Clonal diversity among erythromycin-resistant beta-haemolytic Streptococcus isolates in La Rioja, Spain

Analysis of phenotype, genotype and serotype distribution in erythromycin-resistant group B streptococci isolated from vaginal flora in Southern Ireland

The screening of 2000 women of childbearing age in Cork between 2004 and 2006 produced 37 erythromycin-resistant group B streptococcus (GBS) isolates. PCR analysis was performed to determine the basis for erythromycin resistance. The ermTR gene was most frequently expressed (n=19), followed by the ermB gene (n=8). Four isolates harboured the mefA gene. Six isolates yielded no PCR products. Some phenotype–genotype correlation was observed. All isolates expressing the mefA gene displayed the M phenotype whilst all those expressing ermB displayed the constitutive macrolide resistance (cMLSB) phenotype. Of 19 isolates that expressed the ermTR gene, 16 displayed the inducible macrolide resistance (iMLSB) phenotype. Serotype analysis revealed that serotypes III and V predominated in these isolates. The identification of two erythromycin-resistant serotype VIII isolates among this collection represents the first reported finding of erythromycin resistance in this serotype. A single isolate was non-typable using two latex agglutination serotyping kits.

Multicenter study of the mechanisms of resistance and clonal relationships of Streptococcus agalactiae isolates resistant to macrolides, lincosamides, and ketolides in Spain

Macrolide, lincosamide, and ketolide mechanisms of resistance and clonal relationships were characterized in a collection of 79 resistant group B streptococcus isolates obtained from neonates or pregnant women. The erm(B), erm(TR), and mef(A) genes were present in 62%, 30.4%, and 3.8% of the isolates, respectively. There was considerable clonal diversity among them.