NOVEL MECHANISM OF MACROLIDE RESISTANCE IN STREPTOCOCCUS-PNEUMONIAE

The mechanism of macrolide resistance was examined in 73 clinical isol ates of Streptococcus pneumoniae. Two distinct resistance phenotypes w ere observed: high-level macrolides-lincosamides-streptogramin B (MLS) resistance and low-level macrolide resistance with lincosamide suscep tibility. High-level MLS resistance was associated with the presence o f ermAM. Strains with the low-level resistant phenotype (novel) were n egative for ermA, ermC, ermAM, ereA, ereB and msrA by polymerase chain reaction (PCR) amplification with gene-specific primers. Ribosomes is olated from novel strains bound the same amount of [C-14]-erythromycin as ribosomes from sensitive strains. These novel strains also did not inactivate the macrolide. The novel mechanism was found in 41% of the erythromycin resistant S. pneumoniae examined. (C) 1996 Elsevier Scie nce Inc.