Association of virulence genes of Staphylococcus aureus and somatic cell count in clinical and subclinical mastitis cases in Alborz province during April to September 2014

The aim of present study was to detect some important virulence genes of Staphylococcus aureus that were isolated from clinical and subclinical mastitis cases and their correlation with Somatic Cell Count (SCC) as inflammatory indicator of udder was found. Presence of six important genes “clfA, coa, SpaA, agrIII, hla and hlb” encoding clamping factor, coagulase, X region of protein A gene spa, accessory gene regulator, hemolysin A and hemolysin B, respectively, were detected using PCR and the results were compared with SCC. After statistical analysis, a significant correlation between virulence genes and increase in somatic cells was observed (P ≤ 0/05). According to the results, the six virulence gene patterns except one, were presented only in the clinical mastitis isolates and all these isolates were corelated to SCC above 5000000 cell/ml. According to the results, increase in virulence genes that were present in Staphylococcus aureus could lead to change the signes of intra mammary infection from subclinical to clinical mastitis. Furthermore, the results indicates that increasing in the number of virulence genes present in Staphylococcus aureus improves virulence of bacteria to damage mammary tissues, which leads to increase in SCC.