CONICET | Buscador de Institutos y Recursos Humanos

Background: Recently, we reported the first detection of the lnuB gene in Streptococcus agalactiae outside Canada. During 2008, two unrelated isolates of S. agalactiae resistant to clindamycin but susceptible to erythromycin were recovered in the same hospital. As this lincosamide nucleotidyl transferase is still rare in this microorganism, we tried to uncover the genetic basis of this unusual phenotype dissemination. Methods: Three unrelated S. agalactiae isolates were obtained from vagina and rectum swabs (two isolates) of pregnant females, while one from a glans lesion of a male. Detection of GBS colonization was performed according to universal screening recommendations. Identification was confirmed by conventional schemes. Antimicrobial susceptibility (disk diffusion) was evaluated following CLSI recommendations. Isolates were screened by PCR for ermB, mef and lnuB determinants. A thermal asymmetric interlaced (Tail)-PCR was used to study the lnuB flanking regions and the resulting fragments were sequenced. Results: All the isolates were penicillin and erythromycin susceptible but resistant to clindamycin and lincomycin. No PCR products were obtained for the common resistance determinants in the analyzed isolates. However, lnuB was detected by PCR. The sequencing of lnuB and his neighboring region in the three unrelated isolates showed identity to plasmid pEF418 from Enterococcus faecium. Conclusion: Even if only more sequencing will provide definitive results, the identity of lnuB flanking regions detected in S. agalactiae to those of pEF418 (a putative ABC transporter ATP-binding protein and a non coding region, upstream and downstream respectively) suggest the origin to E. faecium plasmids disseminating into other genus, or a similar origin for both species, if recruitment was from a common source.

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