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Biological contamination

One of the most common problems faced by researchers who use cell culture is biological contamination. This can be either by other cell lines or microorganisms used for research, or environmental bacteria, yeast, and viruses.

It is impossible to completely avoid contamination, but using the aseptic technique and identifying the major sources of contamination can reduce the risk.

Contamination is usually easy to spot upon microscopic observation of the cell culture. Although a decontamination process can be followed, in the case of a contamination event the safest and most convenient way to proceed is to discard the cells and begin a new culture.

Two merged images. The first figure shows how bacterial contamination progresses. Three images are labeled A, B and C from left to right. Image A shows uncontaminated cells. Image B shows how the cells start to be contaminated, circular bodies start appearing. Image C shows a fully contaminated sample of cells, where they can barely be seen. The second image is a comparison between two bluecap bottles containing healthy cells and contaminated cells. The bottle with contaminated cells shows a more cloudy sample.

Figure 1: (1) Examples of bacterial contamination progression. (A) Uncontaminated cells; (B) Initial contamination; (C) Contaminated cells. (2) Healthy cells (A) and contaminated cells (B)

Antibiotics in cell culture

Antibiotics should only be used when necessary and only for short periods of time and removed from the culture as soon as possible. Continuous use of antibiotics in cell culture is not recommended, as it encourages the development of antibiotic-resistant strains and allows low-level contamination to persist, which can result in contamination once the antibiotic is removed from media, as well as hide mycoplasma infections. Also, there is a risk that some antibiotics might cross-react with the cells and interfere with the cellular processes under investigation or the compounds being tested.