Abstract: Many of the spices used daily in our homes have been documented to be antimicrobial and have medicinal value as well. Spices such as garlic and ginger have been used as antimicrobial agents in their raw form for the treatment of wounds, injuries and joint pains. The present study investigated the antimicrobial activity of heated extracts (ethanolic and aqueous) of garlic (Allium sativum) and ginger (Zingiber officinale) on some selected pathogens using the agar-well diffusion assay method. Three different concentrations of the extracts (i.e. 2.5 mg/ml, 5.0 mg/ml and 10.0 mg/ml) were prepared and used for the study. The antimicrobial activity of these heated extracts was tested against Staphylococcus aureus, Salmonella typhi, Klebsiella pneumoniae, Escherichia coli, Candida albican, and Proteus mirabilis at different concentrations of the extracts. The results showed that neither the heated ethanolic extracts nor the heated aqueous extracts of A. sativum had antimicrobial activity against any of the test organisms. Similarly, heated aqueous extracts of Z. officinale showed no activity against any of the test organisms. Only the heated ethanolic extracts of Z. officinale showed some level of activity against C. albicans (8.5 -11.0 mm) and S. typhi (7.0 -14.5 mm). The findings of the study were attributed to the high temperatures used during the extraction phase, which may have caused the denaturing of some bioactive compounds resulting in the ineffectiveness of the extracts against the test microorganisms. It is therefore suggested that, garlic and ginger should not be heated or cooked if they are to be used for medicinal purposes
