The presence of microorganisms can inhibit cell growth, kill cells, and lead to inconsistent results. Contamination of cell cultures can occur with both cell culture novices and experts.
Potential contamination routes are numerous. For example, cultures can be infected through poor handling, from contaminated media, reagents, and equipment (e.g., pipets), and from microorganisms present in incubators, refrigerators, and laminar flow hoods, as well as on the skin of the worker and in cultures coming from other laboratories.
Bacteria, yeasts, fungi, molds, mycoplasmas, and other cell cultures are common contaminants in animal cell culture. To safeguard against accidental cell culture loss by contamination, we recommend freezing aliquots of cultured cells to re-establish the culture if necessary (see Freezing and viability staining of cells).
The characteristic features of microbial contamination are presented in the table Characteristic features of microbial contamination. The presence of an infectious agent sometimes can be detected by turbidity and a sharp change in the pH of the medium (usually indicated by a change in the color of the medium), and/or cell culture death. However, for some infections, no turbidity is observed and adverse effects on the cells are not easily observed.
Cell cultures should be routinely evaluated for contamination. Mycoplasmal infections are one of the more common and difficult-to-detect infections; their detection and eradication are described in further detail below.
Characteristic features of microbial contamination
|Change in pH||pH drop with
| pH change with
|Shimmering in spaces
between cells; rods or
cocci may be observed
|Round or ovoid
particles that bud off
|Thin filamentous mycelia;
sometimes clumps of spores