Significance of the d-Serine-Deaminase and d-Serine Metabolism of Staphylococcus saprophyticusfor Virulence

ABSTRACTStaphylococcus saprophyticusis the only species of Staphylococcusthat is typically uropathogenic and possesses a gene coding for a d-serine-deaminase (DsdA). As d-serine is prevalent in urine and toxic or bacteriostatic to many bacteria, it is not surprising that the d-serine-deaminase gene is found in the genome of uropathogens. It has been suggested that d-serine-deaminase or the ability to respond to or to metabolize d-serine is important for virulence. For uropathogenic Escherichia coli(UPEC), a high intracellular d-serine concentration affects expression of virulence factors. S. saprophyticusis able to grow in the presence of high d-serine concentrations; however, its d-serine metabolism has not been described. The activity of the d-serine-deaminase was verified by analyzing the formation of pyruvate from d-serine in different strains with and without d-serine-deaminase. Cocultivation experiments were performed to show that d-serine-deaminase confers a growth advantage to S. saprophyticusin the presence of d-serine. Furthermore, in vivocoinfection experiments showed a disadvantage for the ?dsdAmutant during urinary tract infection. Expression analysis of known virulence factors by reverse transcription-quantitative PCR (RT-qPCR) showed that the surface-associated lipase Ssp is upregulated in the presence of d-serine. In addition, we show that S. saprophyticusis able to use d-serine as the sole carbon source, but interestingly, d-serine had a negative effect on growth when glucose was also present. Taken together, d-serine metabolism is associated with virulence in S. saprophyticus, as at least one known virulence factor is upregulated in the presence of d-serine and a ?dsdAmutant was attenuated in virulence murine model of urinary tract infection.