Antimicrobial Effects of Azadirachta indica and Vachellia nilotica Resin Extracts on Streptococcus mutans and Candida albicans isolated from Dental Plaque

Abstract

This study evaluated the antimicrobial efficacy of ethanolic and aqueous extracts of Azadirachta indica and Vachellia nilotica against Streptococcus mutans and Candida albicans, key pathogens involved in dental caries and oral candidiasis. Sixty dental caries patient samples were cultured, with 44 positives for S. mutans and 5 for C. albicans. Both plants’ ethanolic extracts demonstrated significantly greater antimicrobial activity compared to their aqueous counterparts, as evidenced by larger zones of inhibition and lower minimum inhibitory concentrations (MIC) and minimum bactericidal/fungicidal concentrations (MBC/MFC). For S. mutans, the MIC and MBC of ethanolic extracts ranged from 0.4 to 0.8 µg/ml and 0.8 to 1.6 µg/ml, respectively, whereas aqueous extracts showed higher MIC/MBC values. Similarly, against C. albicans, ethanolic extracts exhibited MIC and MFC values between 0.4 and 0.8 µg/ml, outperforming aqueous extracts which required concentrations up to 6.4 µg/ml. These findings indicate that bioactive compounds such as nimbidin and azadirachtin, more effectively extracted in ethanol, contribute to the potent antimicrobial effects. This study supports the traditional use of A. indica and V. nilotica in oral health and highlights their potential as natural alternatives for managing dental infections.