In vitro Antibacterial Activity of Selected Honey Samples on Clinical Isolates of Staphylococcus aureus Obtained from Patients' Wounds
Githinji, James Magondu
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The present study evaluated the antibacterial potency of some selected honey types in Kenya against Staphylococcus aureus. This bacterial species causes wound infections, impetigo, breast abscesses, boils, osteomyelitis and toxic shock syndrome. It is also known to cause other more serious diseases like Staphylococcal pneumonia. It can produce exotoxins that cause food poisoning as well. The aim of this study was to determine the antibacterial efficacy of some selected honey samples in Kenya using in vitro bioassay. Ninety two wound dressing swabs were collected from in-patients at Nyeri Provincial General Hospital targeting Staphylococcus aureus. Bacterial cultures were obtained. Six different types of multi floral honey were used for bioassay in this study. Three of these were refined commercial honeys while the other three were raw. Antibacterial susceptibilities were done using disk diffusion. Both Minimum Inhibition Concentrations (MICs) and Minimum bactericidal Concentrations (MBCs) were determined by serial dilution by macro dilution broth method. Contact bioautography was also done for the phytochemical chromatograms. The antibiotics used as the controls in the contact bioautography were Penicillin with a disc potency of 10 IU (455 ug) and Vancomycin 30llg. Staphylococcus aureus ATCC 25923 strain was used as the standard strain. Standard bacterial suspensions were prepared using the 0.5 McFarland's standard. Each type of honey was tested against the eighty one bacterial isolates and the data used for analysis at 0.05 level of significance. Alkaloids and flavonoids present in honey demonstrated significant (p < 0.05) antibacterial effect against Staphylococcus aureus compared to the other phytochemicals according to the in vitro tests. Both the flavonoids and alkaloids had significantly (p < 0.05) larger zones of inhibition than penicillin but significantly (p < 0.05) smaller than vancomycin disks. Hydrogen peroxide inactivated honey samples revealed significantly smaller zones of inhibition (p < 0.05) compared to the hydrogen peroxide active honey samples. Honey from Mt. Kenya forest and Kitui had the lowest MBC and MIC levels that were significantly (p < 0.05) different from those of the other honey samples in the study. The MIC and MBC in vitro potency of the two honey samples did not vary significantly (p > 0.05).The control bacterial strain was more susceptible to both the honey samples and the control antibiotics than the clinical isolates. The MIC of the honey samples ranged from' 6 - 8 % v/v on the test bacterial organisms, and MBC ranged betweenTs - 16 % v/v signifying its high potency. The results obtained in this study have confirmed that Staphylococcus aureus is a frequent clinical isolate. The in vitro bioassay results revealed that honey samples obtained from Kitui and Mt. Kenya forests had higher potency levels against the Staphylococcus aureus clinical isolates as well as the standard strain. At low dilution, commercial honeys retained a significant antibacterial potency because of the presence of hydrogen peroxide. Raw honeys are more suitable for in vivo experiments and require further molecular analysis for the purpose of safe and effective clinical application.