Susceptibility of bacterial and fungal isolates to spices commonly used in Ghana

Abstract

Spices are used as flavoring agents, preservatives and colorants; also in medicine, religion, tradition and magic in parts of the world. This work was designed to test the susceptibility of the clinical isolates - Salmonella sp., Klebsiella sp., Staphylococcus aureus (S. aureus), Escherichia. coli (E. coli) and Candida albicans to the single spices and their combinations. Twenty single spices and their combinations were extracted with ethanol, and zones of inhibition (ZOI), minimum inhibitory concentrations (MIC) and minimum bactericidal/fungicidal concentrations (MBC/MFC) determined by Agar Well Diffusion and Dilution Tube Methods respectively. The microbes showed various susceptibilities to the spices compared to the controls, all at a concentration of 100 µg/ml, with the highest effect by the spice combinations. All the five isolates showed the highest susceptibility towards Cloves and Negro pepper together followed by Guinea and Ashanti peppers, then Rosemary and Aniseed. Even though all the single spices were effective against Klebsiella sp., none of them showed susceptibility towards E. coli. The MIC for the combined spices was dominant at 125 µg/ml, whiles MIC for the single spices ranged between 250 and 1000 µg/ml. Analysis of variance (P<0.05) between the single spices and their combinations recorded 0.4587, 0.0094 and 0.0012 for ZOI, MIC and MBC/MFC respectively. The resulting susceptibilities of the microbes to the combined spices over their single counterparts suggest a better synergy and food hygiene effect when their right selection, pairing and quantities are determined, and could be useful for the development of antimicrobial products against persistent human infections.