Is it possible that under daily change of media, a contaminated cell culture may manifest no visual signs of contamination? If so, when the cells look healthy and normal, is it safe to use these cells to conduct experiments?
Frequent media changes will conceal cell culture contamination. The most obvious change in cell culture flasks when cultures become contaminated is a turbid, cloudy appearance to the media, along with a pH change (observed by a color change in phenol red) that is not typical. This will be masked by frequently changing the media. That said however, if you use contaminated cells for experiments, you are corrupting your experiments. You will have non-reproducible data from apoptotic/necrotic cells.
Best of luck!
Dear Paikwin Li
Check this previous RG discussion:
https://www.researchgate.net/post/How_can_I_prevent_cell_culture_contamination
Yes, frequent media changes do conceal cell culture contamination. In cases like bacteria contamination, you will identify the signs of cell culture contamination real quick with cloudy appearance, change in pH and visible "vibrating" bacteria under a microscope. However, in cases of certain fungal contamination, it may require a longer duration of time and frequent media changes prolong this period. Signs of contamination are not visible as the number of contaminants in the media is low.
I would recommend you not to conduct experiments with contaminated cells or 'suspected' contaminated cells as there are many factors that will influence your final outcomes (for instance, are the cultured cells under stress to compete for nutrients? do the presence of contaminants produces toxin or hormones that affect growth of cultured cells? are the growth of cultured cells consistent throughout your work?, etc.)
The quickest way is to cross check with Hoechst staining. If there is any blue staining on areas which are not the nuclei of the cultured cells, then it may be the nuclei of the contaminants! There are also many kits available to detect fungal or yeast contamination. Good luck on your work.
Changing media constantly and 'washing' the cells when detached would help but if you have more vials stored is preferably to thaw another one and avoid contamination from the begining.
Good luck!
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