A variety of Gram-positive bacteria carry mobile mef genes

The mefE gene codes for a membrane bound efflux protein, which confers resi stance to macrolides, and has been identified in Streptococcus pneumoniae. A variety of Gram-positive organisms were examined. Twenty-six isolates of S. pneumoniae carried mefE and were resistant to erythromycin (MIC of 2-16 mg/L). Two additional isolates of Em(r) S. pneumoniae carried both ermB and mefE(MIC of 16-128 mg/L). One Micrococcus luteus, one Corynebacterium jeik eium, three Corynebacterium spp., two viridans streptococci and seven Enter ococcus spp. also carried mef genes. It was possible to move the mef gene f rom all 11 S. pneomoniae tested to susceptible S. pneumoniae and/or Enteroc occus faecalis recipients. The addition of DNase (1 g/L) did not affect the gene transfer. It was also possible to move the mef gene from donor Entero coccus spp., viridans streptococci, M. luteus, C. jeikeium and Corynebacter ium spp. to E. faecalis recipients. Transconjugant isolates were resistant to erythromycin (MIC = 16 mg/L). Hybridization with a labelled mef oligonuc leotide probe against Southern blots and bacterial dot blots confirmed the presence of the mef genes. This is the first time that a mobile mef gene ha s been identified in four different genera, from three distinct geographica l locations.