Predominance of 23S rRNA Mutants among Non-Erm, Non-Mef Macrolide-Resistant Clinical Isolates of Streptococcus pneumoniae Collected in the United States in 1999-2000

A total of 322 erythromycin-resistant pneumococci from TRUST 3 and TRUST 4 United States surveillance studies (1999-2000) were screened for 23S rRNA, L4, and L22 gene mutations. Nineteen isolates, two with mefA, had mutations at position 2058 or 2059 in 23S rRNA. Two had a 69GTG71-to-TPS substitution in L4; one of these also contained ermA.