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Antimicrobial Agents and Chemotherapy, September 1998, p. 2215-2220, Vol. 42, No. 9
Department of Biochemistry, McMaster
University, Hamilton, Ontario, Canada L8N
3Z5,1 and
Department of Biological
Chemistry and Molecular Pharmacology, Harvard Medical School,
Boston, Massachusetts 021152
Received 12 December 1997/Returned for modification 10 February
1998/Accepted 15 June 1998
The mechanism of high-level resistance to vancomycin in enterococci
consists of the synthesis of peptidoglycan terminating in
D-alanyl-D-lactate instead of the usual
D-alanyl-D-alanine. This alternate cell wall
biosynthesis pathway is ensured by the collective actions of three
enzymes: VanH, VanA, and VanX. The origin of this resistance mechanism
is unknown. We have cloned three genes encoding homologs of VanH, VanA,
and VanX from two organisms which produce glycopeptide antibiotics: the
A47934 producer Streptomyces toyocaensis NRRL 15009 and the
vancomycin producer Amycolatopsis orientalis C329.2. The
predicted amino acid sequences are highly similar to those found in
VRE: 54 to 61% identity for VanH, 59 to 63% identity for VanA, and 61 to 64% identity for VanX. Furthermore, the orientations of the genes,
vanH, vanA, and vanX, are identical
to the orientations found in vancomycin-resistant enterococci. Southern
analysis of total DNA from other glycopeptide-producing organisms,
A. orientalis 18098 (chloro-eremomycin producer), A. orientalis subsp. lurida (ristocetin producer), and
Amycolatopsis coloradensis subsp. labeda
(teicoplanin and avoparcin producer), with a probe derived from the
vanH, vanA, and vanX cluster from A. orientalis C329.2 revealed cross-hybridizing DNA in all
strains. In addition, the vanH, vanA,
vanX cluster was amplified from all glycopeptide-producing organisms by PCR with degenerate primers complementary to conserved regions in VanH and VanX. Thus, this gene
sequence is common to all glycopeptide producers tested. These results
suggest that glycopeptide-producing organisms may have been the
source of resistance genes in vancomycin-resistant enterococci.
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Glycopeptide Antibiotic Resistance Genes in
Glycopeptide-Producing Organisms
*
Corresponding author. Mailing address: Department of
Biochemistry, McMaster University, 1200 Main St. W, Hamilton, ON,
Canada L8N 3Z5. Phone: (905) 525-9140, ext. 22943. Fax: (905) 522-9033. E-mail: wrightge{at}fhs.csu.mcmaster.ca.
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