Phylogenetic relationships among Staphylococcus aureus isolated from clinical samples in Mashhad, Iran

Summary: The spa gene occurs in all strains of Staphylococcus aureus (S. aureus), can function as a genetic marker and might be used distinguish strains at the species level. Hence, due to these advantages, we used spa typing and the Based Upon Repeat Pattern (BURP) to assign the clonal and phylogenetic relationships of S. aureus strains. The sensitivity of S. aureus strains to methicillin was determined using agar disk diffusion. The extracted DNA from 56 isolates of S. aureus was subjected to PCR to detect the spa gene with specific primers. The spa typing method was performed for each of the isolates, and then, BURP was used to cluster spa types (spa-CCs). Finally, using relevant software, the phylogenic tree was drawn. The results of this study showed that 25 out of 56 (44.6%) isolates were resistant to methicillin. The typing of S. aureus isolates revealed 24 different spa types among 56 isolates, and BURP analysis clustered the 24 spa types into 5 spa clonal complexes (CCs) and 12 singletons. The process of spa typing, in combination with BURP analysis, provides an efficient method for investigating phylogenetic and clonal relationships among clinical isolates and can be useful for monitoring bacterial spread between hospitals and communities as well as between and within hospitals. Keywords: Staphylococcus aureus, spa gene, BURP, Phylogenetic relationship