Evidence for a Clonal Origin of Relative Penicillin Resistance among Type 9L Pneumococci in Northwestern Canada

Abstract

The relationships among capsular type, protein type, and penicillin resistance for capsular group 9 Streptococcus pneumoniae collected in northwestern Canada between 1974 and 1987 were examined. The group 9 relatively penicillin-resistant (RPR) isolates were of the rare 9L capsular type. Of 47 penicillin-susceptible (PS) group 9 isolates that were typed for capsule, only 1 was 9L. Among 29 PS group 9 isolates that were protein typed, 9 protein types were observed. Of the 70 RPR isolates, 51 were protein type P23, 1 was P19, and 18 could not be typed (PO). Protein types P23 differed from PObya single epitope on pneumococcal surface protein A. These results suggest that the Canadian P23 and POcapsular group 9 isolates are likely subclones of a primordial 9L RPR strain.