An Internationally Spread Clone of Streptococcus pneumoniae Evolves from Low-Level to Higher-Level Penicillin Resistance by Uptake of Penicillin-Binding Protein Gene Fragments from Nonencapsulated Pneumococci

Abstract

Low-level penicillin resistance in an international Streptococcus pneumoniae serotype 19F clone emerging in Switzerland was characterized by mutations in the penicillin-binding protein PBP2x. Some isolates of this clone had evolved to higher resistance levels (penicillin MICs of 0.094 and 1 μg/ml), probably by acquisition of pbp2x fragments from local nonencapsulated pneumococci.