The ermA gene similarly encodes a 23S rRNA methyltransferase mediating the MLS_B resistance phenotype in streptococci and staphylococci. Like ermB, ermA confers cross-resistance to macrolides and inducible clindamycin resistance. Its detection in a clinical isolate indicates that macrolides (and clindamycin) are likely ineffective; alternate should be used (Roberts et al. 1999, Roberts 2008, Hotomi et al. 2009).
Roberts, M. C., Sutcliffe, J., Courvalin, P., Jensen, L. B., Rood, J., & Seppala, H. (1999). Nomenclature for macrolide and macrolide-lincosamide-streptogramin B resistance determinants. Antimicrobial agents and chemotherapy, 43(12), 2823–2830. https://doi.org/10.1128/AAC.43.12.2823
Roberts M. C. (2008). Update on macrolide-lincosamide-streptogramin, ketolide, and oxazolidinone resistance genes. FEMS microbiology letters, 282(2), 147–159.
Hotomi, M., Billal, D. S., Shimada, J., Suzumoto, M., Yamauchi, K., Fujihara, K., & Yamanaka, N. (2005). Increase of macrolide-resistant Streptococcus pneumoniae-expressing mefE or ermB gene in the nasopharynx among children with otitis media. The Laryngoscope, 115(2), 317–320.
