Mechanisms of penicillin resistance in streptococcus pneumoniae: Targets, gene transfer and mutations

Abstract

Penicillin resistance in Streptococcus pneumoniae has been recognized in the bacterial population 40 years ago and has increased dramatically worldwide ever since. It is based on alterations of the penicillin target enzymes, the penicillin binding proteins (PBPs). In clinical isolates, horizontal gene transfer involving closely related commensal species mediates the acquisition of highly altered PBP genes, resulting in the evolution of complex mosaic structures. The identification of PBP mutations in resistant laboratory mutants has helped to reveal amino acids responsible for the decreased affinity of the target proteins, in addition to high resolution structures of PBPs from resistant clinical isolates. Moreover, non-PBP genes have been discovered that contribute to resistance.