Correlation between Alterations of the Penicillin-binding Protein 2 and Modifications of the Peptidoglycan Structure in Neisseria meningitidis with Reduced Susceptibility to Penicillin G

Aude Antignac,Ivo G Boneca,Jean-Claude Rousselle,Abdelkader Namane,Jean-Philippe Carlier,Julio A Vázquez,Andrew Fox,Jean-Michel Alonso,Muhamed-Kheir Taha

doi:10.1074/jbc.m304607200

Abstract

Reduced susceptibility to penicillin G in Neisseria meningitidis is directly correlated with alterations in the penA gene, which encodes the penicillin-binding protein 2 (PBP2). Using purified PBP2s from different backgrounds, we confirmed that the reduced susceptibility to penicillin G is associated with a decreased affinity of altered PBP2s for penicillin G. Infrared spectroscopy analysis using isogenic penicillin-susceptible strains and strains with reduced susceptibility to penicillin G suggested that the meningococcal cell wall is also modified in a penA-dependent manner. Moreover, reverse-phase high pressure liquid chromatography and mass spectrometry analysis of these meningococcal strains confirmed the modifications of peptidoglycan components and showed an increase in the peaks corresponding to pentapeptide-containing muropeptides. These results suggest that the D,D-transpeptidase and/or D,D-carboxypeptidase activities of PBP2 are modified by the changes in penA gene.

Highlights

Neisseria meningitidis is an exclusive human bacterium that usually infects the nasopharynx
Because alterations of both penicillin-binding protein 2 (PBP2) and PBP1 are associated with an increased level of penicillin resistance in N. gonorrhoeae [12], we used restriction fragment length polymorphism (RFLP) to analyze the ponA polymorphism in 66 PenS and penicillin G (PenI) meningococcal strains
We showed that the polymorphism in the ponA gene, encoding PBP1, is not associated with the PenI phenotype

Summary

Introduction

Neisseria meningitidis is an exclusive human bacterium that usually infects the nasopharynx. Meningococcal infections are still a major public health concern due to periodic epidemics of meningitis in Africa and local outbreaks in developed countries This concern is heightened by the increasing prevalence of meningococcal strains with reduced susceptibility to penicillin G (PenI), one of the major antibiotics used for the treatment of meningococcal infections. Meningococcal strains with reduced susceptibility to penicillin G (PenI) (MICs between 0.125 and 1 ␮g/ml) have been reported worldwide [9], and this reduction in susceptibility is at least partly due to the decreased affinity of PBP2 encoded by an altered penA gene [10, 11]. Because penicillin binds covalently to PBP2, the alterations around the active site-encoding domain probably reduce the affinity of PBP2 for penicillin G, accounting for the PenI phenotype. The lack of information concerning the structure of the N. meningitidis peptidoglycan has hindered this

Objectives

Results

Conclusion