FnBPA A domain typing of S. aureus strains by dot blot hybridization. Genomic DNA from S. aureus isolates was purified, and the fnbA gene fragment encoding the entire A domain was amplified by PCR. Five ng purified fnbA DNA from each isolate was spotted onto nitrocellulose membranes and probed with DIG-labelled fnbA type-specific probes corresponding to isotype I (a), isotype II (b), isotype III (c), isotype IV (d) and isotype V (e). fnbA DNA from isolates 8325-4, MRSA252, MSSA476, P1 and 3110 (top row of blots) were used as controls. The MLST genotypes of strains typed here are given in Table 1.