Molecular fingerprinting of Staphylococcus aureus isolated from patients with osteomyelitis in Argentina and clonal distribution of the cap5(8) genes and of other selected virulence genes

The molecular fingerprinting of a collection of 94 Staphylococcus aureus isolates from patients with osteomyelitis in Argentina was performed. Twenty-three SmaI pulsed-field gel electrophoresis (PFGE) types and 37 spa types were identified. The isolates were assigned to 23 sequence types (STs). The proportion of methicillin-resistant S. aureus (MRSA) isolates was significantly higher among cap5 S. aureus (35/61) compared with cap8 S. aureus (8/33) isolates (p = 0.0025). Twenty-four of the 94 isolates carried the lukS-PV/lukF-PV genes, which were significantly associated to cap5 [(23/38) compared with cap8 S. aureus isolates (1/32) (p = 0.0001)]. Forty of the 94 isolates carried genes of the egc locus (seg/sei). The distribution of seg/sei genes among isolates was related to certain clones. Isolates of the four agr types were found in the S. aureus collection. Whereas agr I isolates were evenly distributed among cap5 and cap8 S. aureus isolates (32/61 and 14/33, respectively), the agr II group was composed of 29 cap5 S. aureus isolates and agr III was composed of 16 cap8 S. aureus isolates. Two clones originally associated to animals (ST 188, 7 isolates and ST 1796, 5 isolates) were associated with chronic osteomyelitis and lack of capsular polysaccharide (CP) production. Loss of CP production remains the single factor among those investigated that is associated with chronic osteomyelitis.