Minimum inhibitory concentration (MIC)

MICs were determined using the broth microdilution method according to the guidelines of the Clinical and Laboratory Standards Institute (15). Briefly, a microorganism suspension was prepared by growing bacteria in broth for 24 h, and adjusting to a 0.5 McFarland standard turbidity (~1.5×10⁸ CFU/ml). Final inoculums were adjusted to 1.5×10⁶ CFU/ml. Serially diluted antibiotics and/or LUT were then incubated with the inoculum at 37°C for 18 h. The MIC was the lowest effective concentration of antimicrobial agent. At the end of the incubation period, the wells were visually examined for turbidity. Cloudiness indicated that bacterial growth had not been inhibited at the concentration of antimicrobial agent in the medium.