Tobramycin base

Vibrio harveyi BB170 (ATCC BAA-1117), S. aureus ATCC 25923, P. aeruginosa PAO1, and E. coli OP50 were used in this study. AB medium contained 0.3 M NaCl, 0.05 M MgSO₄, and 2% acid-hydrolyzed casein (without vitamins), adjusted to pH 7.5 with 1 M KOH. After autoclaving at 121°C, 10 ml of 1 M potassium phosphate buffer (K₂HPO₄/KH₂PO₄, pH 7.0), 10 ml of 0.1 M sterile arginine solution (L-Arg), and 20 ml of 50% sterile glycerol were added to the medium (per 1 L). LB medium contained 1% tryptone, 1% NaCl, and 0.5% yeast extract. TSB medium contained 1.5% tryptone, 0.5% soy peptone, and 0.5% NaCl (pH = 7.2 ± 0.2). PB medium contained 2% peptone, 1% K₂SO₄, and 0.3% MgCl₂. PTSB medium contained 5% peptone, 1.7% tryptone, 0.5% NaCl, 0.25% K₂HPO₄, 0.25% glucose, and 0.3% soy peptone. PGS-agar plates contained 1% peptone, 0.15 M sorbitol, 1% NaCl, 1% glucose, and 1.7% agar. Swimming solid medium contained 0.8% nutrient broth, 0.5% glucose, and 0.3% agar. Swarming solid medium contained 0.8% nutrient broth, 0.5% glucose, and 0.5% agar.
Test compounds were dissolved in DMSO to a stock concentration of 65 mM. Antibiotics [tobramycin base, meropenem trihydrate (MEPM), ceftazidime, amikacin, colistin sulfate, and ciprofloxacin] were purchased from Sigma and stored at 6.4 mg/ml at −20°C.

C. violaceum CV026, E. coli OP50, and P. aeruginosa PAO1, representing wildtype strains, were stored in our laboratory. Luria–Bertani (LB) broth (1% tryptone, 1% NaCl, 0.5% yeast extract) was typically used to cultivate the bacteria, in which C. violaceum CV026 was cultivated at 30 °C; P. aeruginosa PAO1 and E. coli OP50 were cultured at 37 °C. Dimethyl sulfoxide (DMSO) was used to dissolve the test compound to a stock concentration of 65 mM. The tobramycin base was purchased from Sigma (St. Louis, MO, USA), and it was stored at 6.4 mg/mL.

Hydrogen tetrachloroaurate(III) hydrate ( $HAuC{l}_4.3H_{2}O$ , M.W: 339.79 $g.mol{e}^{-1}$ , $\backsim$ 52% Au basis, anhydrous basis) purchased from sigma aldrich, Egypt. Trisodium citrate dihydrate ( $N{a}_3{C}_6{H}_5{O}_7.2H_{2}O$ , M.W.: 294.10 $g.mol{e}^{-1}$ , $>99.0$ %) purchased from Gateway Co. Double Distilled Water freshly obtained from Automatic Water Still, for all preparations, and rinsing thoroughly all glasswares. Alendronate sodium ( $C_4{H}_{12}NNa{O}_7{P}_2$ , M.W: 271.08 $gmol{e}^{-1}$ ), memantine ( $C_{12}{H}_{21}N$ , M.W: 179.30 $gmol{e}^{-1}$ ) and Tobramycin base ( $C_{18}{H}_{37}{N}_5{O}_9$ , M.W: 467.45 $gmol{e}^{-1}$ ) purchased from sigma aldrich, Egypt. Aqua Regia (1:3 mixture of concentrated concentrated nitric acid ( $HN{O}_3$ ) to concentrated hydrochloric acid (HCl)) used continuously to wash out all glasswares before and after each procedure.