Distribution of erythromycin resistant genes by induced-resistance. M, 1000DL marker; 1, Blank; 2, S. pneumoniae; 3-4 and 6-8, S. agalactiae, ermB gene; 5, S. agalactiae, mefA gene; 9, S. dysgalactiae, ermB gene; 10, S. uberis, ermB gene.