Figure 2: Cleavage of the plasmin-specific chromogenic substrate by plasmin-bound leptospires. Live low-passage virulent and high-passage nonvirulent L. interrogans serovar Copenhageni cells received the following treatments: PBS only (PBS), uPA alone (uPA), 5 μg PLG alone (PLG), PLG in crescent quantities (0.5, 2 and 5 μg) together with uPA, and 30% human plasma together with uPA (30% plasma). Bars represent mean absorbance as a measure of relative substrate degradation ± the standard deviation of three replicates for each experimental group and are representative of three independent experiments. *Virulent leptospires experiments: statistically significant (P < 0.0001) in comparison to the PBS control; **nonvirulent leptospires experiments: statistically significant (P < 0.01) in comparison to the PBS control. The 30% plasma, as PLG source, and all the PLG + uPA samples of the virulent leptospires were statistically significant (P < 0.001) in comparison to the same nonvirulent bacteria tested samples.