FIG 6.
ADO sensitizes S. aureus to antibiotic killing. (A) S. aureus intracellular nucleotide concentrations 15 min after downshift from LB broth into M9 minimal medium. Selected samples were treated with vehicle or 1 mM ADO. (B to G) To establish MDK values, antibiotic killing was determined in S. aureus cultures after downshifting from exponential-phase LB broth to M9 medium supplemented with 0.2% Casamino Acids, 5 μg/mL thiamine, and 2 μg/mL nicotinic acid, without glucose. Selected samples were treated with vehicle or 1 mM ADO in the presence of 15 μg/mL GEN, 100 μg/mL AMP, 15 μg/mL CRN, 5 μg/mL VAN, 500 ng/mL CIP, or antibiotic vehicle control. Data are the mean of three biological replicates ± SEM. *, P < 0.05; **, P < 0.01; ***, P < 0.001, as assessed by Student's t test. Dotted line indicates MDK99.99 threshold. Asterisk denotes significant difference between treatment groups. ABX, antibiotics; ADO, adenosine; AMP, ampicillin; CIP, ciprofloxacin; CRN, ceftriaxone; GEN, gentamicin; VAN, vancomycin; VEH, vehicle control.