Fig. 7.

Interference of the GBS pigment with the coagulation system. The indicated concentrations of the pigment were incubated in human plasma for 30 min at 37°C and removed via centrifugation. aPTT (a) and PT (b) of the resulting supernatants were determined in a coagulometer. Plasma incubated with the same amount of elution buffer of the pigment served as a control. Each symbol represents one independent experiment. Bars denote median values and range from 3 independent experiments (n = 3). The level of significance was determined using Welch's t test (** p < 0.01). c Plasma clotting after incubation with the indicated dilutions of the GBS pigment. Elution buffer of the pigment served as a control. After incubation for 1 h at 37°C, the recalcification clotting times were measured. Each symbol represents one independent experiment. Bars denote median values and range from 3 independent experiments (n = 3). The level of significance between the controls and pigment samples was determined using Welch's t test (** p < 0.01, *** p < 0.001, **** p < 0.0001). d Activation of FXII/PK GBS pigment. Pigment or elution buffer (ctrl. buffer) were incubated in normal human plasma and washed, and chromogenic substrate S-2303 was added to the reaction. The FXII/PK activity was determined by measuring the absorbance (A) at 405 nm. Data represent mean values and range from 3 independent experiments (n = 3). Statistical significance between the controls and pigment was calculated using Welch's t test (* p < 0.05, *** p < 0.001). aPTT, activated partial thromboplastin time; FXII, factor XII; GBS, group B streptococcus; PT, prothrombin time.