Contamination of cell cultures

There are various methods for detecting Mycoplasma contamination of cell culture. A sensitive polymerase chain reaction test with broad specificity for Mycoplasma species is our method of choice (8). There are several products available for the eradication of Mycoplasma species from cell lines. The effectiveness of the treatment will depend on the cells and involves trail and error. This is because some cell lines are very sensitive to the chemicals used to eradicate Mycoplasma and may become static or die during treatment. 

As mycoplasmal contamination of cell cultures is not always so obvious as bacterial contamination, it is important to 1) be aware of the effects of mycoplasmas on cell cultures, and 2) carry out routine tests for their presence. This is especially important as a contaminated culture may have 108 mycoplasma per ml, i.e. there may be 100 mycoplasma per cell. The mycoplasma often grow attached to the surface of the cell providing it with a prokaryotic coat. 

Contamination of cell cultures with fast growing cell lines such as HeLa has led to the emergence of incorrectly classified cell lines. These robust cells are capable of outcompeting slower growing cell lines and consequently take over. A study performed by MacLeod determined that 18% of the cell lines investigated harbored cross-contaminants. These cell lines were obtained from the source of origin. When working with cell lines it is of paramount importance to use those that have been authenticated. 

Mycoplasma contamination of cell culture systems continues to present major problems for monoclonal antibody production. Mycoplasma-positive cell cultures are themselves the major source of infection. It is recommended that all myeloma cell lines be tested for mycoplasma prior to fusion. If a hybridoma culture is considered irreplaceable, it is possible to eliminate effectively the mycoplasma contamination by injecting the hybrids into mice. The animal s immune system will destroy the infection and effectively clean up the cells. The mycoplasma-free cells are then recovered by draining the ascites fluid. Drug treatment is also an effective method to decontaminate hybrid cells from mycoplasma infection. 

Stanbridge (1971) has thoroughly reviewed the problems intrinsic to mycoplasmic contamination of cell cultures. Following such contamination we have found that our cultures acquire a number of unusual traits, most of which are predictable in accordance with Stanbridge (1971). Briefly stated, these are the following ... 

---