Hey everyone,
I've been working with human mesechymal placenta stem cells in our lab. We isolate them directly from a polacenta taken from a C.section. We expand the cells and freeze them at P2-P3. After thawing the vials and growing them for avbout 1-2 passages the medium becomes opaque and the whole flask floor is covered with a net like culture. After confirming that it is a mixed bacterial infection, we removed all the samples and sterilised all the facilities and tools. We received a new placenta and did the same procedure. The contamination reoccured. It is important to note that all the solutions and technics have been used before and they resulted in good yield without any contamination signs, and, offcourse all the work is conducted under sterile conditions.
Do you have any ideas where can this contamination come from and how to deal with it?
NOTE: The red one is PI stained