Biological contamination

Biological contamination is the most common problem encountered in cell culture laboratories, sometimes with very serious consequences. These contaminants include bacteria, molds, yeasts, viruses, mycoplasma, and cross contamination by other cell lines. While it is impossible to eliminate contamination entirely, it is possible to reduce its frequency and seriousness by gaining a thorough understanding of their sources and by following good aseptic technique. A contamination event could be noticed mainly by visual observation, but there are other ways such as PCR or fluorescent dyes. Although a decontamination process can be followed, in the case of a contamination event the most convenient way to proceed is to discard the cells and begin a new culture.

Figure 1: Examples of biological contamination. (A) Bacterial contamination. (B) Yeast contamination

Use of antibiotics

Antibiotics should never be used routinely in cell culture, because their continuous use encourages the development of antibiotic-resistant strains and allows low-level contamination to persist, which can develop into full-scale contamination once the antibiotic is removed from media, and may hide mycoplasma infections and other cryptic contaminants. Furthermore, some antibiotics might cross-react with the cells and interfere with the cellular processes under investigation. Antibiotics should only be used as a last resort and only for short term applications, and they should be removed from the culture as soon as possible. If they are used in the long term, antibiotic-free cultures should be maintained in parallel as a control for cryptic infections.