This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Comenge, Y. Articles by Arthur, M. Search for Related Content PubMed PubMed Citation Articles by Comenge, Y. Articles by Arthur, M.

The CroRS Two-Component Regulatory System Is Required for Intrinsic ß-Lactam Resistance in Enterococcus faecalis

INSERM E0004-LRMA, UFR Broussais-Hôtel Dieu, Université Paris VI, 75270 Paris,¹ Département Régulations, Développement et Diversité Moléculaire, Museum National d'Histoire Naturel, USM0502-CNRS UMR8041, 75005 Paris,France,⁴ University of Massachusetts Dartmouth, North Dartmouth, Massachusetts 02747,² Department of Emergency Medicine, Somerville Hospital, Harvard Medical School, Somerville, Massachusetts 02143³

Received 30 May 2003/ Accepted 17 September 2003

Enterococcus faecalis produces a specific penicillin-binding protein (PBP5) that mediates high-level resistance to the cephalosporin class of ß-lactam antibiotics. Deletion of a locus encoding a previously uncharacterized two-component regulatory system of E. faecalis (croRS) led to a 4,000-fold reduction in the MIC of the expanded-spectrum cephalosporin ceftriaxone. The cytoplasmic domain of the sensor kinase (CroS) was purified and shown to catalyze ATP-dependent autophosphorylation followed by transfer of the phosphate to the mated response regulator (CroR). The croR and croS genes were cotranscribed from a promoter (croRp) located in the rrnC-croR intergenic region. A putative seryl-tRNA synthetase gene (serS) located immediately downstream from croS did not appear to be a target of CroRS regulation or to play a role in ceftriaxone resistance. A plasmid-borne croRp-lacZ fusion was trans-activated by the CroRS system in response to the presence of ceftriaxone in the culture medium. The fusion was also induced by representatives of other classes of ß-lactam antibiotics and by inhibitors of early and late steps of peptidoglycan synthesis. The croRS null mutant produced PBP5, and expression of an additional copy of pbp5 under the control of a heterologous promoter did not restore ceftriaxone resistance. Deletion of croRS was not associated with any defect in the synthesis of the nucleotide precursor UDP-MurNAc-pentapeptide or of the D-Ala₄L-Ala-L-Ala-Lys₃ peptidoglycan cross-bridge. Thus, the croRS mutant was susceptible to ceftriaxone despite the production of PBP5 and the synthesis of wild-type peptidoglycan precursors. These observations constitute the first description of regulatory genes essential for PBP5-mediated ß-lactam resistance in enterococci.

This article has been cited by other articles:

• Le Breton, Y., Muller, C., Auffray, Y., Rince, A. (2007). New Insights into the Enterococcus faecalis CroRS Two-Component System Obtained Using a Differential-Display Random Arbitrarily Primed PCR Approach. Appl. Environ. Microbiol. 73: 3738-3741 [Abstract] [Full Text]  
• Calvez, S., Rince, A., Auffray, Y., Prevost, H., Drider, D. (2007). Identification of new genes associated with intermediate resistance of Enterococcus faecalis to divercin V41, a pediocin-like bacteriocin. Microbiology 153: 1609-1618 [Abstract] [Full Text]  
• Depardieu, F., Podglajen, I., Leclercq, R., Collatz, E., Courvalin, P. (2007). Modes and Modulations of Antibiotic Resistance Gene Expression. Clin. Microbiol. Rev. 20: 79-114 [Abstract] [Full Text]  
• de Been, M., Francke, C., Moezelaar, R., Abee, T., Siezen, R. J. (2006). Comparative analysis of two-component signal transduction systems of Bacillus cereus, Bacillus thuringiensis and Bacillus anthracis.. Microbiology 152: 3035-3048 [Abstract] [Full Text]  
• Muller, C., Le Breton, Y., Morin, T., Benachour, A., Auffray, Y., Rince, A. (2006). The Response Regulator CroR Modulates Expression of the Secreted Stress-Induced SalB Protein in Enterococcus faecalis.. J. Bacteriol. 188: 2636-2645 [Abstract] [Full Text]  
• Bourgogne, A., Hilsenbeck, S. G., Dunny, G. M., Murray, B. E. (2006). Comparison of OG1RF and an Isogenic fsrB Deletion Mutant by Transcriptional Analysis: the Fsr System of Enterococcus faecalis Is More than the Activator of Gelatinase and Serine Protease.. J. Bacteriol. 188: 2875-2884 [Abstract] [Full Text]  
• Hancock, L. E., Perego, M. (2004). Systematic Inactivation and Phenotypic Characterization of Two-Component Signal Transduction Systems of Enterococcus faecalis V583. J. Bacteriol. 186: 7951-7958 [Abstract] [Full Text]