Method Essay Example | Topics and Well Written Essays - 2000 words

Method - Essay Example The antioxidants stock solutions were prepared separately. Four hundred milligrams of L-ascorbic acid and tannic acid were dissolved in 5 mL of water to make a stock solution of 80 mg/mL. Forty milligrams of epigallocatechin were dissolved in 5 mL water for a concentration of stock solution of 8 mg/mL. Cells of Staphylococcus aureus strains SH1000 and UAMS-1 were streaked on Mueller-Hinton Agar (MHA) plates and incubated 37Â °C for 24 hours. After this period, single colonies were picked, and transferred to tubes with Mueller-Hinton Broth (MHB). The tubes were placed in an incubator-shaker at 37 Â °C for another 24 hours. The overnight cultures in MHB, after appropriate dilution, served as the inocula for the experimental determination of minimum inhibitory concentration (MIC) of antibiotics and antioxidants, and mutational frequencies (MF). Overnight cultures were always used fresh, and not after storage. The desired antibiotic starting concentrations were obtained by diluting the desired volume from the stock solutions. For the determination of the mupirocin MIC, the starting concentration was 16 Â µg/mL. This amount was diluted doubly using sterile saline to produce decreasing concentrations of 16, 8, 4, 2, 1, 0.5, 0.25, 0.125, 0.0625, and 0.03125 Â µg/mL. The starting concentration of rifampicin was 2 Â µg/mL. Again, double dilution was performed. The following concentrations were used to determine the rifampicin MIC: 2, 1, 0.5, 0.25, 0.125, 0.0625, 0.03125, 0.01563, 0.0078, and 0.0039 Â µg/mL. To determine the MICs of the antioxidants that were to be used in the experiment, the antioxidants solutions were also serially diluted similar to what was done for the antimicrobials mupirocin and rifampicin. The starting concentration of all the antioxidants was 8 mg/mL. After double dilutions, the concentrations used were 8, 4, 2, 1, 0.5, 0.25, 0.125, 0.0625, 0.03125, and 0.01563 mg/mL. Cellulose ester disks with 0.22 Â µm