Discrimination of Staphylococcus aureus isolates on the basis of gene coding protein A using PCR-restriction enzyme analysis

In a comparative study, isolates of Staphylococcus aureus from bovine mastitis cases with known coa and aroA types were analyzed by molecular typing based on polymerase chain reaction and restriction enzyme analysis (REA) of protein A-encoding gene (spa) for assessment of its utility over coa and aroA typing in discrimination of the isolates. Fifty-eight isolates of S. aureus from nine dairy herds in two Iranian provinces were typed based on polymorphism characterizing the gene encoding for the X region of protein A (spa). Five differently sized amplicons of approximately 1,200 bp to 1,410 bp were observed. Spa gene REAs produced a total of eight distinct patterns, designated as S1–S8, after digestion with restriction endonuclease Hin6I. For the spa gene, the lack of amplification was also considered a distinct genotype (S9). The majority of isolates were classified into spa types S2 (24.14%) and S6 (24.14%). This study also showed that genetic analysis of the repeat region of protein A might help to understand the distribution of prevalent S. aureus clones among bovine mastitis isolates. Interestingly, based on spa, coa, and aroA typing, some isolates which were identified as dominant types by one method were classified as rare types by another and vice versa. Finally, spa typing has 62.1% concordance with coa typing from the standpoint of the assignment of the isolates to predominant and rare lineages. This study also demonstrates the importance of spa genotyping in the discrimination of S. aureus isolates, which were otherwise indistinguishable by coa and aroA gene typing.