Contact us :customer@cti-eu.com
Views: 5 Author: vivi Publish Time: 2025-06-13 Origin: Site
Contamination in cell culture is one of the most common problems encountered in cell culture laboratories and can sometimes lead to serious consequences. Contaminants in cell culture can be divided into two major categories:
l Chemical contaminants, such as impurities in media, serum, and water, endotoxins, plasticizers, and detergents;
l Biological contaminants, including bacteria, fungi, yeasts, viruses, mycoplasma, and cross-contamination with other cell lines.
Although contamination cannot be completely eliminated, its frequency and severity can be reduced by fully understanding its sources and adhering to good aseptic techniques.
Major Types of Biological Contamination
Bacteria are ubiquitous single-celled microorganisms. They typically measure a few microns in diameter and can take on various shapes, from spherical to rod-shaped or spiral. Due to their omnipresence and rapid growth, bacteria, along with yeasts and molds, are the most common biological contaminants in cell culture.
Detection:
Bacterial contamination can usually be detected by visual inspection within a few days after infection. Contaminated cultures often appear cloudy (turbid) and may develop a surface film. A sudden drop in pH is also frequently observed. Under low magnification, bacteria appear as small moving particles between cells, while high magnification reveals the shape of individual bacteria.
Molds are eukaryotic microorganisms that grow in a multicellular filamentous form known as hyphae. The network of hyphae, containing genetically identical nuclei, is called a colony or mycelium.
Detection:
Similar to yeast contamination, the pH of the culture medium remains stable in the early stages of contamination but increases rapidly as the infection worsens and the culture becomes turbid. Under a microscope, molds typically appear as filamentous structures, sometimes forming denser spore clusters. Spores of many mold species can survive in extremely harsh and uninhabitable environments during dormancy, only becoming active under favorable growth conditions.
Viruses are microscopic infectious agents that replicate only within host cells. Their extremely small size makes them difficult to detect in cultures and hard to eliminate from reagents used in cell culture laboratories. Because most viruses are highly host-specific, they usually do not affect the cultures of cells from species other than their host. However, using virus-infected cultures can pose serious health risks to lab personnel, especially when working with human or primate cells.
Detection:
Viral contamination in cell cultures can be detected by electron microscopy, immunostaining with a panel of antibodies, ELISA assays, or PCR amplification using appropriate virus-specific primers.
Mycoplasmas are simple bacteria that lack a cell wall and are considered the smallest self-replicating organisms. Due to their extremely small size (usually less than one micron), they are difficult to detect until they reach high densities and cause culture deterioration. Often, there are no obvious signs of infection in the early stages.
Some slow-growing mycoplasmas may persist in cultures without killing host cells but can still alter host cell behavior and metabolism.
Detection:
Chronic mycoplasma infection may result in reduced cell proliferation, lower saturation density, and aggregation in suspension cultures. However, the only reliable way to detect mycoplasma contamination is through regular testing using fluorescence staining (e.g., Hoechst 33258), ELISA, PCR, immunostaining, autoradiography, or microbiological assays.
Yeasts are unicellular eukaryotic microorganisms, typically a few microns in size (up to 40 microns in rare cases).
Detection:
Similar to bacterial contamination, yeast contamination causes cloudiness in cultures, especially in the later stages. The pH of the medium generally remains unchanged until contamination becomes severe, at which point the pH usually increases. Under a microscope, yeasts appear as single oval or spherical particles.
