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VanM, a new glycopeptide resistance gene cluster found in Enterococcus faecium.

ABSTRACT: Since glycopeptide-resistant enterococci (GRE) were reported in 1988, they have appeared in hospitals worldwide. Seven van gene cluster types (vanA, vanB, vanC, vanD, vanE, vanG, and vanL) are currently known. We investigated a clinical strain of Enterococcus faecium Efm-HS0661 that was isolated in 2006 from an inpatient with intra-abdominal infection in Shanghai. It was resistant to most antimicrobials, including vancomycin (MIC, >256 ?g/ml) and teicoplanin (MIC, 96 ?g/ml). Glycopeptide resistance could be transferred to E. faecium BM4105RF by conjugation. The donor and its transconjugant were negative by PCR for the known van genes. By cloning and primer walk sequencing, we discovered a novel van gene cluster, designated vanM. The vanM ligase gene was 1,032-bp in length and encoded a 343-amino-acid protein that shared 79.9, 70.8, 66.3, and 78.8% amino acid identity with VanA, VanB, VanD, and VanF, respectively. Although the vanM DNA sequence was closest to vanA, the organization of the vanM gene cluster was most similar to that of vanD. Upstream from the vanM cluster was an IS1216-like element, which may play a role in the dissemination of this resistance determinant. Liquid chromatography-mass spectrometry analysis of peptidoglycan precursors extracted from the VanM-type strain Efm-HS0661 treated with vancomycin or teicoplanin revealed a modified precursor (UDP-N-acetylmuramic acid [MurNAc]-tetrapeptide-D-Lac), indicating that VanM, like VanA, confers glycopeptide resistance by the inducible synthesis of precursor ending in D-Ala-D-Lac.

SUBMITTER: Xu X

PROVIDER: S-EPMC2976141 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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vanM, a new glycopeptide resistance gene cluster found in Enterococcus faecium.

Xu Xiaogang X Lin Dongfang D Yan Guoquan G Ye Xinyu X Wu Shi S Guo Yan Y Zhu Demei D Hu Fupin F Zhang Yingyuan Y Wang Fu F Jacoby George A GA Wang Minggui M

Antimicrobial agents and chemotherapy 20100823 11

Since glycopeptide-resistant enterococci (GRE) were reported in 1988, they have appeared in hospitals worldwide. Seven van gene cluster types (vanA, vanB, vanC, vanD, vanE, vanG, and vanL) are currently known. We investigated a clinical strain of Enterococcus faecium Efm-HS0661 that was isolated in 2006 from an inpatient with intra-abdominal infection in Shanghai. It was resistant to most antimicrobials, including vancomycin (MIC, >256 μg/ml) and teicoplanin (MIC, 96 μg/ml). Glycopeptide resista ...[more]

PMID: 20733041

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Project description:A new open reading frame, encoding a putative integrase-like protein, was detected downstream from the six genes of the vanD glycopeptide resistance cluster in Enterococcus faecium BM4339 (B. Casadewall and P. Courvalin, J. Bacteriol. 181:3644-3648, 1999). In this cluster, genes coding for the VanR(D)-VanS(D) two-component regulatory system were cotranscribed from the P(R(D)) promoter, whereas transcription of the vanY(D), vanH(D), vanD, vanX(D), and intD genes was initiated from the P(Y(D)) promoter located between vanS(D) and vanY(D) (the D subscript indicates that the gene is part of the vanD operon). The VanR(D)-VanS(D) regulatory system is likely to activate transcription of the resistance genes from the promoter P(Y(D)). Glycopeptide-susceptible derivatives of BM4339 were obtained by trans complementation of the frameshift mutation in the ddl gene, restoring functional D-alanine:D-alanine ligase activity in this strain. The glycopeptide-susceptible transformant BM4409, producing only D-alanyl-D-alanine-terminating peptidoglycan precursors, did not express the resistance genes encoding the VanY(D) D,D-carboxypeptidase, the VanH(D) dehydrogenase, the VanD ligase, the VanX(D) D,D-dipeptidase, and also the IntD integrase, although the regulatory region of the vanD cluster was still transcribed. In BM4409, the absence of VanR(D)-VanS(D), apparently dependent, transcription from promoter P(Y(D)) correlated with the lack of D-alanyl-D-lactate-terminating precursors. The vanX(D) gene was transcribed in BM4339, but detectable amounts of VanX(D) D,D-dipeptidase were not synthesized. However, the gene directed synthesis of an active enzyme when cloned on a multicopy plasmid in Escherichia coli, suggesting that the enzyme was unstable in BM4339 or that it had very low activity that was detectable only under conditions of high gene dosage. This activity is not required for glycopeptide resistance in BM4339, since this strain cannot synthesize D-alanyl-D-alanine.

Dataset Information

VanM, a new glycopeptide resistance gene cluster found in Enterococcus faecium.

Publications

vanM, a new glycopeptide resistance gene cluster found in Enterococcus faecium.

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