Agarose gel immunodiffusion analysis of bacterial extracts (1 to 12) with the following absorbed sera: anti-type 8 serum, unconcentrated (A); anti-serotype 18 serum, concentrated threefold (B to D); and anti-S. epidermidis 2213 serum, concentrated threefold (E). S. aureus extracts were as follows: 1, type 8; 2, serotype 18; 3, MRSA1; 4, MRSA2; and 5, MRSA3. S. epidermidis extracts were as follows: 6, 2034; 7, 2038; 8, 2213; 9, 2216; 10, 2222; 11, 2227; and 12, 2214. All extracts were diluted 1:2 in PBS.