Characterization of 58 S. pyogenes test strains carrying erm(B) as the sole erythromycin resistance gene, subdivided according the P/G combinations displayed

P/G combination designation (no. of strains)MLS resistance phenotypeSusceptibility to tetracycline (MIC range)aPCR evidence of gene:Distance (kb) between linked erm(B) and tet(M)erm(B) location
A (14)iMLS-AS (0.125-0.25)++1.090Tn1116
B (21)cMLSR (32-128)+++9.9Tn6002
C (8)cMLSR (32-64)++++1.102Tn3872-like
D (4)cMLSS (0.125-0.25)++++1.102Tn3872-like
E (3)cMLSS (0.125-0.25)++1.090Tn1116-like
F (6)cMLSS (0.125-0.25)Chromosome
G (2)cMLSS (0.125-0.25)++Tn917b
  • a S, susceptible; R, resistant. MICs are expressed in μg/ml.

  • b Likely carried by a plasmid.