Staphylococcus aureus Isolates from Bovine Mastitis in Eight Countries: Genotypes, Detection of Genes Encoding Different Toxins and Other Virulence Genes

<i>Staphylococcus aureus</i> is recognized worldwide as one of the major agents of dairy cow intra-mammary infections. This microorganism can express a wide spectrum of pathogenic factors used to attach, colonize, invade and infect the host. The present study evaluated 120 isolates from eight different countries that were genotyped by RS-PCR and investigated for 26 different virulence factors to increase the knowledge on the circulating genetic lineages among the cow population with mastitis. New genotypes were observed for South African strains while for all the other countries new variants of existing genotypes were detected. For each country, a specific genotypic pattern was found. Among the virulence factors, <i>fmtB</i>, <i>cna</i>, <i>clfA</i> and leucocidins genes were the most frequent. The <i>sea</i> and <i>sei</i> genes were present in seven out of eight countries; <i>seh</i> showed high frequency in South American countries (Brazil, Colombia, Argentina), while <i>sel</i> was harboured especially in one Mediterranean country (Tunisia). The <i>etb</i>, <i>seb</i> and <i>see</i> genes were not detected in any of the isolates, while only two isolates were MRSA (Germany and Italy) confirming the low diffusion of methicillin resistance microorganism among bovine mastitis isolates. This work demonstrated the wide variety of <i>S. aureus</i> genotypes found in dairy cattle worldwide. This condition suggests that considering the region of interest might help to formulate strategies for reducing the infection spreading.