A Novel Erythromycin Resistance Methylase Gene (ermTR) in Streptococcus pyogenes

Erythromycin resistance among streptococci is commonly due to target site modification by an rRNA-methylating enzyme, which results in coresistance to macrolide, lincosamide, and streptogramin B antibiotics (MLS(B) resistance). Genes belonging to the ermAM (ermB) gene class are the only erythromycin resistance methylase (erm) genes in Streptococcus pyogenes with MLS(B) resistance that have been sequenced so far. We identified a novel erm gene, designated ermTR, from an erythromycin-resistant clinical strain of S. pyogenes (strain A200) with an inducible type of MLS(B) resistance. The nucleotide sequence of ermTR is 82.5% identical to ermA, previously found, for example, in Staphylococcus aureus and coagulase-negative staphylococci. Our finding provides the first sequence of an erm gene other than ermAM that mediates MLS(B) resistance in S. pyogenes.