Representative 2-DE gels and SERPA on supernatant fractions of S. aureus O11 (A) and S. aureus O46 (B). Supernatant samples were prepared from stationary phase cultures of S. aureus strains grown anaerobically on iron-depleted RPMI. Preparative 2-DE gels were Coomassie blue stained (left panel). Gels run in parallel were immunoblotted using the pools of sera obtained from group 1 (infected with O11) animals (middle panels) or from group 2 (infected with O46) animals (right panels). Samples were run in parallel on 13 cm gels (pI 3-10; 14% SDS-PAGE). Spots identified by MS/MS are labeled.