Staphylococcus aureus is the leading etiologic agent of orthopedic implant infections. Here a ribocluster of 27 S. aureus strains underwent further molecular characterization and subtyping by multilocus sequence typing (MLST) and spa-typing. This cluster had been detected by automated ribotyping (with the EcoRI restriction enzyme) of 200 S. aureus isolates from periprosthetic infections of patients who underwent revision at the Rizzoli Orthopaedic Institute. The ribocluster, consisting of agr type III strains, with a 74% co-occurrence of bone sialoprotein-binding (bbp) and collagen-binding (cna) genes, lacked mecA and IS256, and exhibited a high prevalence of the toxic shock syndrome toxin gene (tst, 85%). Strains' relatedness was analyzed by BURP and eBURST. Two predominant spa types, t012 (32%) and t021 (36%), and one predominant sequence type, ST30 (18/27, 67%) were identified: a S. aureus lineage spread worldwide belonging to MLST CC30. Two new sequence types (ST2954, ST2960) and one new spa type (t13129) were detected for the first time. Interestingly, the 27-strain cluster detected by ribotyping corresponded exactly to MLST CC30, the sole CC identified by eBURST.
Keywords: methicillin-sensitive Staphylococcus aureus; multilocus sequence typing; orthopedic implant infections; spa-typing; virulence factors.