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Mosaic pbpX genes of major clones of penicillin‐resistant Streptococcus pneumoniae have evolved from pbpX genes of a penicillin‐sensitive Streptococcus oralis
Author(s) -
Sibold Claus,
Henrichsen Jørgen,
König Andrea,
Martin Christiane,
Chalkley Lynda,
Hakenbeck Regine
Publication year - 1994
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1994.tb01089.x
Subject(s) - biology , streptococcus pneumoniae , streptococcus oralis , penicillin , gene , microbiology and biotechnology , streptococcus , penicillin resistance , genetics , virology , antibiotics , bacteria
Summary Penicillin‐resistant clinical isolates of Streptococcus pneumoniae contain mosaic penicillin‐binding protein (PBP) genes that encode PBPs with decreased affinity for β‐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 β‐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.