Evaluation of spa typing for the classification of clinical methicillin-resistant Staphylococcus aureus isolates

We evaluated the utility of typing the spa gene, which encodes protein A of Staphylococcus aureus, for analyzing methicillin-resistant S. aureus (MRSA) isolates from patients with health care-associated infections by comparing the results of spa typing with those of pulsed-field gel electrophoresis (PFGE) and multiple-locus variable-number tandem repeat analysis (MLVA). We analyzed 78 clinical MRSA isolates collected at our hospital over a period of 2 months. The clinical isolates were found to have 12 different spa types, with approximately 82% (64/78) of them being typed as t002. The same clinical MRSA isolates were classified into 15 and 19 types upon MLVA and PFGE analysis, respectively, and 19 and 28 types when spa typing was used in combination with MLVA and PFGE, respectively. The discriminatory ability of spa typing alone is low, and thus indicating that this technique is insufficient for performing the initial genotyping of MRSA in short-term epidemiological studies. Therefore, spa typing should be used in combination with MLVA or PFGE for further typing of MRSA isolates.