Mosaic pbpX genes of major clones of penicillin‐resistant Streptococcus pneumoniae have evolved from pbpX genes of a penicillin‐sensitive Streptococcus oralis

Abstract

Penicillin-resistant clinical isolates of Streptococcus pneumoniae contain mosaic penicillin-binding protein (PBP) genes that encode PBPs with decreased affinity for beta-lactam antibiotics. The mosaic blocks are believed to be the result of gene transfer of homologous PBP genes from related penicillin-resistant species. We have now identified a gene homologous to the pneumococcal PBP2x gene (pbpX) in a penicillin-sensitive Streptococcus oralis isolate M3 from South Africa that diverged by almost 20% from pbpX of penicillin-sensitive pneumococci, and a central sequence block of a mosaic pbpX gene of Streptococcus mitis strain NCTC 10712. In contrast, it differed by only 2-4% of the 1 to 1.5 kb mosaic block in pbpX genes of three genetically unrelated penicillin-resistant S. pneumoniae isolates, two of them representing clones of serotype 6B and 23F, which are prevalent in Spain and are also already found in other countries. With low concentrations of cefotaxime, transformants of the sensitive S. pneumoniae R6 strain could be selected containing pbpX genes from either S. mitis NCTC 10712 or S. oralis M3, demonstrating that genetic exchange can already occur between beta-lactam-sensitive species. These data are in agreement with the assumption that PBPs as penicillin-resistance determinants have evolved by the accumulation of point mutations in genes of sensitive commensal species.

Homeologous recombination and mismatch repair during transformation in Streptococcus pneumoniae: saturation of the Hex mismatch repair system.

“…pneumoniae has involved the replacement, presumably by transformation, of (part of) the original sensitive pbp genes by homeologous sequences from unknown related species. In agreement with this proposal, it has been shown recently that S. mitis and S. oralis are likely donors for some of these sequences (30,31).…”

The CiaRH System ofStreptococcus pneumoniaePrevents Lysis during Stress Induced by Treatment with Cell Wall Inhibitors and by Mutations inpbp2xInvolved in β-Lactam Resistance

“…Samples were taken during exponential growth phase, and pictures were taken with a Nikon Eclipse E600 microscope in phase contrast. moniae 8249) and 40 (S. pneumoniae 681) amino acids in the transpeptidase domain, corresponding to 7 to 11% in peptide sequence (46). None of these PBP2x variants contained the mutations present in the laboratory mutant C303.…”

“…In some experiments, CSP was used at a concentration of 100 ng/ml. R6 transformants containing mosaic blocks of the penicillin-resistant clinical isolates S. pneumoniae 8249 (type 19) and 681 (6B) have been described (46). The pbp2x fragments containing the point mutations of the mutants C103 and C203 were amplified by PCR using the oligonucleotide primers 5Ј-A 1501 TCGTTTTAAATTTGG or 5Ј-C 1709 AAATGATC AAACTGC and 5Ј-T 2345 CTGGAACCTCCTCTG according to the sequence available under GenBank accession number X16367, and transformation of the pbp2x mutations into the R6 strain was verified by sequencing of the transformants.…”

The HtrA Protease from Streptococcus pneumoniae Digests Both Denatured Proteins and the Competence-stimulating Peptide

“…The ability to develop competence is critical for the virulence of this organism (1)(2)(3)(4) and has promoted the development of antibiotic resistance (5,6) that now restricts the options available for treating pneumococcal infections. A central component of this process (reviewed in Ref.…”