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CARACTERISATION EXHAUSTIVE DES SUBSTITUTIONS
DE PENICILLIN-BINDING PROTEINS INTERVENANT
DANS LA RESISTANCE AUX β-LACTAMINES CHEZ
STREPTOCOCCUS PNEUMONIAE

Abstract : Penicillin-Binding Proteins (PBP) are enzymes catalyzing the final steps of the bacterial cell-wall synthesis and are the targets of the β-lactam antibiotics. There are many amino acid substitutions in PBPs of clinical isolates of Streptococcus pneumoniae resistant to β-lactams, leading to a decrease of the affinity of these enzymes for antibiotics. There are about 40 substitutions in the transpeptidase domain of the two major resistant
determinants PBP2x and PBP1a.
Former studies have described the role of four mutations of PBP2x and three of PBP1a. But these mutations explain only a part of the resistance phenomenon. Only a few mutations may be involved in the loss of affinity of PBPs for β-lactam antibiotics leading to an increase of the resistance level.
To identify all the relevant mutations, a set of automated protocols allowing to do site-directed mutagenesis, expression, purification and functional characterization of enzymes using automated liquid-handling systems was developed. An exhaustive characterization of more than 40 mutants of PBP2x of the highly resistant clinical isolate 5204 was performed using this method. All the relevant substitutions were identified and a new molecular
resistance mechanism to β-lactams was elucidated. Moreover, a functional and phenotypic study of the resistance involving PBP1a was performed.
This work provides a global view on the molecular mechanisms of the PBP-mediated resistance of S.
pneumoniae to β-lactams using an original exhaustive method.
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https://tel.archives-ouvertes.fr/tel-00131811
Contributor : Raphael Carapito <>
Submitted on : Monday, February 19, 2007 - 2:39:32 PM
Last modification on : Thursday, April 23, 2020 - 2:26:26 PM

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  • HAL Id : tel-00131811, version 1

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Raphael Carapito. CARACTERISATION EXHAUSTIVE DES SUBSTITUTIONS
DE PENICILLIN-BINDING PROTEINS INTERVENANT
DANS LA RESISTANCE AUX β-LACTAMINES CHEZ
STREPTOCOCCUS PNEUMONIAE. Biochimie [q-bio.BM]. Université Joseph-Fourier - Grenoble I, 2006. Français. ⟨tel-00131811⟩

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