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. 2010 Jun 28;54(9):3790–3798. doi: 10.1128/AAC.01783-09

FIG. 2.

FIG. 2.

Effect of CIP and SXT on the production of Stx. The fold difference in toxin production compared to the no-antibiotic control was determined by using the luciferase assay. Each symbol represents one of three to six independent trials, and the horizontal dash denotes the geometric mean. Statistical significance (P < 0.05, Student unpaired t test with Welch's correction for unequal variance) compared to the no-antibiotic control is indicated by an asterisk. (A) Dose-response study. The O157:H7 strain PT-32 was incubated with subinhibitory concentrations of CIP or SXT. (B and C) Response of other strains to CIP (B) and SXT (C). E. coli strains inoculated in the stationary phase or the logarithmic phase were incubated overnight with CIP or SXT at 1/2 the MIC. In the absence of antibiotic, C600::933W, PT-32, and PT-40 produced between 8 and 27 μg of Stx/ml, whereas C600::H19B produced between 32 and 58 μg of Stx/ml.