Hi I have a question, I was reading some articles about different conditions for storing aliquots of antibiotics for use in culture media. But I would like to ask you, according to your personal experiences, have you had problems storing antibiotics at -70 or -80 ºC? I am specifically interested in penicillin, streptomycin, blasticidin S, ampicillin and amphotericin B. Would you recommend storing them at -80 ºC to better preserve their properties and even extend their shelf life?
Thank you in advance!
Hi, I used to store the antibiotics ( Ampicillin) at -20 when I was doing my Ph.D., and it works perfectly in the culture media; I think storage at -80 used to store stuff for a long time with glycerol to protect them from ice crystals. Good luck with your research
It all comes down to chemistry. The colder it is the slower chemical reactions happen (especially endothermic reactions). So yes storing your aliquots at -80ºC will prolong their shelf life compared to -20ºC but you will also need to factor in cost since colder freezers chew more power so are more expensive to run. This means you need to offset the cost of just buying in a new batch of antibiotics over the cost of keeping them colder.
Another factor you should consider is how the antibiotics degrade. Usually this is by oxidation so you can prolong the shelf life further by purging the atmosphere in the aliquot with argon or nitrogen. Note this would then need screw top vials since regular Eppendorfs are not great at preventing gas exchange.
Hi,
There might not be a generalized answer to the question as it will depend on the physicochemical properties of the antibiotics. It could be class-specific. For 11 beta-lactam antibiotics, it was experimentally found that storing at -70°C gave better stability than storing at lower temperatures. Storage at -25°C is suitable for up to 3 months for many, but not all, even within the beta-lactam class.
Please refer to the article - https://doi.org/10.1128/jcm.21.3.366-370.1985
The recommended antibiotic storage temperature is -20 degrees Celsius for powders and solutions. However, the stability of some stock solutions necessitates that they be stored at -80°C. For instance, after a week in the freezer, ampicillin solutions deteriorate by 13%. Antibiotics can be stored safely as dry powders. The antibiotic becomes more unstable when it is dissolved in sterile water or other solvents (most commonly, 100% ethanol). That's why you need to store antibiotics in aliquots at -20°C and agar plates at 4°C. Most antibiotic supplies can be kept at -20°C for at least 6 months; however, investigations have shown that penicillin-derived antibiotics and tetracyclins are only stable for 3 months.
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