Virulence and antimicrobial resistance genes detected in Staphylococcus spp. isolated from clinical and non-clinical mastitis using whole-genome sequencing

Staphylococcus spp. are among the most isolated bacteria in clinical and subclinical mastitis cases in dairy cattle. The genus comprises biofilm-forming bacteria capable of producing toxins and acquiring resistance to multiple drugs. This work aimed to evaluate the genetic profile related to virulence and antimicrobial resistance characteristics of Staphylococcus spp., isolated from clinical mastitis and non-clinical fresh cows using whole genome sequencing (WGS). The bacterial collection consisted of 29 Staphylococcus strains isolated from clinical cases of mastitis (n = 7), as well as milk samples collected from fresh cows (n = 22). Strains were identified as Staphylococcus aureus (n = 2), Staphylococcus chromogenes (n = 19), and Staphylococcus haemolyticus (n = 8). A total of 94 virulence genes were observed, including pvl, icaA, icaD genes, and microbial surface components that recognize adhesive matrix molecules (MSCRAMMs). We also detected important resistance genes such as blaZ, ant(4), erm(B), fexA, lnu(D), tet(L), and tet(M). The phylogenetic tree listed the species as expected and presented four clades. A variety of virulence and resistance genes were detected. In addition, the expression of important genes such as those responsible for the formation of biofilms and enterotoxins may represent a risk to the health of consumers. being a concern for public health.