Hello,

I'm working with primary mouse osteoblasts obtained through calvarial prep and both my coworker and I are having issues with a strange contamination that neither of us have seen before (she's been working in this lab for almost 20 years).

The media looks slightly cloudy almost like there is a film inside it but if you swirl it it kind of disperses. Under the microscope there are no recognizable bacteria or yeast, it just looks like a lot of cellular debris. Unfortunately I don't have a picture of it but next time I have a well that's contaminated I'll post a picture as well. I've tried to cover every base and we cannot figure out what is causing it. Here are some details:

- So far only mouse osteoblasts seem to be affected; we work with human osteoblasts less frequently but in the same incubator

- My coworker and I use different incubators, different media, FBS, and penn/strep (same company, different bottles), different mice

- Only one or two wells in the 6 well plate or chamber slides will be contaminated, despite all wells being in the same plate, getting the exact same media, in the same hood, etc.

- We recently had our tissue culture hood checked and it passed inspection, afterwards I did a really deep cleaning of the hood and both incubators but the issue continues even though we got rid of all contaminated cells prior to this cleaning

I welcome any ideas because I'm getting desperate.