Abstract
We have previously reported on the preliminary characterization of Hydrogenophaga (formerly Pseudomonas) pseudoflava for potential use as a standard challenge organism to qualify 0.1 μm rated filters. This article reports on the retention efficiencies of a large panel of 0.2/0.22 μm and 0.1 μm rated filter cartridges for H. pseudoflava (ATCC 700892) versus the retention capabilities of the same filters for Brevundimonas diminuta (ATCC 19146). A total of thirty-two 0.2/0.22 μm rated filter cartridges, spanning nine different “sterilizing grade” filter types from four different filter manufacturers, were challenged with H. pseudoflava at challenge levels exceeding 107 cfu/cm2. H. pseudoflava was shown to penetrate every 0.2/0.22 mm rated filter tested, with log titer reduction (LTR) values ranging from 3.5 to 7.7 logs. H. pseudoflava was shown to be more penetrative than B. diminuta under the same challenge conditions. B. diminuta was fully retained by nineteen of the twenty 0.2/0.22 μm rated filters that were challenged with both organisms. In the case of 0.1 μm rated filters, eighteen filter cartridges, spanning five different filter types from three manufacturers were tested. H. pseudoflava was consistently retained by four out of the five filter types tested, with LTR values in excess of 11.5 to 12.2 logs. The 0.1 μm rated filter type that was penetrated by H. pseudoflava has been previously demonstrated to be not fully retentive for naturally occurring bacteria. The data show that H. pseudoflava penetrates 0.2/0.22 mm rated filters just as readily as B. diminuta penetrates 0.45 μm rated filters. In addition, titer reductions provided by 0.2/0.22 rated filters for H. pseudoflava are comparable to those reported for A. laidlawii mycoplasma, albeit under different conditions. This study demonstrates that H. pseudoflava meets all criteria for use as a standard organism for qualifying the microbial removal performance of 0.1 μm rated filters for enhanced sterility assurance.
Footnotes
↵1Current affiliation: Immuno-Rx, New York
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- The Importance of Accurate Microorganism Identification in Microbial Challenge Tests of Membrane Filters. Part II. The Comparison of Hydrogenophaga pseudoflava ATTC 33668 and Curvibacter sp. ATCC 700892 by Microbial Challenge Tests with Membrane Filters
- The Importance of Accurate Microorganism Identification in Microbial Challenge Tests of Membrane Filters--Part I
- Use of Hydrogenophaga pseudoflava Penetration To Quantitatively Assess the Impact of Filtration Parameters for 0.2-Micrometer-Pore-Size Filters
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