vanM, a new glycopeptide resistance gene cluster found in Enterococcus faecium.
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 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.
Xu
Xiaogang
X
Institute of Antibiotics, Huashan Hospital, Fudan University, 12 M. Wulumuqi Rd., Shanghai, P. R. China.
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
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002853:Chromatography, Liquid; D024881:Drug Resistance, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D016984:Enterococcus faecium / Q000187:drug effects* / Q000235:genetics*; D006020:Glycopeptides / Q000494:pharmacology*; D013058:Mass Spectrometry; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics / Q000502:physiology; D016133:Polymerase Chain Reaction
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D006020:Glycopeptides