S. lutetiensis susceptible to erythromycin but resistant to clindamycin; analysis of the genetic basis.

ARIAS B; KOVACEC V; ALMUZARA M; CITTADINI R; VERA OCAMPO C; MONTILLA PIEDRAHITA A; RAMIREZ MS; VAY C; BONOFIGLIO L; MOLLERACH M

Simposio; XIX Lancefield International Symposium on Streptococci & Streptococcal Diseases; 2014

Lancefield Society

Lincosamide nucleotidyltransferase enzymes encoded by members of the lnu gene family are one of the mechanisms involved in resistance to lincosamides. Among streptococci, lnu(B) gene was also described in Streptococcus agalactiae; Streptococcus dysgalactiae ssp. equisimilis and in Streptococcus uberis. Previously we report a case of bacteremia caused by Streptococcus lutetiensis resistant to clindamycin but susceptible to erythromycin. It was the first report of the presence of lnu(B) gene encoding the lincosamide nucleotidyl-transferase enzyme as responsible of clindamycin resistance. lnu(B) sequence was deposited in the EMBL/GenBank/DDBJ databases under accession number KC688833. MICs for S. lutetiensis strain 175 (SL175) were as follows (μg/mL): penicillin 0.032; ceftriaxone 0.023; vancomycin 0.38; ciprofloxacin 0.75; erythromycin 0.064; clindamycin 2.0 and lincomycin 128.The phenotypic characterization was complemented by a modified triple disk induction test in which lincomycin and clindamycin disks were placed at the sides of an erythromycin disk 15 mm apart. No inhibition zones was observed around clindamycin and lincomycin disks and no inducible pattern was detected. The isolate was also tested for ermB, ermTR and mefA/E with negative results. Recently it was described the LSAP phenotype which includes resistance to lincosamides, streptogramins A and pleuromutilins, in S. agalactiae and Staphylococcus aureus In this work we explore the resistance to pleuromutilins and the genetic environment of the lnuB gene in SL175 in order to contribute to the understanding of the genetic dissemination of this resistance marker. Methods: Tiamulin MIC was performed by broth dilution method according to CLSI recommendations for Streptococcus spp. viridans group. The genetic environment of lnu(B) was mapped in SL175 strain using a PCR- scheme covering the 12,076 kb fragment previously characterized in Streptococcus agalactiae. Flanking regions and the resulting fragments were sequenced. Results: Tiamulin MIC was 8μg/ml. Considering this MIC value for tiamulin and previous results of lincomycin and clindamycin resistance in SL175, the LP phenotype could be defined for this isolate. The genetic environment of the lnu(B) gene is similar to the platform previously described by us in S. agalactiae. The lsa gene was confirmed by PCR mapping and sequencing. Conclusions: The lsa gene located immediately upstream of the lnu(B) gene encodes an ABC transporter involved in active efflux of lincosamides, streptogramins A and pleuromutilins, so the contribution of this marker to clindamycin resistance could not be disregarded. The identity of lnu(B) flanking regions detected in S. lutetiensis to those of S. agalactiae suggest that the same platform could be involved in is the dissemination of these resistance markers in the Streptococcus genus.