Why we use 0.45 micron pore size filter in Sterility testing but 0.22 micron pore size filter during filtration?

There are different grade and pore size filters are available in the market. But for sterility testing only 0.45 micron pore size filter is recommended in different pharmacopoeias. First question comes in mind that many bacteria are present in the environment which are smaller than 0.45 micron pore size like Brevundimonas diminuta then why don't we use 0.22 micron pore size filter which can retain these small size bacteria instead of 0.45 micron? Can bacteria smaller than 0.45 micron size pass through the filter paper of 0.45 micron if yes then why we are using 0.45 pore size? Can't we use 0.22 micron pore size filter for sterility testing? There are different questions comes in mind and create confusion.

When we perform sterility testing we use 0.45 micron filter but when we prepare and filter the disinfectant solution we use 0.22 micron filter. During batch preparation of SVP, LVP and liquid injections we also use 0.22 micron pore size filter for filtration of batch. The reason behind these questions is the purpose of using these filters. Being a microbiologist, I will explain you every aspects of this concept. First let we understand the morphology of the filter paper with particular pore size. Actually membrane filters are not having the single uniform sized holes passing from top to bottom , but they are ramification of channels through their whole thickness. So, because of morphology of filters its not possible for microorganism to pass thorough the filter. Therefore a filter of 0.45 micron size can retain large number of microbial cells smaller than the 0.45 micron. In microbiology we perform sterility testing to check any viable contamination in product/sample by observing turbidity in the SCDM (Soyabean casein digest medium) or FTM (Fluid thioglycollate medium) media. If viable contamination is present in the sample then it could be retained on the filter paper during sample filtration and during incubation we could detect that contamination. But what happen if we can't detect the contamination which is present in the product or during sterility testing if we unintentionally destroy the contaminating microorganisms which were already present in the sample. It will leads to false negative results which means contamination was present in the original sample but because of our testing problem or errors we couldn't detect the contamination in the product. That might cause release of sterility failure batch in market. Here in sterility testing our priority is to detect the contamination if present in the product. That is also mentioned in the pharmacopoeia that the test must be carried out under aseptic conditions designed to avoid accidental contamination of the product during testing. For achieving these conditions, a grade A laminar airflow cabinet or an isolator is recommended. The test environment has to be adapted to the way in which the tests are performed. Precautions taken for this purpose should not adversely affect any microorganisms, which are to be revealed in the tests. The test is designed to reveal the presence of microorganisms in the samples used in the test.During sterility we apply vacuum for filtration of sample, if we use 0.45 micron filter then microorganisms could be easily retained on the filter paper and the applied vacuum will not have impact on the viability of the microorganism involved in the test but if we use 0.22 micron filter paper stringent pore size and applied vacuum leads to damage of microbial cell which will not further recover during the incubation time. That's why we use 0.45 micron pore size filter for sterility testing. But during filtration of disinfectants or any liquid batch we use 0.22 micron pore size filter because in that our main purpose is to get sterile solution by removing the contamination from the solution whether live or dead it doesn't matter but the thing matters is that the solution must be sterile. Filtration is one of the method of sterilization. So, by filtering through 0.22 micron filter all form of contamination could be removed. That's why we use 0.22 micron pore size filter for filtration

How to do documentation in aseptic area?

Autoclavable Munising Paper

We all know ,that in documentation  is very important in  pharma industry  we use A4 size paper for documentation

"Paper should is main source of contamination in sterile area-

so how can we do documentation without contaminating our clean rooms "

Autoclavable munising paper is widely accepted for documentation in aseptic area

Stationery

The polymer impregnated substrate surrounds and bonds each individual cellulose fibre resulting in a cleanroom paper. The cellulose fibre core provides true paper characteristics giving problem free writing, printing and photocopying. Munising LP is auotoclavable, and benefits from extremely low static build-up and particulate generation.

Features:

• Munising LP is Latex Free
• The paper has a high degree of chemical resistance. The maximum loss of strength was 21% after soaking in the following 5% v/v H²SO4 2% w/w NaOH, Acetone, Ethanol and water. Tensile test on air-dried sheets.
• Munising LP can be sterilised by gamma irradiation, ETO or steam without seriously impairing the sheet. The particle count remains at the normal, low level.
• Microbe Testing - The yielded four colony forming units (CFU) according to micro pore filtration methodology and zero CFU according to Rodac plate methodology.
• The paper has a flammability rating of "moderately flammable" Classification 2, according to the National Fire Protection agency (NFPA-702)
• Using tests similar to those methods described in Federal Substances Act, CFR 16, Section 1500.41, it was determined that Munising LP would not be classified as primary skin irritant.
• Tests from NAMSA state that the paper is non-cytotoxic (MEM elution with l929 mice fibre blast cells).