First clinical isolate in Europe of clindamycin-resistant group B Streptococcus mediated by the lnu(B) gene

We characterize the mechanisms implicated in an unusual phenotype of resistance to macrolides-lincosamides (no halos of inhibition around clindamycin and lincomycin discs, and a 15 mm halo around erythromycin disc) in a Streptococcus agalactiae isolate recovered in Spain. The presence of macrolide or lincosamide resistance genes [erm(A), erm(B), erm(C), erm(T), mef(A), mrs(A), lnu(A), lnu(B), lsa(B), lsa(C) and vga(C)] was investigated by PCR and sequencing. The strain showed a resistant phenotype to erythromycin and clindamycin (MIC = 2 mg/L and MIC = 8 mg/L, respectively) and the presence of lnu(B) and mef(A) genes was demonstrated. Clinical microbiology laboratories should be aware of this unusual phenotype due to the association of two mechanisms mediated by lnu(B) and mef(A) genes. This constitute, to our knowledge, the first report of lnu(B) in S. agalactiae in human isolates in Europe.