In vitro efficacy of amaltas (Cassia fistula L.) against the pathogens causing otitis externa

Introduction and objective: Otitis externa, commonly called ear disease, is characterized by inflammation of the external ear canal. The aim of this study was to evaluate the antimicrobial potential of Cassia fistula flowers, leaves and bark extracts against Staphylococcus aureus, Proteus mirabilis, Escherchia coli, Pseudomonas aeruginosa, Acinetobacter sp., and Candida albicans, pathogens causing otitis externa and their comparison with locally available ear drops. Materials and methods: Methanol, ethanol, acetone, aqueous (hot and cold) extracts from the flowers, leaves and bark of C. fistula were tested for their antimicrobial activity against six ear pathogens causing otitis externa determined by agar well diffusion method. Results: Organic flower and bark extracts displayed activity against all tested ear pathogens whereas leaf extract showed activity against four tested bacteria and aqueous extracts were unable to exhibit any antimicrobial activity. Of the three organic solvents evaluated, acetonic flower extract was found to be best against S. aureus followed by bark extract and leaf extract. The acetonic flower extract showed larger inhibition zones compared to the herbal ear drops with minimum inhibitory concentration (MIC) of 6.25mg/ml. Conclusion: Acetonic extract of C. fistula flower may be used to treat otitis externa especially caused by S. aureus. However, more detailed studies such as in vivo testing and pharmacokinetics properties are needed to determine its therapeutic potential. Significance and impact of the study: Due to antimicrobial effects of amaltas organic extracts on ear pathogens, use of flower acetonic extract in herbal ear drops is recommended.