Statistically significant decreases in bacterial loads are indica

Statistically significant decreases in bacterial loads are indicated with asterisks (*, P<0.05; * *, P<0.01). Compared to the single-strain challenge model, the competitive co-infection model using both parent strain and its isogenic mutant can demonstrate more sensitivity to differences in colonization or virulence. In co-infection experiments, both E058ΔchuT and E058ΔiucD did not demonstrate any significant decrease in pathogenicity compared to E058 wild-type in organs (Figure 2) (P>0.05), while E058ΔiroD was highly attenuated and showed a significantly

reduced competitive index (CI), with Selleckchem Vactosertib mean decreases of 77–fold, 70-fold, and 37–fold compared to E058 in liver (Figure 2b), lung (Figure 2d) and kidney (Figure 2e) (P<0.01), respectively. For U17 and its isogenic mutants, U17ΔchuT demonstrated no significant PHA-848125 in vitro decreases compared to U17 in all internal organs tested (Figure 2) (P>0.05), while U17ΔiroD CFU counts were highly reduced, with mean decreases of 105-fold, 49-fold, 80-fold, and 46-fold compared to the wild-type strain in liver (Figure 2b), spleen (Figure 2c), lung (Figure 2d), and kidney (Figure 2e) (P<0.01), respectively. U17ΔiucD showed significantly reduced CI in the heart, with a mean 4.2-fold decrease compared to U17 (Figure 2a) (P<0.05), but

demonstrated no significant differences in all the other organs (P>0.05). In co-infection assays using the triple mutants, the ΔchuTΔiroDΔiucD mutants in E058 and U17 were both significantly more attenuated than each of the single mutants, with average decreases of 147-fold and 196-fold in organs tested (Figure 2) (P<0.01), respectively. Figure 2 Competitive

co-infection model was used in which E058 or U17 and isogenic mutants were inoculated simultaneously. At 24 h post-infection, tissues were sampled, and results are presented as the log10 competitive index (CI). The CI represents the relative Rapamycin in vitro numbers of the two test strains from the tissues sampled (the output ratio) compared to the OICR-9429 molecular weight initial numbers of the strains in the inoculum (input ratio). Negative CI values indicate a decreased capacity for the mutant to compete with the virulent wild-type strain. Horizontal bars indicate the mean log10 CI values. Organs sampled were the heart (a), liver (b), spleen (c), lung (d), and kidney (e). Statistically significant decreases in CI values are indicated with asterisks (*, p<0.05; **, p<0.01). Bactericidal effect of specific-pathogen-free (SPF) chicken serum on E058 and U17 and isogenic mutants The ability of the isogenic mutants defective in iron acquisition systems to survive in SPF chicken serum was not affected, as tested by bactericidal assay, indicating that the iron acquisition systems may be unrelated to serum complement resistance. Growth of iron acquisition mutants in iron-rich and iron-restricted medium All mutants were grown in LB with or without 200 μM 2,2′-dipyridyl (DIP).

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