Figure 2 | npj Microgravity

Figure 2

From: Physiological fluid shear alters the virulence potential of invasive multidrug-resistant non-typhoidal Salmonella Typhimurium D23580

Figure 2

Resistance of Rotating Wall Vessel (RWV)-cultured D23580 to pathogenesis-related stresses. Bacterial cultures were grown in the RWV under low fluid shear (LFS; white bars) or higher fluid shear (HFS; gray bars), removed from reactors, and immediately subjected to the stress indicated. All tests were performed using a minimum of two independent biological replicates. (a) Bile stress was induced by the addition of a bile salt solution (Sigma-Aldrich, St. Louis, MO, B8756) to a final concentration of 10% in each culture. The results from a representative experiment are shown. (b) Oxidative stress was induced by adding hydrogen peroxide (H2O2) to a final concentration of 0.06% in the culture. Combined results from all trials are shown. (c) Acidic conditions were induced through the addition of a small pre-determined volume of citrate buffer (stock concentration of 1 m citrate, 0.513 m sodium phosphate dibasic heptahydrate) to lower the pH to 3.5. Combined results from all trials are shown. The pH was confirmed at the end of all experiments. For all stresses, samples were serially diluted in phosphate-buffered saline (PBS) and plated on Lennox Broth (LB) agar at time zero (T0, before the addition of stress) and at the indicated time points thereafter to determine the numbers of viable colony-forming units (CFU). Data were normalized at each time point to the number of initial bacteria subjected to the stress. The data are presented as the mean percent survival values with error bars indicating the Standard error of the mean. Statistical comparisons were made using Student’s t-test (***P<0.001; **P<0.01).

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