Noncanonical vancomycin resistance cluster from Desulfitobacterium hafniense Y51.
The glycopeptide vancomycin is a drug of last resort for infection with gram-positive organisms, and three genes are vital to resistance: vanH, vanA, and vanX. These genes are found in a vanHAX cluster, which is conserved across pathogenic bacteria, glycopeptide antibiotic producers, and other environmental bacteria. The genome sequence of the anaerobic, gram-positive, dehalogenating bacterium Desulfitobacterium hafniense Y51 revealed a predicted vanA homolog; however, it exists in a vanAWK-murFX cluster, unlike those of other vancomycin-resistant organisms. Using purified recombinant VanA from D. hafniense Y51, we determined its substrate specificity and found it to have a 42-fold preference for D-lactate over D-alanine, confirming its activity as a D-Ala-D-Lac ligase and its annotation as VanA. Furthermore, we showed that D. hafniense Y51 is highly resistant to vancomycin, with a MIC for growth of 64 microg/ml. Finally, vanA(Dh) is expressed during growth in vancomycin, as demonstrated by reverse transcription-PCR. This finding represents a new glycopeptide antibiotic resistance gene cluster and expands the genetic diversity of resistance to this important class of antibiotic.
Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street W., Hamilton, Ontario, Canada.
Lindsay
L
Kalan
Sara
S
Ebert
Tom
T
Kelly
Gerard D
GD
Wright
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D045858:Desulfitobacterium / Q000187:drug effects* / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005810:Multigene Family / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020713:Vancomycin Resistance / Q000235:genetics*
D000900:Anti-Bacterial Agents