Figure 7. The susceptibility of Y. enterocolitica O:9 strains with and without protein OmpX to normal human serum.

Strains Ye9 (wt) and Ye13 (Ye9 OmpX⁻) were grown to exponential phase at 37°C and incubated with 50% NHS at 37°C. Aliquots removed at 0, 15, 30 and 60 min were plated for viability counts (CFU). The numbers of CFU/ml were normalized to the T₀ values as a percentage and then converted to log₁₀ to show the survival rate of the bacteria in NHS. Data are the means ±SD from three independent experiments. The survival of both strains decreased in NHS during incubation and the differences between strains were not statistically significant (one way ANOVA with Tukey's comparison post-test).