2. Materials and Methods2.1. Plant MaterialThe ground seed powder of Garcinia kola was obtained from the plant www.selleckchem.com/products/epz-5676.html material collection of the Applied and Environmental Microbiology Research Group (AEMREG) laboratory, University of Fort Hare Alice. South Africa.2.2. Preparation of ExtractsThe extracts were prepared following the descriptions of Basri and Fan [19]. A 100-gram measurement of the seed powder was steeped in 500mL of methanol solvent for a 48h period with shaking in an orbital shaker (Stuart Scientific Orbital Shaker, UK). The resultant extract was centrifuged at 3000rpm for 5min at 4��C (Beckman Model TJ-6RS Centrifuge, Great Britain), the supernatant was then filtered through Whatman No.1 filter paper, while the residue was then used in the second extraction process involving 300mL of the solvent.

The combined extracts were concentrated using a rotary evaporator at 65��C (Steroglass S.R.L, Italy), after which they were dried to a constant weight under a stream of air in a fume cupboard at room temperature. Dimethyl sulphoxide (DMSO) at a concentration equal to 5% of the total volume which was made up with sterile distilled water was used to aid the reconstitution of the dried extract when making test concentrations.2.3. Test Listeria StrainsThe 42 test Listeria isolates used in this study were obtained from the culture collection of the Applied and Environmental Microbiology Research Group (AEMREG) laboratory at the University of Fort Hare, Alice, South Africa. The bacteria were previously isolated from wastewater effluents in the Eastern Cape Province of South Africa and belonged to three species groups which are L.

ivanovii, L. grayi, and L. monocytogenes [20].2.4. Preparation of the Inoculum The EUCAST [21] colony suspension method was used to prepare the inoculums of the test organisms. In brief, colonies picked from 24h old cultures were suspended in saline solution (0.85% NaCl) to give an optical density of approximately 0.1 at 600nm after which the suspension was then diluted a hundredfold before use.2.5. Antibacterial Susceptibility TestThe agar well diffusion method according to Irobi et al. [22] with modifications was used to determine the sensitivity of the test Listeria to the extract. The prepared bacterial suspension (100��L) was inoculated into sterile molten Mueller-Hinton agar medium at 50��C in a MacCarthney bottle, mixed gently, and then poured into a sterile petri dish and allowed to solidify. A sterile 6mm diameter cork borer was used to Carfilzomib bore wells into the agar medium after which the wells were filled up with approximately 100��L of 10mg/mL extract solution.