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Antimicrobial Agents and Chemotherapy, January 2009, p. 242-248, Vol. 53, No. 1
0066-4804/09/$08.00+0 doi:10.1128/AAC.00642-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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Laboratoire de Bactériologie, JE2526, UFR Médecine, Université d'Auvergne, Clermont-Ferrand,1 Laboratoire de Chimie Bactérienne, UPR9043, CNRS, Marseille, France2
Received 16 May 2008/ Returned for modification 2 October 2008/ Accepted 26 October 2008
β-Lactamases represent the major resistance mechanism of gram-negative bacteria against β-lactam antibiotics. The amino acid sequences of these proteins vary widely, but all are located in the periplasm of bacteria. In this study, we investigated the translocation mechanism of representative β-lactamases in an Escherichia coli model. N-terminal signal sequence analyses, antibiotic activity assay, and direct measurement of translocation of a green fluorescent protein (GFP) reporter fused to β-lactamases revealed that most were exported via the Sec pathway. However, the Stenotrophomonas maltophilia L2 β-lactamase was exported via the E. coli Tat translocase, while the S. maltophilia L1 β-lactamase was Sec dependent. These results show the possible Tat-dependent translocation of β-lactamases in the E. coli model system. In addition, the mutation of the cytoskeleton-encoding gene mreB, which may be involved in the spatial organization of penicillin-binding proteins, decreased the MIC of β-lactams for β-lactamase-producing E. coli. These findings provide new knowledge about β-lactamase translocation, a putative new target for addressing β-lactamase-mediated resistance.
Published ahead of print on 3 November 2008.
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