Antibacterial activity of honey and medicinal plant extracts against Gram negative microorganisms

Abstract

There has been a steady rise in antibiotic resistance of bacteria and this urgently calls for the discovery of alternative therapeutic agents. Honey possesses therapeutic potentials which includes antimicrobial activity. Although the antimicrobial activity of honey has been effectively established against an extensive spectrum of microorganisms, it differs depending on the type of honey. To date, not much extensive studies of the antibacterial properties of South African honeys on enteric microorganisms have been conducted. The objective of this study was to compare the antibacterial activity of extracts of six different honeys with those of medical plants commonly used in South Africa. Using a broth dilution method, the antibacterial activity extracts of six South African honeys and medicinal plants against six enteric microorganisms viz- Enterobacter cloacae, Escheriachia coli, Klebsiella pneumoniae, Citrobacter freundii isolated from geophagia samples and Aeromonas hydrophila and plesiomonas isolated both from stool and water samples using agar well diffusion method was done. Different concentrations of honey and plant extracts were tested against each type of microorganism. Briefly, two-fold dilutions of honey solutions were tested to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against each type of microorganism. Extracts from both South African honeys and medicinal plants showed zones of inhibition that ranged from 6.94 to 37.94 mm. The most susceptible bacteria were Escheriachia coli, Aeromonas hydrophila and Plesiomonas shigelloides. MIC and MBC values of extracts were found in the range of 0.625 to 5.000 mg/ml. Extracts of honey showed good antibacterial activity against most organisms than the standard antibiotics such as Ampicillin and Gentamycin. Honey extracts showed antibacterial activity against most microorganisms which were showing some degree of resistance to commercial antibiotics. Extracts from South African honeys and medicinal plants exhibited variable activities against different microorganisms. This result suggests that the honeys could potentially be used as an alternative therapeutic agent against certain microorganisms.

Keywords: Agar well diffusion assay, honey, minimum inhibitory concentration, minimum bactericidal concentration

African Journal of Biotechnology, Vol. 13(4), pp. 616-625, 22 January, 2014