Staphylococcus aureus ATCC 6538 as a Gram-positive bacterium and Escherichia coli ATCC 8739 as a Gramnegative bacterium were used in this study.
The test strains were maintained as frozen stocks at 70C in PBS (phosphate buffered saline) containing 20% (v/v)glycerol.
Fresh cultures were prepared by inoculating 100 ml aliquots of the thawed microbial stock suspensions into CASO agar plates followed by overnight incubation at 35C. The bacteria inocula were prepared by suspending overnight colonies from CASO agar medium in 0.9% saline. The
inocula were adjusted photometrically at 600 nm to a cell density equivalent to 0.5 McFarland standard (1.5x108 CFU/ml) before use.