Effect of Geographic Disparity on the Antimicrobial Efficacy of Indigenous Plant Extracts Against Vibrio cholerae

Abstract

This study was carried out to investigate the antimicrobial efficacy of methanolic extracts from six medicinal plants including Amomum subulatum (Badi Elaichi), Cinnamomum cassia (sweet wood), Eucalyptus camaldulensis (Murray red gum), Lagenaria siceraria (Bottle gourd/Lauki), Mentha spicata (Spearmint) and Zingiber officinale (Ginger/Adrak) against Vibrio cholerae. Different dilutions (15 mg/ml, 12.5 mg/ml, 10 mg/ml, 7.5 mg/ml, and 5mg/ml) of these extracts were prepared and tested against said strains. Considerable antimicrobial activity was noted in the extracts from all tested plants, with various spectrums of activity. Mentha spicata showed antimicrobial activity against three clinically isolated Vibrio cholera O1 (AMBL1), V. cholera O139 (AMBL2), and V. cholera Wild type (AMBL3). Quantitatively, Mentha spicata exhibited a 3.6 mm zone against the AMBL1 strain, Zingiber officinale (3.1 mm) against the AMBL3 strain, Cinnamomum cassia (2.9 mm) against the AMBL3 strain, and Eucalyptus camaldulensis (2.9 mm) against AMBL2 strain at the concentration of 15mg/ml. Methanolic extract of the minimum inhibitory concentration (MIC) and minimum bacteriostatic concentration (MBC) value of Mentha spicata was found to be 1.5 mg/ml against AMBL3 strain, followed by the extracts of Cinnamomum cassia against AMBL2 and AMBL1 strain, and extracts of Lagenaria siceraria against AMBL2. The extracts of Cinnamomum cassia expressed MIC 1.75 and 2.3 mg/ml, and MBC 1.79 and 2.4 mg/ml against AMBL2 and AMBL1 respectively, while extracts of Lagenaria siceraria were efficient against the AMBL2 strain of Vibrio cholerae with MIC and MBC value of 2.1 mg/ml. There was a significant linear correlation between the efficacy of extracts against vibrio spp. and the site of their sampling. Topographically, the higher the altitude of the collection site of the plant, the lower the efficacy. Antimicrobial efficacy was correlated with geo-environmental location and exposure of tested plants. The geographic correlation of samples to the efficacy against vibrio strain is the first of its kind and provides a baseline to extend the trials for other notorious agents like Mycobacterium tuberculosis, a communicable pathogen of this region.