Floating cells in adherent VERO culture - contamination? (Jul/27/2009 )

Hello,

I have a VERO cell line in culture and this is adherent. For a couple of passages now I notice there are cells floating around. This occures already at a confluence of 80%.

When I look closer at phase contrast 200* magnification I see very few black moving dots (hardly 1 per field of view). These are moving a bit in spaces between cells.

The medium still looks normal. Not cloudy yet. The medium does contain puromycin.

I think this is an early microbial contamination. But I have to know sure before I toss it because we really need this cell line at the moment and it is already scaled up.

I can not find anything on floating cells in adherent culture linked to contamination. But I think this is also an indication of microbial contamination

Does anyone know for sure that this is a contaminated culture?

It is impossible to definitively say that it is contamination without seeing the culture and/or further tests. Puromycin is a very strong antibiotic that causes cell death, I suspect that what you are seeing is cellular debris from non-resistant cells or precipitates from the FBS. If the population of black dots increases with time, there is a strong odour or the pH changes drastically it is likely to be bacteria.

bob1 on Jul 28 2009, 03:10 AM said:

Thanks for the respons

We culture them under serum free conditions. And I have this culture on 2ug/ml puro and already a lot of passages without PUR and with both cultures I see the floating cells. This is what worries me. The fact remains that small black dots that are moving are not abundant. SO maybe theculture is not contaminated. I will take my precautions and thaw an early passage with new media. And compare old and new.