Figure 2.

Example of SGT method use: assessment of the relative bactericidal activity of meropenem on various P. aeruginosa isogenic mutants. (A) Wild-type PA14 (blue) and its isogenic mutant derivatives mvfR (black) and pqsBC (red) were grown to mid-logarithmic phase before being subjected to a 24 h treatment with meropenem (10 mg/L) at 37°C (no meropenem added to normalizers). Following 1:500 dilution, the growth kinetics of normalizers and treated samples were recorded. Employing an OD_600nm = 0.15, ∆SGT values were calculated as the difference between treated and normalizer SGTs. ∆∆SGT values were calculated as the difference of between ∆SGTs of the mutants to that of wild-type PA14, which served as the calibrator. (B) For the SGT method, log₂ fold of change was calculated as -∆∆SGT (empty bars). For CFU counting, normalizers and treated cells were serially diluted and plated. For comparison purposes, CFU count results are also presented as log₂ fold of change (filled bars). The differences between the values obtained by the two methods did not differ significantly (p > 0.1).