Fig. 6: Association and invasion to epithelial cells, IL-8 secretion and haemolysis for MT120 and 28 (serotype 38) and MT93 and 23 (serotype 23B).

a Number of bacteria associated with epithelial cells, recovered after 3 h of incubation, b Number of intracellular bacteria after 3 h incubation and 1 h with gentamicin treatment, c IL-8 produced by epithelial cells, incubated with bacterial cells for 6 h. NI non-infected control. d haemolysis promoted by the different bacterial strains (lower OD corresponds to higher haemolysis), for different bacterial dilutions (neat~1·5 × 10⁶ bacterial cells. Results for 1/2, 1/5 and 1/10 dilutions are shown). Representative strains from each MT were used in these experiments. Each experiment was repeated at least 3 times independently. In a, b, and c, dots on the bar plots show the result of each repetition. All p-values derived using Wilcoxon ranked-sum test: a serotypes 38 and 23, p-values = 0.31 and 0.34, respectively; b serotypes 38 and 23 p-values = 1 and 0.03, respectively; c NI vs MT120, p-value = 0.032; NI vs MT28, p-value = 0.16; MT28 vs MT120, p-value = 0.42; NI vs 93, p-value = 0.1; NI vs 23, p-value = 0.016; 93 vs 23, p-value = 1; d MT120 vs MT28: neat, p-value = 0.11; 1-in-2, p-value = 0.33; 1-in-5, p-value = 0.4; 1-in-10, p-value = 0.3; MT93 vs MT23: neat, p-value = 0.03; 1-in-2, p-value = 0.33; 1-in-5, p-value = 0.2; 1-in-10, p-value = 0.3. Data are represented as mean values and error bars are the standard errors of the mean. All p-values reported are for two-sided statistical tests.