1. Day 1: Grow bacteria overnight in 10 ml 3% TH medium at 37 °C, 200 rpm. 2. Day 2: Subculture 100 μl of overnight bacteria in 10 ml fresh 3% TH medium to mid-exponential phase (OD620 ~ 0.5), 37 °C, 200 rpm. 3. Centrifuge bacteria (10 min, 5,000 rpm), remove supernatant, wash pellet twice with 10 ml 50 mM Tris/HCl (pH 7.4). 4. Resuspend pellet in 50 mM Tris/HCl (pH 7.4) + 50 µM ZnCl2 to 2 x 10^9 cfu/ml. 5. Incubate 100 µl bacteria with 10 µl test agent or buffer (positive control) for 60 sec at RT. 6. Add 100 µl citrate plasma, incubate 35 min at 37 °C, 200 rpm. 7. Spin down bacteria (6 min, 5,000 rpm), wash pellets once with 50 mM Tris/HCl (pH 7.4). 8. Resuspend in 100 µl 50 mM Tris/HCl (pH 7.4) + 50 µM ZnCl2 + 2 mM chromogenic substrate S-2302. 9. Incubate 30-60 min at 37 °C, centrifuge (6 min, 5,000 rpm), transfer supernatants to 96 well plate. 10. Measure absorbance at 405 nm. For assay without bacteria, follow similar steps with modifications as specified.