Bats as Hosts of Antimicrobial-Resistant Mammaliicoccus lentus and Staphylococcus epidermidis with Zoonotic Relevance

Bats are increasingly recognized as reservoirs for antimicrobial-resistant bacteria, playing a potential role in the dissemination of resistance genes across species and regions. In this study, 105 bats from 19 species in Portugal were sampled to investigate the presence, antimicrobial resistance, and genetic characteristics of <i>Mammaliicoccus</i> and <i>Staphylococcus</i> isolates. Thirteen <i>Mammaliicoccus lentus</i> and <i>Staphylococcus epidermidis</i> were recovered. Antimicrobial susceptibility testing revealed multidrug resistance in three isolates, with <i>S. epidermidis</i> carrying <i>mph</i>(C), <i>msr</i>(A), and <i>dfr</i>C genes, and <i>M. lentus</i> harboring <i>sal</i>B, <i>tet</i>(K), and <i>str</i>. Notably, <i>qac</i>A was detected in <i>S. epidermidis</i>, highlighting its plasmid-associated potential for horizontal gene transfer to more pathogenic bacteria. Heavy metal resistance genes (<i>ars</i>B and <i>cad</i>D) were also identified, suggesting the role of environmental factors in co-selecting antimicrobial resistance. Molecular typing revealed the <i>S. epidermidis</i> strain as ST297, a clone associated with both healthy humans and invasive infections. These findings emphasize the need for monitoring bats as reservoirs of resistance determinants, particularly in the context of zoonotic and environmental health. The presence of mobile genetic elements and plasmids further underscores the potential for the dissemination of resistance. This study reinforces the importance of adopting a One Health approach to mitigate the risks associated with antimicrobial resistance.