Fig. 6

Role of type 2b pili in GBS ST-17 COH1 host cell adherence and invasion. a Adherence and b invasion assays were performed in hBMEC and A549 cells with COH1 WT and isogenic mutants. Mid-log phase bacteria were added to confluent cell monolayers at a multiplicity of infection of 1. Total cell-associated GBS bacteria were recovered after 30 min, and intracellular bacteria were recovered after 2-h infection plus 2-h incubation with antibiotics as described in Materials and Methods. GBS was quantified by serial dilution plating to enumerate CFU and expressed as (recovered CFU/initial inoculum CFU) ×100%. All adherence and invasion assays were performed in triplicate and repeated at least three times. Each bar represents means and standard deviation of three independent experiments, each performed in triplicate. Differences between groups were analyzed by One-Way ANOVA followed by Tukey’s multiple comparisons test. Only statistically significant differences are reported (* P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001)