We performed molecular characterization (MLST, spa typing, and PVL testing) on all 366 isolates. MLST was performed as previously described.7 (link) Briefly, internal fragments of seven housekeeping genes were amplified by PCR and sequenced using the ABI Big Dye Terminator Cycle Sequencing Kit v3.1 (Applied Biosystems, Foster City, CA). MLST STs were assigned using the online S. aureus MLST database (www.mlst.net ). MLST STs were clustered into MLST CCs using eBURST, with the minimum number of common alleles set at six of seven.6 (link)spa typing was performed on isolates by amplifying and sequencing the spa repeat region using primers as previously described.13 (link)spa sequence analysis was performed using Ridom StaphType (VERSION 2.0; Ridom GmbH, Würzburg, Germany), and the resulting spa types were then clustered into related spa CCs using the BURP algorithm with parameters set to exclude spa types that are shorter than five repeats and if costs were less than or equal to four.
We tested for the presence of the PVL genes using PCR amplification and gel electrophoresis using primers and PCR conditions as described previously.7 (link)
We tested for the presence of the PVL genes using PCR amplification and gel electrophoresis using primers and PCR conditions as described previously.7 (link)
