I had plated 10% FBS media to check for contamination and observed floating tree-like structure when checking the flask 15 days later. I had checked this flask daily initially and observed no growth until much later on. It seemed to resemble mycobacterium avium-intracellulare conntamnination whiich I read about here: https://link.springer.com/article/10.1007%2Fs11626-008-9143-8

I am now concerned about my cells. I had observed bacterial contamination in one set of flasks a few weeks ago, but not in the other flasks. Since then I have not observed contamination at all, but this type of contamination is slow-growing and difficult to detect when media if being changed regularly.

I want to know how common this type of contamination is as I have not found that much cell culture literature on this. I wanted to know if anyone has noticed this contamination in their on samples and how quickly they noticed it in serum media flasks containing cells. Has anyone observed this in 2-3 days? Or mostly after a week or so?

Thank you for reading.