We have an issue in our tissue culture room. There are two of us with suspension cell lines, and two with adherent. None of us use antibiotics at the moment in our cultures. Just before Christmas, I noticed tiny 'fidgeting' black dots and also larger, more spherical objects that almost appear to spin in multiple directions. Usually all assays are done in flasks so I hadn't noticed this before, you can only see them when you plate out the cells after one or more days on the highest magnification.
After I saw this, everyone else checked and the other suspension cell line was crawling with them, but the two adherent cell lines only had minimal numbers. We all use different media and FCS and have plated these out and they are clean.
What confuses me is how the suspension cell lines appear to carry such higher numbers than the adherent, we have tried growing the bugs in multiple broths and plates but nothing grows. It does not turn our media cloudy. We have cleaned the incubator, hoods and water bath but the problem remains.
As we use neutrophil-like cell lines we cannot do our assays as they are quite happily munching up whatever the black dots are, and also lysing. I need some advice as to how to get rid of this problem??