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Cefotaxime resistance in laboratory mutant C604 of Streptococcus pneumoniae, for which the MIC is 1.5 microg/ml, is independent of alterations in high-molecular-mass penicillin-binding protein (PBP) 1a. Instead, a point mutation in PBP 3, the D,D-carboxypeptidase of this organism, caused a reduced affinity for penicillin and contributed to the decreased susceptibility. The mutation Thr-242 to Ile was located directly adjacent to the triad Lys-239-Thr-Gly, a position known to be important for beta-lactam interaction with high-molecular-mass PBPs and beta-lactamases. This mutation was absent in the PBP 3's of four genetically distinct clinical isolates resistant to high levels of penicillin. None of the pbp3 genes had a mosaic structure, but in three cases there was evidence for a site-specific recombination event within a BOX element immediately downstream of pbp3.

Citation

J Krauss, R Hakenbeck. A mutation in the D,D-carboxypeptidase penicillin-binding protein 3 of Streptococcus pneumoniae contributes to cefotaxime resistance of the laboratory mutant C604. Antimicrobial agents and chemotherapy. 1997 May;41(5):936-42

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PMID: 9145848

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