Analysis of resistant subpopulations of Thai MRSA strains to vancomycin (A) and teicoplanin (B). Three Thai strains, MR135, MR187, and MR209, contained subpopulations resistant to 4 to 6 μg of vancomycin per ml (A) and 8 μg of teicoplanin per ml (B), in contrast to Thai strain MR126 and S. aureus type strain FDA209P. When compared to Japanese strain Mu3, Thai strains did not contain subpopulations resistant to 7 to 9 μg of vancomycin per ml but MR135 had larger sizes of subpopulations resistant to 2 to 5 μg of vancomycin per ml. Mu50 is a Japanese MRSA strain for which the vancomycin MIC is 8 μg/ml.