Cloning of the Staphylococcus aureus ddh gene encoding NAD+-dependent D-lactate dehydrogenase and insertional inactivation in a glycopeptide-resistant isolate.
The mechanism of low-level glycopeptide resistance among staphylococci is not known. A cytoplasmic protein, provisionally called Ddh (W. M. Milewski, S. Boyle-Vavra, B. Moreira, C. C. Ebert, and R. S. Daum, Antimicrob. Agents Chemother. 40:166-172, 1996), and the RNA transcript that contains the ddh gene, which encodes Ddh, are present in increased amounts in a vancomycin-resistant isolate, 523k, compared with the susceptible parent isolate, 523. Sequence analysis had previously revealed that Ddh is related to NAD+-dependent D-lactate dehydrogenase (D-nLDH) and VanH. This latter protein is essential for high-level glycopeptide resistance in Enterococcus faecium and Enterococcus faecalis by synthesizing the D-lactate needed for biosynthesis of D-lactate-terminating peptidoglycan precursors with low affinity for vancomycin. We now provide the direct evidence that the ddh gene product is Staphylococcus aureus D-nLDH and hereafter refer to the protein as D-nLDH. However, overproduction of this protein in isolate 523k did not result in production of D-lactate-containing peptidoglycan precursors, and susceptibility testing of ddh mutants of 523k demonstrated that S. aureus D-nLDH is not necessary for glycopeptide resistance in this isolate. We conclude that the mechanism of glycopeptide resistance in this isolate is distinct from that in enterococci.
Boyle-Vavra
S
S
Department of Pediatrics, University of Chicago, Illinois 60637, USA. sboyleva@midway.uchicago.edu
de Jonge
B L
BL
Ebert
C C
CC
Daum
R S
RS
D000429:Alcohol Oxidoreductases / Q000235:genetics*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D003001:Cloning, Molecular; D004352:Drug Resistance, Microbial / Q000235:genetics; D005798:Genes, Bacterial; D007770:L-Lactate Dehydrogenase; D045022:Lactate Dehydrogenases; D016254:Mutagenesis, Insertional; D013211:Staphylococcus aureus / Q000235:genetics*; D017334:Teicoplanin / Q000494:pharmacology; D014640:Vancomycin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C070700:VanH protein, Enterococcus faecium; D017334:Teicoplanin; D014640:Vancomycin; D000429:Alcohol Oxidoreductases; D045022:Lactate Dehydrogenases; D007770:L-Lactate Dehydrogenase; C071195:D-lactate dehydrogenase; C021379:D-2-hydroxyacid dehydrogenase