Death (pt. 1)   Leave a comment

I had to throw out all my cultures today- there was evidence of a bacterial infection.

I suppose I was due; my technique has been a little sloppy lately.

The cultures don’t have an immune system- they are defenseless against all the garbage in the air- bacteria, virii, mold, yeast, etc. etc. Because of this, cell culture is carried out under sterile conditions, using a special culture hood- not only is the air circulated through a HEPA filter, but there’s also a germicidal bulb that kills via ultraviolet light. We also use *lots* of ethanol, bleach, biocides, etc. etc.

Even then, I was getting contamination every month or so- the lab is in the Physics Department of an old dusty building- so I opted for one final line of defense: antibiotics, added to the culture media.

We use a combination of penicillin/streptomycin and gentamicin. The pen/strep protects against one type of bacteria, while gentamicin protects against the other main type. I also have some fungicide for use as needed.

Adding antibiotics chronically can have several bad effects- one, it masks an infection. Bacteria can live just fine within a cell- they are competing for the culture media, they don’t ‘eat’ the cells- and when they erupt from a dead cell, they get killed by the antibiotics. So a culture can be infected and appear perfectly normal. Which is what happened to me.

So today, I tossed all the cultures, cleaned the incubators and hood, and made some fresh media- without antibiotics. A sample of that media is now spending the night in the incubators to determine if they are contaminated (or if the media itself has contamination), and then I’ll thaw recently frozen cells, incubate them with the antibiotic-free media, and see if the frozen cultures are clean. If so, we can get back on track. If there’s a problem with the frozen cells, well….

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Posted September 14, 2010 by resnicklab in Physiology, Science

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