All cell culture contaminants can be problematic, but in comparison to other types of bacterial and fungal contaminants, mycoplasma contamination is usually more difficult to detect. This is because Mycoplasma are very small and replicate at a slower rate compared to many other bacterial species.
The presence of Mycoplasma in your cell cultures can seriously affect the behavior of your cells, making your results unreliable and unreproducible. We understand how frustrating it is to discover that your cultures are contaminated, especially as you might have to set up another culture and/or repeat any experiments performed since the last negative mycoplasma test. However, if you wish to obtain accurate data that is as representative as possible of your model system, it is usually best to discard the contaminated cultures and set up new ones.
You can continue with your experiments from the last negative mycoplasma test. Review guidelines for sterile working, including keeping your equipment in the best condition to reduce the risks of mycoplasma contamination, for example, in your incubators and water baths. This will identify where you can improve your facilities and procedures, helping you to reduce the risks of future mycoplasma contamination.