Abstract

Herbs and spices improve the taste of food and also have medicinal properties. This study determined the antimicrobial activity of selected spices against Bacillus cereus at different pH. The active ingredients of five herbs and spices; ginger (Zingiber officinale), garlic (Allium sativa), turmeric (Curcuma longa), thyme (Thymus vulgaris) and bay leaf (Laurus nobilis) were extracted with sterile water and ethanol; and reconstituted into different concentrations. The spice extracts were tested against thirty (30) Bacillus cereus isolates recovered from food using the Agar well diffusion method. Clindamycin (2 μg) was used as standard antibiotic. The ethanol extracts of the spices were more active than the aqueous extracts. Thyme extract showed the highest activity at 100 % concentration with mean zone of inhibition of 14mm followed by bay leaf with 12 mm. Thyme and turmeric had the highest activity at pH 6 with 11 mm as the mean zone of inhibition. Ginger and garlic were more active at pH 3, thyme and turmeric at pH 7 while bay leaf was at pH 8. Only five isolates were resistant to the antibiotics. Therefore, the active ingredients of spices can be extracted, concentrated, purified and used in the treatment of infections by these pathogens and preservation of foods since most of them are now resistant to common antibiotics.