Study on synergistic effect of 2-phenylethanol and clotrimazole on candida species isolated from patients with chronic vulvovaginal candidiasis

Background: 2-phenylethanol is a colorless and aromatic compound with antimicrobial effects which is used extensively in perfumes and cosmetics, as well as in the food industry. Chronic vulvovaginal candidiasis is a vulvovaginal inflammation which is caused by Candida spp. Resistance to clotrimazole which is one of the most common drugs in the treatment of this disease was reported in many patients. In order to improve the treatment, the effect of 2-phenyl ethanol was investigated in combination with clotrimazole on Candida species isolated from chronic vulvovaginal candidiasis. Methods: This interventional study was performed in Iran University of Medical Sciences from February, 2016 until December, 2016 on Candida species isolated from women with chronic candidial vulvovaginitis who had been referred to Lolagar Hospital of Tehran. All specimens were examined by direct microscopy, culturing on Candida CHROMagar medium (to primary identification), sabouraud dextrose agar medium) to preservation the isolates) and determining the internal transcribed spacer (ITS) sequence (in order to final determination of Candida species). Then clotrimazole and 2-phenyl ethanol alone and in combination, was examined on isolated species, according to Clinical and Laboratory Standards Institute (CLSI) M27-A3 protocol (micro-broth dilution method). Finally, findings were analyzed. Results: From 40 detected strains of Candida species in this study, 95% were Candida albicans and 5% were Candida africana. The mean minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of clotrimazole were 24.73±28.87 µg/ml and 30.18±33.004 µg/ml, respectively and the mean MIC and MFC of 2-phenylethanol were 2580±932.38 µg/ml and 3200±1403.29 µg/ml, respectively. The MIC50 and MIC90 of clotrimazole were 16 and 64 µg/ml, respectively. The MIC50 and MIC90 of 2-phenylethanol were both 3200 µg/ml. Most of the isolates were resistant to clotrimazole (82.5%). In combination test, the mean MIC of 2-phenylethanol and clotrimazole alone were 3200±0 µg/ml and 56±40.16 µg/ml, respectively. The fractional inhibitory concentration index (FICI) range was 0.14-0.37. Also, there was a significant difference between clotrimazole MIC values alone and in combination (P= 0.021). Conclusion: The synergistic effect was observed in combination of clotrimazole and 2-phenylethanol.