Jun 01, 2003 · An autoclaved MF-Millipore™ membrane filter (Millipore; diameter, 25 mm; pore size, 0.22, 0.3, or 0.45 µm) was placed and dried for 45 min on an LB agar or a blood agar plate. 10 µl of bacterial suspension (approximately 2×10 8 CFU ml −1 of saline) was spotted at the center of the filter on the agar medium without direct