Molecular characterization of erythromycin-resistant clinical isolates of the four major antimicrobial-resistant Spanish clones of Streptococcus pneumoniae (Spain23F-1, Spain6B-2, Spain9V-3, and Spain14-5)

Erythromycin resistance and the characterization of the corresponding determinants of resistance were studied in clinical Streptococcus pneumoniae isolates belonging to the four major multiresistant pneumococcal Spanish clones (ermB and mefA genes for the Spain(23F)-1, Spain(9V)-3, serotype 14 variant of the Spain(9V)-3 and Spain(14)-5 clones and ermB gene for the Spain(6B)-2 clone). These isolates were confirmed as major clones by pulsed-field gel electrophoresis (PFGE), BOX-PCR, and multilocus sequence typing (MLST). The spread and prevalence of these erythromycin-resistant variants of the Spanish clones in an area of the north of Spain were dissimilar-low for the Spain(9V)-3 clone (5.8% among the isolates belonging to this clone, including isolates of the serotype 14 variant) and very frequent for the Spain(14)-5 clone (91.7%).