial resistance and the presence of some virulence genes among the isolates. During July and December 2022, nasal swabs were collected from 175 fallow deer, which were then analyzed through bacteriological cultures. In total, 176 <i>Staphylococcus</i> spp. strains were isolated and subsequently identified using MALDI-TOF mass spectrometry. <i>S. aureus</i> was the most abundant species with 66 (37.5%) strains, followed by <i>S. hyicus</i>, 34 (19.31%) strains, <i>S. sciuri</i>, 32 (18.18%) strains, <i>S. chromogenes</i>, 27 (15.34%) strains, <i>S. xylosus</i>, 11 (6.25%) strains, <i>S. warneri</i>, 5 (2.84%) strains, and <i>S. devriesei</i>, 1 (0.56%) strain. Antimicrobial susceptibility was assessed for each isolate via the agar disk diffusion method, testing a panel of 13 molecules belonging to 9 antimicrobial classes. The highest resistance rates were detected for penicillin (29.55%), rifampicin (22.73%), and amikacin (20.45%). Notably, intermediate susceptibility was observed for erythromycin (61.93%), enrofloxacin (28.41%), and ceftiofur (21.02%). Conversely, the strains exhibited particularly high susceptibility to amoxicillin/clavulanic acid (99.43%), cefoxitin (97.73%), and vancomycin (96.02%). Based on the results, 32 (18.18%) isolates were classified as multidrug-resistant (MDR). Two strains of <i>S. chromogenes</i> and one strain of <i>S. xylosus</i>, both resistant to penicillin, tested positive for the <i>blaZ</i> gene. No methicillin-resistant strains were found, and none of the isolates harbored genes associated with enterotoxin and toxic shock syndrome toxin production. This study highlights the potential role of wildlife, particularly fallow deer, as reservoirs of antibiotic-resistant <i>Staphylococcus</i> spp. strains. Such findings underscore the importance of monitoring wildlife for antimicrobial resistance, which could have implications for public health and veterinary medicine.