The in-vitro antimicrobial effects of azelaic acid upon Propionibacterium acnes strain P37

The in-vitro antimicrobial activity of azelaic acid, a new topical acne treatment, upon Propionibacterium acnes strain P37 was studied. In phosphate buffer at pH 6.0 500 mM azelaic acid had bactericidal activity whilst the addition of nutrients reduced susceptibility. Bactericidal activity was greatly enhanced by reducing the pH to 5.6. In a simple denned medium growth was inhibited by 100μM azelaic acid. The accumulation of 14C azelaic acid was pH and temperature dependent with maximum uptake occurring at pH 4.6, 30°C. Valinomycin, nigericin and CCCP (membrane-active inhibitors of energy transduction) inhibited uptake and azelaic acid was not accumulated by non-viable cells. The degradation of azelaic acid was repressed by glucose, and acetic acid was the major end-product of azelaic acid degradation in glucose depleted media. The incorporation of radiolabelled precursors into protein, DNA and RNA were inhibited in a dose dependent manner, and 50% inhibition occurred at 313, 3639 and 9226 μM respectively. The synthesis of proteins was shown to be significantly more sensitive to the action of azelaic acid than both RNA and DNA synthesis.