I work with cell cultures. A few weeks ago I decided to control the reagents that we use in our laboratory and aseptic conditions in BSCII, incubator and laboratory room.
I made three 24well plates with reagents (Medium complete, only Medium, FBS, Medium + antibiotic and etс.). One plate I put in incubator, one I left on the table in BSCII and one I put on the table in laboratory room.
In 24 hours I checked plates and saw under the microscope:
- contamination in whole plate from BSCII (cocci)
- contamination in whole plate that stood on the table in the room
- from incubator plate was clean
So how is it possible? I worked in BSC with reagents and then in incubator plate stayed clean, but plate in BSC - contaminated. Then instruments, which lying in it must be contaminated too (I don't believe that UV ''save'' tips and tube during 1 hour before work if in BSC such contamination). Furthermore, in cells with only Medium (in plates from room table and BSC-table I saw something similar to a yeast. And I remember, in incubator whole plate was clean!
I made also 3 flask T-25 with complete medium and in 24 hours I saw, that flasks from tables were also contaminated. So I guess that, probably, the reagents are contaminated, because it's very difficult to imagine that something can get into flask through HEPA-filter.
But what is it the organism, that grows at room temperature and don't grow in incubator? Or, maybe, it's somethinge else.
Please, I'm waiting for your suggestions, because I don't understand, suorce of contamination.