STUDY OF SEROTYPES, SUSCEPTIBILITY TO MACROLIDE AND VIRULENCE AND RESISTANCE MOLECULAR PROFILES IN INVASIVE STRAINS OF Streptococcus agalactiae IN TWO ARGENTINE PROVINCES

LACZESKI M, CANNISTRACI GIOLITO R, LITTVIK A, PAVAN J, NOVOSAK M, PEGELS E, OVIEDO P, QUIROGA M, VERGARA M

Buenos Aires

Simposio; XIX Lancefield; 2014

Asociación Argentina de Microbiología - SADEBAC

A study of invasive strains of Streptococcus agalactiae (GBS) from Cordoba and Misiones wasconducted to determine serotypes, the susceptibility to macrolides and molecular profiles of virulenceand resistance.We studied seventeen strains, 16 of human newborns with invasive disease (10 fromMisiones and 6 from Cordoba) recovered from cerebrospinal fluid (6 strains), blood (9 strains) andcellulite (1 strain) and a strain of trophoblastic remnants from Misiones. The serotypes weredetermined by agglutination with sera (Strep-B Latex Copenhagen S Denmark) and the phenotypesof resistance to macrolide-lincosamide-streptogramin B (MLSB), were determined with the doubledisktest (D-test) on Mueller-Hinton agar with erythromycin (ERY) (15 μg) and clindamycin CLI (2 μg)(Britania, Argentina), 5% of sheep blood. The confirmation was performed by E-test strips providedby Oxoid, UK and Biomerieux, France by ERI and CLI respectively that determined the minimuminhibitory concentration (MIC). Results were interpreted as recommended by the Clinical andLaboratory Standards Institute (CLSI) 2013. Resistance genes were investigated by conventionalPCR: ermB (constitutive methylase-cMLSB), ermTR (inducible methylase-iMLSB) and mefA (effluxmechanism-M phenotype) and and those of virulence encoding: C protein (bac and bca), Rib protein(rib), laminin (lmb), hyaluronidase (hylB), c5a-peptidase (scpB), FbsA and FbsB protein (fbsA andfbsB) and β-hemolysin (cylB). In Cordoba: Serotype III (50%) and Ia (50%) were detected. One strainshowed cMLSB phenotype, confirmed by MIC. The same strains showed a resistance gene ermB. Allstudied virulence genes were detected in 100% of these strains. In Misiones: Serotypes were III(72.7%), Ia (18.2%) and Ib (9.1%). All strains were susceptible to CLI and ERI by D-test, confirmedby MIC. None of the strains showed resistance genes. Virulence genes bca, rib, hylB, lmb, fbsA, fbsBand cylB were detected in 100% of the strains, bac in 81.8 % and scpB in 90.9%. Our results are inaccordance with international data, associating higher frequency of serotype III of invasive neonataldisease followed by Ia. The presence of serotype Ib could indicate a regional difference for Misiones.We highlight the macrolides susceptibility in strains of Misiones and consistency in the results for Dtest,MIC and PCR for the single strain resistant phenotype cMLSB from Cordoba. The virulencegenes studied were presented with high frequency as expected for invasive strains. The bac andscpB genes were detected more frequently in strains from Cordoba, although it is not possible toindicate whether there are statistically significant differences between the two regions due to thesmall sample size. fbsA, fbsB and cylB, genes directly associated with invasive procedures weredetected in 100% of the strains studied. It is noteworthy that in our previous publications withcolonizing strains, bac, bca, rib, lmb and hylB were detected, and there was no birth with GBSdisease, since colonized pregnant women received intrapartum prophylaxis.