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 OD600nm = 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).
Hazan et al. BMC Microbiology 2012 12:259 doi:10.1186/1471-2180-12-259