Antibacterial Agents  


  HEADProf. COURVALIN Patrice / pcourval@pasteur.fr
  MEMBERSDr. GALIMAND Marc / Dr. GRILLOT-COURVALIN Catherine / Prof. LAMBERT Thierry
Dr MOUBARECK Carole / COYNE Sébastien / FOUCAULT Marie-Laure / Dr MEZIANE-CHERIF Djalal
Dr. DEPARDIEU Florence / Dr. PERICHON Bruno / THOMAS Lucie / BREMONT Sylvie
DUPECHEZ Marine / GOUSSARD Sylvie / LEMIRE Astrid / MURGUET Sylvie / SITBON Pascale


  Annual Report

The Unité des Agents Antibactériens studies the genetic basis, biochemical mechanisms, heterologous expression, evolution, and dissemination of antibiotic resistance in bacteria pathogenic for humans

Antibiotic resistance by modulation of gene expression. Vancomycin resistance by remodeling of peptidoglycan synthesis in Gram-positive cocci and intrinsic multidrug-resistance in Acinetobacter by efflux are under the control of two-component systems. We are studying constitutive and drug-dependent clinical isolates selected under therapy that are mutated in the sensor or in the regulator as well as a new tri-component regulatory system in Enterococcus. We are also developing a biochip for the detection of multiple resistance in Acinetobacter by overexpression of efflux systems.

Biological cost and dissemination of vancomycin resistance. We are evaluating, in vitro and in vivo, the biological cost of vancomycin resistance in Enterococcus and the consequence on its dissemination. A dual bioluminescence system will allow comparison of the isogenic strains constructed. Vancomycin resistance in methicillin-resistant Staphylococcus aureus (MRSA) is due to acquisition of the vanA operon from Enterococcus. A partially vancomycin dependent VanA-type methicillin resistant Staphylococcus aureus is currently under study.

Aminoglycoside resistance by ribosomal 16S rRNA methylation. We have detected high-level resistance to all clinically available aminoglycosides in enterobacteria and demonstrated that this was due to methylation of the N7 position of nucleotide G1405 in the 16S rRNA that blocks aminoglycoside binding by ribosomes. Crystals of two methylases are being studied. The gene for a methylase is borne by a plasmid which also confers resistance to fluoroquinolones by efflux. The latter represents a new transferable resistance mechanism to this class of drugs.

Resistance island in Pseudomonas aeruginosa. We are completing the characterization of a genomic island conferring multidrug resistance in P. aeruginosa. Indirect congruent evidence suggests that this island is the progenitor of that in epidemic Salmonella typhimurium DT104.

Gene and protein transfer from an E. coli derived bacterial vector to mammalian cells. Recent development has dealt with cell delivery of large (> 150 kb) bacterial artificial chromosomes. Protein delivery is exploited for stimulation of mucosal immunity in vaccines delivered by the nasal route.

Centre National de Référence des Antibiotiques (CRAB). The public health missions of the CRAB, assigned by the French Health Ministry, consist in the maintenance of strain collections, evaluation of the activity of new antibiotics, the development of reference in vitro susceptibility tests, and the contribution to surveillance of resistance.

Keywords: bacteriology, antibiotics, resistance, gene transfer, infectious diseases

Aab.jpg

Picture 1 : Antibiogram of a Klebsiella pneumoniae harbouring the armA gene. The ArmA protein confers resistance to amikacin, netilmicin, tobramycin, gentamicin, kanamycin and fortimicin, but not to neomycin and apramycin. Picture 2 : Phase contrast (A) and confocal green-fluorescence (B) microscopy examination of VanB-type Enterococcus faecalis and of a constitutive derivative. Bacteria were grown in liquid medium without antibiotic (no glycopeptide) or containing vancomycin or teicoplanin.



  Publications

Marchand, I., L. Damier-Piolle, P. Courvalin, and T. Lambert. 2004. Expression of the RND-type efflux pump AdeABC in Acinetobacter baumannii is regulated by the AdeRS two-component system. Antimicrob. Agents Chemother. 48 : 3298-3304.

Gonzalez-Zorn, B., J.P.M. Senna, L. Fiette, S. Shorte, A. Testard, M. Chignard, P. Courvalin, and C. Grillot-Courvalin. 2005. Bacterial and host factors implicated in nasal carriage of methicillin-resistant Staphylococcus aureus in mice. Infect. Immun. 73 : 1847-1851.

Depardieu, F., P. Courvalin, and A. Kolb. 2005. DNA-binding sites of phosphorylated VanRB and σ70 RNA polymerase in the vanB vancomycin resistance operon of Enterococcus faecium BM4524. Mol. Microbiol. 57 : 550-564.

Liou, F.G., S. Yoshizawa, P. Courvalin, and M. Galimand. 2006. Aminoglycoside resistance by ArmA-mediated ribosomal 16S methylation in human bacterial pathogens. J. Mol. Biol. 359 : 358-364.

Périchon, B., P. Courvalin, and M. Galimand. 2007. Transferable resistance to aminoglycosides by methylation of G1405 in 16S rRNA and to hydrophilic fluoroquinolones by QepA-mediated efflux in Escherichia coli. Antimicrob. Agents Chemother. 51 : 2464-2469.



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Activity Reports 2007 - Institut Pasteur
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