Studies of Antimicrobial Properties of Indigenous Medicinal Plants on Escherichia Coli O157:H7 Isolated from Cattle Faeces
Ozuruonye, C. M.
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The antimicrobial properties of indigenous medicinal plants Azadirachta indica (Neem seeds), Vernonia amygdalina Linn (Bitter leaves), Ocimum gratissimum linn (Scent leaves), Moringa oleifera seeds, Zingiber officinale (Ginger), Allium sativum (Garlic), Pterocapus santalinoides (Nturukpa) against Escherichia coli O157:H7 isolated from cattle faeces was investigated. Escherichia coli O157:H7 used in the study were isolated using CefiximePottasium Tellurite Sorbitol McConkey Agar supplemented with 4 methyl umbelliferyl –β-Dglucuronide (MUG). The colourless white colony isolates were subjected to several biochemical tests and a confirmatory test using immunological latex reagent O157:H7 antiserum to detect agglutination. Antimicrobial susceptibility test on the Escherichia coli O157:H7 was done using Kirby-Bauer method employing the disk diffusion technique for conventional antibiotics and well in agar method for the plant extracts. Extended Spectrum Beta Lactamase production was tested using Double Disk Synergy Test. Phytochemical screening shows that all plant parts contain a wide range of secondary metabolites belonging to classes as tannins, saponins, flavonoids, alkaloids etc. The susceptibility of Escherichia coli O157:H7 isolates to the plant extracts reveals that Escherichia coli O157:H7 used in this study were susceptible to Allium sativum clove (methanolic extract), Moringa oleifera seed (ethanolic extract), Vernonia amygdalina leaf (ethanolic extract) and Pterocarpus santalinoides leaf (Ethanolic extract) in varying degrees and their mean zone of inhibition were 9.8 ± 0.05mm, 8.93 ± 0.03mm, 7.53 ± 0.04mm and 6.0 ± 0.04mm respectively. Susceptibility of the isolates to the extracts were in the order Allium sativum>Moringa oleifera >Vernonia amygdalina > Pterocarpus santalinoides. Whereas crude extracts of Azadrichta indica, Zingiber officinale and Occimum gratissum showed no visible inhibitory effects on Escherichia coli O157:H7. The Minimum Inhibitory Concentration (MIC) of the extracts on Escherichia coli O157:H7 ranged from 6.25mg/ml -50mg/ml in the different extracts. Minimum Bactericidal Concentration (MBC) of extracts on Escherichia coli O157:H7 used in this study showed concentration range of 12.5mg/ml-50mg/ml. Results obtained in this study were analysed using SPSS-Statistics and Excel. The results obtained in this study revealed that ethanol and methanol were the best solvent for the extraction of active constituents of the plants used in the study. The demonstration of antimicrobial activity of crude extracts of A. sativum, P. santalinoides, V. amygdalina and M. oleifera extracts on Escherichia coli O157:H7 is an indication that these plants have antimicrobial properties and therefore are potential sources for drugs with better mode of action. Also the presence of ESBL producers also showed that the overuse, misuse and abuse of antimicrobial agents in human infection and agricultural sector will continually pose limited therapeutic options.