Effects of food spices on Gram-negative food indicator bacteria from some Nigerian ethnic fermented plant food condiments

Abstract

Varied but multiple antibiotic resistance rates were exhibited by all the foodborne indicator bacterial species, Citrobacter, Escherichia coli, Enterobacter, Klebsiella,Morganella morganii, Salmonella, Shigella, Pseudomonas isolated from four most-popular Nigerian indigenous fermented plant food condiments ogiri, iru, okpehe andugba. The generally most-resisted antibiotics (discs) were tetracycline (44.0 - 63.0%), cotrimoxazole (56.0 - 70.3%), nalidixic acid (28.0 - 74.1%), amoxicillin (28.0 - 88.9%) and augmentin (16.0 - 94.4%), while the least resisted antibiotics were ofloxacillin (0.0% - 1.85%) and gentamicin (4.0 - 16.7%). Antibacterial activities of crude extracts of local spices and essential oils of plant origin, as well as carvone, lactic and acetic acids on the multiple antibiotic resistant Gram-negative foodborne bacterial species were determined using modified agar well-diffusion assay. Crude extracts of Eugeniaaromatica (92.0%) and Allium sativum (72.0%) were maximally inhibitory; lactic (44.4%) and acetic (46.3%) acids were moderately inhibitory but essential oils of Eugeniauniflora (24.0%), Ageratum conyzoides (16.7%) and Chrsophylum albidium juice (13.0%) were minimally inhibitory in vitro, indicating that crude extracts of E. aromaticaand A. sativum can serve as easily prepared, non-chemical, plant-based, adjunct preservatives of fermented condiments both domestically and industrially, even by the traditional producers of the indigenous and similar condiments. Key words: Cottage food production, essential oils, food safety, food processing, multiple antibiotic resistance, Nigerian indigenous fermented foods, plant foods.