Development of macrolide resistance by ribosomal protein L4 mutation in Streptococcus pyogenes during miocamycin treatment of an eight-year-old Greek child with tonsillopharyngitis.

Streptococcus pyogenes isolates with the same pulsed-field patterns were recovered from the throat cultures of a child with tonsillopharyngitis before and after treatment with miocamycin, a 16-membered macrolide. The initial isolate was macrolide-susceptible, but the isolates after the treatment were resistant to 14 and 15-membered macrolides and had two amino acid (65WR66) deletions in ribosomal protein L4.