Evaluation of the synergistic effect of antibiotics and plant extracts or phytochemicals on resistant bacterial samples
This evaluation was done according to Muroi and Kubo (28). Aliquots of 100 µL of resistant bacterial cultures (106 cells/mL) grown in 10 mL of nutrient broth for 6 h were inoculated in nutrient broth supplemented with the respective antibiotics (50 µg/mL) with different concentrations of plant extracts. The concentration for plant extracts/phytochemicals ranged from 10 to 500 µg/mL, based on MIC values, that had previously been evaluated. Only ampicillin and/or chloramphenicol and/or tetracycline were used at the sub-inhibitory concentration (50 µg/mL). The growth conditions were the same as previously mentioned. After 48 h, the optical density of each sample was documented and compared to those of MIC to verify any synergistic effect among the tested compounds.