Plenty of the Work I now do is associated with aseptic manufacturing. In actuality, many of the companies I work for, have products that will need to be sterile and can’t be terminally sterilized. Thus, a filtration step is required to purge the majority drug product. To build in sufficient sterility assurance from the procedure, the bioburden before filtration has to be determined. According to the notice for advice, the bioburden should be NMT 10CFU/100mL, based on the size of the filter and the volume to be filtered. Determination of the bioburden is Performed based on EP 2.6.12 or USP <61>. Both approaches are harmonized. The descriptions in the monographs state more than one way of doing this analysis, however, since the majority solution during production will be filtrated, the filtration system are the technique of choice. From the chapter at the USP and the EP, there is also mentioned that the suitability of this method ought to be evaluated and it is also mentioned how this should be accomplished.
In short, it will be examined whether the compound/solution you are likely to filter may interfere with the ability of micro-organisms to grow. Throughout the testing, the majority will be Filtered over a membrane filter and following that, the filter will be cleaned using a solvent. The USP and EP describe several solvents which may be used. So basically, the idea is that all material will be washed of the filters and the micro-organisms will remain on the filter. The filter will be incubated on two types of agar plates one for the counting of bacteria TAMC and on for the counting of fungi and yeast. After incubation, the number of colonies on the filters could be counted and this way the amount of CFU/volume tested can be set. So as to find out the suitability of the technique, bulk solution spiked with micro-organisms the kinds are described in the EP and USP will be filtered and the filters will be cleaned with solvent and the filters will be incubated. As controls, the exact steps will be achieved with solutions containing micro-organisms, but without the bulk drug product alternative.
After incubation, differences between the counts on the filters with bulk drug product and with no bulk drug product can’t differ more than a factor of two. If the gap is greater than a factor of two for any of the micro-organisms examined, the procedure isn’t right and the analytical method has to be enhanced, by either changing the washing solvent, the sort of filter or the agar where the plates are incubated. Eventually this should lead to a method for the determination of the prefiltration bioburden testing, that is acceptable for all micro-organisms mentioned in the EP or USP. If the above criteria can’t be fulfilled for one of the organisms tested with any of the described methods, the method and test conditions that come closest to the standards are utilised to check the product.