Molecular analysis of lincomycin resistance and clonal relatedness of clinical Streptococcus alagaltiae isolates

ARIAS B; MONTILLA PIEDRAHITA A; KOVACEC V; CACERES R; CITTADINI R; GARCÍA S; VAY C; GUTKIND G; FAMIGLIETTI A; BONOFIGLIO L; MOLLERACH M

Buenos Aires

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. Previously we reported the detection of the lnu(B) gene in a Streptococcus Group B (SGB) strain (SGB76) and the genetic environment in which this gene is located. The 12,076 bp lnu(B)-carrying fragment from SGB76 strain contained 11 opening reading frames (ORFs) of at least 100 amino acids (accession number KF772204). Other resistance genes detected in this structure include aadE (streptomycin resistance), spw (spectinoycin resistance), and lsa(E) (pleuromutilin, lincosamide and streptogramin A resistance). Basic Local Alignment Search Tool (BLAST) analysis revealed that this sequence exhibits similarity to other lnu(B)-containing structures previously identified in S. aureus (accession numbers JQ861959 and JX560992) and E. faecalis (accession number AF408195). The region of 5982 bp located upstream the lnu(B) gene in SGB76 is 99 % identical to the structures described in S. aureus and E. faecalis. The lsa(E) 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. During 2008-2013 we received 9 epidemiological unrelated isolates of SGB resistant to clindamycin but susceptible to erythromycin recovered at different hospitals of Buenos Aires. The aim of this study was to evaluate the clonal relationship of these strains and the presence of the genetic element containing the lnu(B) gene, previously described by us. Methods: Nine unrelated S. agalactiae isolates were obtained from different sources. Antibiotic susceptibility was evaluated following CLSI recommendations. All isolates were screened by PCR for ermB, mef and lnu(B) determinants. ApaI- PFGE was performed for clonal assessment. The genetic environment of lnu(B) was mapped in all of the strains, using a PCR- scheme covering the 12,076 kb fragment previously characterized. Results: Susceptibility to erythromycin and resistance to clindamycin were confirmed for all the isolates. Only the lnu(B) gene was positive by PCR and confirmed by DNA sequencing. PCR mapping strategy showed that the 12,076 kb fragment was identical in 8/9 strains. PFGE analysis revealed a single clone associated with this phenotype. Conclusions: The emergence of this lincomycin resistance phenotype at these hospitals is mainly due to the dissemination of one clone carrying lnu(B) gene in the same genetic platform. The description of this multiresistance cluster in S. agalactiae represents another example of resistance genes shared by enterococci, staphylococci and streptococci.