Molecular evolution of rifampicin resistance in Streptococcus pneumoniae.

Rifampicin resistance has arisen in several different species of bacteria because of alterations to one or more regions in the target of the antibiotic, the beta-subunit of RNA polymerase encoded by rpoB. Nucleotide sequence analysis of a 270 bp fragment of rpoB from 16 clinical rifampicin-susceptible isolates of Streptococcus pneumoniae, 8 clinical rifampicin-resistant isolates, and 3 spontaneous rifampicin-resistant mutants, has revealed that, as with previously examined species, point mutations within the cluster I region of rpoB, at sites encoding Asp516 and HiS526, also confer resistance to rifampicin in this important human pathogen. Moreover, the residues within cluster I, that were altered within the rifampicin-resistant mutants of S.