MEFE IS NECESSARY FOR THE ERYTHROMYCIN-RESISTANT M-PHENOTYPE IN STREPTOCOCCUS-PNEUMONIAE

Recently, it was shown that a significant number of erythromycin-resis tant Streptococcus pneumoniae and Streptococcus pyogenes strains conta in a determinant that mediates resistance via a putative efflux pump. The gene encoding the erythromycin-resistant determinant was cloned an d sequenced from three strains of S. pneumoniae bearing the M phenotyp e (macrolide resistant but clindamycin and streptogramin B susceptible ). The DNA sequences of mefE were nearly identical, with only 2-nucleo tide differences between genes from any two strains. When the mefE seq uences were compared to the mefA sequence from S. pyogenes, the two ge nes were found to be closely related (90% identity). Strains of S. pne umoniae were constructed to confirm that mefE is necessary to confer e rythromycin resistance and to explore the substrate specificity of the pump; no substrates other than 14- and 15-membered macrolides were id entified.