Susceptibility of isogenic morphotypes to selleckchem reactive oxygen intermediates (ROI) The susceptibility of 3 morphotypes to ROI was
initially examined on LB agar plates containing a range of H2O2 concentrations (0, 170, 310, 625, 1,250 and 2,500 μM) (data not shown). B. pseudomallei failed to grow on plates with H2O2 at a concentration higher than 625 μM, and so the percentage of viable bacteria were enumerated using agar plates with 625 μM H2O2 compared to those on plates without H2O2. This demonstrated a difference in bacterial survival between the three isogenic morphotypes (P < 0.001). Percentage survival of type I was 3.8 (95%CI 2.9-5.0, P < 0.001) times higher than that for type II, and was 5.2 (95%CI 4.0-6.8, P < 0.001) times higher than that for type III (Figure 2A). Figure 2 Susceptibility of 3 isogenic morphotypes
of B. pseudomallei to ROI and antimicrobial peptide LL-37. Survival was examined for 5 different B. pseudomallei isolates. (A) Percent survival in ROI was determined AZD9291 mw on LB agar plates containing 625 μM H2O2 compared to the number of bacteria on plates without H2O2. The results were obtained from 4 separate experiments. (B) Percent survival in LL-37 was determined at 6.25 μM LL-37 in 1 mM potassium phosphate buffer (PPB) pH 7.4 for 6 h. The results were obtained from 2 separated experiments. Data plots are means ± standard deviations. Further examination was undertaken of the susceptibility of the 3 morphotypes with a range of concentrations of H2O2 in LB broth. No bacteria survived in 500 μM and 250 μM H2O2. In 125 μM H2O2, type I of all 5 isolates multiplied from 1 × 106 CFU/ml (the starting inoculum) to between 5 × 107 and 2.1 × 108 CFU/ml. By contrast, all 5 type III and 4 type II isolates (the exception being type II derived from isolate 164) obtained from the same MLN2238 mouse experiment PLEK2 demonstrated no growth on the plates. This confirmed a higher resistance to H2O2 of parental type I compared to types II and III. A difference was also observed between three isogenic morphotypes in 62.5 μM H2O2 (P < 0.001). Bacterial growth of type I was 1.5 (95%CI
1.1-2.0, P = 0.02) times higher than that for type II, and was 2.7 (95%CI 2.0-3.7, P < 0.001) times higher than that for type III. Susceptibility of isogenic morphotypes to reactive nitrogen intermediates (RNI) Susceptibility of B. pseudomallei to RNI was observed following 6 h exposure to various concentrations of NaNO2 ranging between 0.1 to 10 mM in acidified pH 5.0 in LB broth. Using a concentration of 2 mM NaNO2, the percent survival of types I, II and III were 43.8%, 43.7% and 40.1%, respectively, with no difference observed between the three morphotypes (P > 0.10). Susceptibility of isogenic morphotypes to lysozyme and lactoferrin Compared with initial inocula and untreated controls, treatment with 200 μg/ml lysozyme at pH 5.0 did not decrease the bacterial count for the 3 isogenic morphotypes of B.