Genetic environment of lnuB gene in Streptococcus agalactiae

MONTILLA PIEDRAHITA A; ZAVALA A; CACERES R; CITTADINI R; VAY C; GUTKIND G; FAMIGLIETTI A; BONOFIGLIO L; MOLLERACH M

Denver

Conferencia; 53rd Interscience Conference on Antimicrobial Agents and Chemotherapy; 2013

American Society for Microbiology

Background: Resistance to lincosamides in S. agalactiae is commonly mediated by Erm-type methylases, which confer cross-resistance to macrolide, lincosamide and streptogramins B. Previously, we reported the first detection of the lnuB gene in Streptococcus agalactiae (GBS) outside Canada. During 2007-2012, 8 epidemiological unrelated isolates of S. agalactiae resistant to clindamycin but susceptible to erythromycin were recovered in two different hospitals. The aim of this study was to determine the genetic environment of lnuB gene detected in S. agalactiae strains as well as to gain knowledge on the dissemination elements of this uncommon resistance gene. Methods: Eight unrelated S. agalactiae isolates were obtained from different sources. MICs were evaluated following CLSI recommendations. All isolates were screened by PCR for ermB, mef and lnuB determinants. ApaI- PFGE was performed for clonal assessment. PCR-mapping, TAIL-PCR strategies and sequencing were used for studying lnuB environment. Results: The eight isolates showing L phenotype were susceptible to erythromycin, MIC =0.01-0.06 mg/L, but resistant R positive only for lnuB gene, and confirmed by DNA sequencing. PFGE analysis revealed a single clone associated with this phenotype The genetic environment of lnuB was analyzed by sequencing in one strain (SGB76) The 10,385 kb lnuB-carrying segment show high nucleotide identity to the corresponding region of plasmid pV7037 from Staphylococcus aureus SA7037 (99%; 9698/9717 bp). The novel element is flanked by a copy of IS1216 and ISL3 transposase (tnp) gene. Conclusions : To our knowledge, this is the first report of a lnuB platform architecture in S. agalactiae. The presence of two insertion sequences flanking the structure indicates that dissemination of the lnuB gene could occur by lateral transfer, possibly mediated by this element.