Dear friends a group of microbiologists has recently condemned our sterility tests (for aerrobic, microaerobic and anaearobic bacteria) on some vaccine on the grounds that instead of using screw capped tubes or flasks we used 100 ml cotton plugged tubes?
For anaerobic culture and microaerobic cultures Thioglycollate medium was used.
Yours replies are important as it will be lesson to us to modify the techniques established and used in bacteriological culture techniques.
Cotton plugs do increase the risk for contamination quite a bit. How do you keep them sterile when doing transfers? The screw cap would be preferable when using thioglycollate media as tightening the tubes helps increase the anaerobic conditions. Loose screw tops work well for aerobic cultures, but the culture tubes with loose caps are ideal as they are easy to handle if doing transfers, and they remain sterile.
Dear Bhoj,
comparing to the most similar equipment - porous foam silicone stoppers for microbiology use, cotton wool stoppers have a number of disadvantages. To me, the main ones - cotton generate a lot of dust that carry bacteria and fungi spores, and wet cotton is a good substrate for growth of fungi and bacteria.
Vaccine test is a serious research, and laboratory must fit to highest standards of microbiology.
Alex
Cotton plugs do increase the risk for contamination quite a bit. How do you keep them sterile when doing transfers? The screw cap would be preferable when using thioglycollate media as tightening the tubes helps increase the anaerobic conditions. Loose screw tops work well for aerobic cultures, but the culture tubes with loose caps are ideal as they are easy to handle if doing transfers, and they remain sterile.
It is true that cotton plugs are not Ideal for high sensitive Research. and screwcaps are more reliable. However, for routine work cotton plugs are more suitable due to its Iow costing and easy availability.
Dr. Ghosh, You are making a good statement, and it is sad that cost is sometimes more important than protecting our research efforts. But I might also remind you that have some of the simple culture tubes (with loose caps) is inexpensive and they can be reused after autoclaving. Using cotton works, but be careful for contamination.
its good to use cotton plugs for routine microbiological works but for vaccine testing or other sensitive microbiological woks we need to use one time costing screw caps which can be reused after autoclave. Additionally its one time investment venture whereas in cotton plugs you rarely go for second time use or some time some workers do reuse them until their usability. you have to prepare them fresh every time and also as evidenced they are likely to cause of microbial contamination.
Dear all, many thanks to you for your replies, contamination is is realy big problem but I think when you are working in high end laboratories (BSL-3+) with all filtered air and clean room environment and also inform of flame, this should not be big issue. Moreover, I hope you will all agree that many more bacteria have been first isolated in pure culture by the scientists working using the cotton plugs rather than using high end devices as mentioned in your communications.
Moreover when cotton plugs are systematically wrapped with muslin cloth they can be better.
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