TABLE I

Results of B. diminuta Bacterial Challenge Tests of Various Commercially Available 0.2 μm Rated Sterilizing-Grade Filters and One 0.1 μm Rated Sterilizing-Grade Filter Using a Liposome Solution as the Challenge Solution

Filter and Rating (μm)		Integrity Test (Bubble Point; psi)		Flux (mL/min/ cm²)	Challenge Differential Pressure psid (mbar)	Total Challenge (CFU)	Challenge (CFU/cm²)	Penetration (Total CFU)	Titer Reduction
Filter and Rating (μm)		Pre-challenge	Post-challenge	Flux (mL/min/ cm²)	Challenge Differential Pressure psid (mbar)	Total Challenge (CFU)	Challenge (CFU/cm²)	Penetration (Total CFU)	Titer Reduction
A1	0.2	68.0	62.0	0.4	37 (2549)	3.4 × 10⁸	1.9 × 10⁷	>200	BML^*
A2	0.2	68.4	62.8	0.3	40 (2756)			69	4.9 × 10⁶
A3	0.2	70.0	61.6	0.3	40 (2756)			>200	BML
Average A				0.3	39 (2687)
B1	0.2	52.4	49.6	0.6	32 (2205)	4.2 × 10⁸	2.4 × 10⁷	44	9.5 × 10⁶
B2	0.2	52.0	47.2	0.4	30 (2067)			68	6.2 × 10⁶
B3	0.2	56.0	48.0	0.3	29 (1998)			4	1.1 × 10⁸
Average B				0.4	30 (2067)
C1	0.2	62.0	50.0	0.6	36 (2480)	2.2 × 10⁸	1.4 × 10⁷	>200	BML
C2	0.2	60.8	50.0	0.5	35 (2412)			>200	BML
C3	0.2	62.0	54.0	0.3	37 (2549)			>200	BML
Average C				0.4	36 (2480)
D1	0.2	59.2	54.0	0.9	41 (2825)	3.9 × 10⁸	2.8 × 10⁷	>200	BML
D2	0.2	58.0	52.4	0.6	37 (2549)			>200	BML
D3	0.2	56.8	51.6	0.8	40 (2756)			>200	BML
Average D				0.8	39 (2687)
E1^**	0.2	52.0	49.2	0.4	42 (2894)	2.3 × 10⁸	1.7 × 10⁷	>200	BML
E2	0.2	54.4	50.8	0.7	44 (3032)			>200	BML
E3	0.2	51.2	50.0	0.7	43 (2963)			>200	BML
Average E				0.6	43 (2963)
F1^**	0.2	66.0	63.2	0.30	47 (3238)	3.7 × 10⁸	2.7 × 10⁷	0	>3.7 × 10⁸
F2	0.2	65.2	62.0	0.17	47 (3238)			18	2.1 × 10⁷
F3	0.2	55.6	59.2	0.25	48 (3307)			0	>3.7 × 10⁸
F4	0.2	65.6	66.4	0.15	42 (2894)	5.0 × 10⁸	3.6 × 10⁷	0	>5.0 × 10⁸
F5	0.2	56.2	64.0	0.14	49 (3376)			21	2.4 × 10⁷
F6	0.2	55.6	60.0	0.14	44 (3032)			8	6.3 × 10⁷
Average F				0.19	46 (3169)
G1^**	0.1	35.2	37.2	0.19	46 (3169)	2.7 × 10⁸	2.0 × 10⁷	0	>2.7 × 10⁸
G2	0.1	34.8	36.8	0.16	45 (3101)			0	>2.7 × 10⁸
G3	0.1	30.0	36.0	0.17	45 (3101)			0	>2.7 × 10⁸
Average G				0.18	45 (3101)

The average flux over the course of the challenge, for each filter, is given in the third column, and the average of the individual filter flux values is shown below that. The differential pressure at which the challenge was run is given in a similar manner. All the bubble points were determined with water-wet filters, with the exception of Filter G, in which case 60% isopropyl alcohol was used as the wetting fluid.
↵* BML = below measurable limit. Titer reduction was below the measurable limit of this test system, indicated by more than 200 CFU found on the recovery discs, which placed them outside the countable limits. Where more than 200 cells were found, then the value was simply noted as >200, and it was not possible to determine the titer reduction because it was not possible to determine the number of cells that passed the filter.
↵** Pall Corporation filters (E, F, and G); the others were commercially available 0.2 μm rated sterilizing-grade filters from four other major filter vendors.