In-vitro potential of crude extracts of selected garden herbs for mastitis management in Zambia

Abstract

Introduction: The advent of bovine mastitis associated antimicrobial resistance has necessitated development of alternative herbal remedies. In this study, we tested, in-vitro, the antimicrobial efficacy of three crude extracts: (1) aqueous, (2) ethanol and (3) ethyl acetate extracts of Zambian cultivated Aloe barbadensis Miller (Aloe vera) and Curcuma longa (Turmeric) and also made comparisons to synthetic anti-mastitis formulations. Methods: The active compounds of these herbs were obtained as crude extracts using water, ethanol and ethyl acetate as solvents. The test microbes comprised of ten standard controls including Escherichia coli and Pseudomonas aeruginosa and 84 field isolates (all gram positive bacteria) from clinical and subclinical mastitis milk samples from selected districts of the Southern Province of Zambia belonging to the genera Staphylococcus, Streptococcus, Bacillus and Lactobacillus. The agar dilution method was used to determine the antimicrobial activity by observing the sensitivity which was graded as sensitive, intermediate or resistant. Commercial synthetic anti-mastitis preparations served as positive controls and their sensitivity was compared to that of the herbal preparations. The Minimum Inhibitory Concentrations (MIC) of the herbal formulation was also determined using two-fold serial dilutions. Results: The agar dilution test results of the field isolates indicated 18.8% resistance, 25.3% intermediate and 56% sensitivity for the herbal extracts, while the synthetic anti-mastitis preparation averaged 16.8% resistance, 4.75% intermediate and 78.5% sensitivity. The gram negative controls tested were generally resistant. On average, the agar dilution trials revealed; 41.8% resistance, 13% intermediate and 45.3% sensitivity for the herbal formulation while the synthetic antimicrobials produced 23.5% resistance, 5.2% intermediate and 71.3% sensitivity. Mean MIC was 11.5mg/ml at the 5% serial dilution for the herbal extract compared to the Cephalexin (semi-synthetic antimicrobial) MIC for S. aureus at 0.5mg/L or 0.0005mg/ml. Conclusion: The herbs Aloe vera and Curcuma longa from Zambia showed antimicrobial efficacy on bovine mastitis causing microbes and may be used as a cheaper alternative to synthetic anti-mastitis preparations and as an aid to fight antimicrobial resistance to the benefit of the most affected and resource limited small-scale dairy farmers.