Microbial retention characteristics of 0.2-microns-rated nylon membrane filters during filtration of high viscosity fluids at high differential pressure and varied temperatures.

Regulatory guidelines for aseptic manufacture of pharmaceuticals recommend validation of sterilizing filters by bacterial challenge under "worst case" conditions. The microbial retention characteristics of a sterilizing grade, 0.2-microns-rated Nylon 66 membrane filter were evaluated for filtration of high viscosity fluids. Glycerol (80%) was used as the carrier fluid and Pseudomonas diminuta ATCC 19146 as the challenge organism. Testing was carried out at a constant differential pressure of 60 psig over a six-hour test period. Test runs were undertaken at three different temperature conditions (25 +/- 5 degrees C, 42 +/- 1 degree C, and 50 +/- 1 degree C). Under the test conditions, the Nylon 66 membranes provided total retention of P. diminuta. The results demonstrated that a high pressure differential challenge using a high viscosity fluid over a six-hour test period at ambient and elevated temperatures did not alter the retention characteristics of the membrane filter.