Contamination in CHO cell ? - (Apr/25/2012 )

Hi:
Revived an old CHO cell line (1992!) from N2. Grew nicely in for several passages (3 weeks) and then suddenly the media becomes yellow and lots of visible particules. Under 100x mic, these appear as suspended clumps, large and small (pls see photo).
Checked the unused media, no growth after 2 days. Made fresh media and revived another vial that was frozen 2 weeks ago. The 2nd lot gave the exact contamination after 2 weeks.
Other cell lines growing in the lab at the same time using the same FBS aliquots appear normal.

I will throw this out and restart another vial from another batch in N2. But I want to know more to avoid this happening again.
Could this be yeast contamination? How to test if my other lines have it?

Thanks for your help!
Moorlook

This does not seem like yeast contamination to me... yeast contamination usually looks like small round spheres, sometimes grape-like (check http://www.invitrogen.com/site/us/en/home/References/gibco-cell-culture-basics/biological-contamination/yeast-contamination.html). Your clumps remind me of DNA smears that appear after electroporation. It could also be a fungi of some sort. I would clean the incubators thoroughly with pharmacidal, start off with a new lot of FBS and media and hope for the best. Good luck!

Its hard to say, given the photo is blurry, but I'm thinking fungus.

To avoid it happening again, make sure that you are using correct aseptic technique. If you are unsure of what this entails, you should find someone who has many years experience in tissue culture (and who very rarely experiences contamination) to show you and then watch you.

Most CHO cells will grow with Pen/strep as well. You could add this to your media.