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.
Kalan
Lindsay
L
Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street W., Hamilton, Ontario, Canada.
Ebert
Sara
S
Kelly
Tom
T
Wright
Gerard D
GD
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