2. Yeast and Fungal Contamination
As with bacterial contamination, yeast and fungal contamination can originate from internal and external sources, such as staff, equipment, or unfiltered air. In addition to microbial cultures, yeast can be detected by their smell and visual cloudiness, while seeing particulates or mycelia is a sign of fungus. Prevention tactics for both are similar to those for bacterial contamination, except antimycotics should be used instead of antibiotics.
3. Viral Contamination
Unwanted viruses can enter the lab through original tissues, serum, staff, and cross-contamination. Viral contaminants are typically detected from co-cultivation, PCR testing, electron microscopy, assays, and in vivo testing. Prevention tactics include ultrafiltration, chemical treatments, gamma-irradiated serums, vapor-phase LN2 storage of cell line stocks, and using animal-free products when possible.
4. Mycoplasma Contamination
Mycoplasma infection is a big problem and has been for a while. It's estimated that between the 1970s and 1990s, up to 15% of U.S. cell cultures were contaminated by mycoplasmas. Typically, contamination derives from contaminated cell lines, serum, media, staff, or biosafety cabinets.
Many infections can be identified through microbial cultures, Hoechst stains, specialized kits, or PCRs. Ultrafiltration, antibiotics, use of animal-free products, and vapor-phase storage are all helpful prevention techniques.
5. Cellular Contamination
No story exemplifies cellular contamination better than the HeLa saga. In the 1960s, a researcher discovered that 100% of that era's commonly used cell lines had been incidentally replaced with cells from the Henrietta Lacks cell line. As that anecdote illustrates, widespread cellular contamination can occur through cross-contamination of cultures. It can also happen due to cross-use of media from different cell lines and biosafety cabinets.
Generally, the only way to detect cellular contamination is through cell authentication, but there are many best practices to prevent it, such as working with only one cell line at a time, conducting thorough cleaning, and using vapor rather than liquid storage.
Aseptic Techniques Are Most Important
Biological and chemical contamination can pose serious risks to all stakeholders in science, from the lab technician to the individual in charge of the lab's bottom line to the patients who depend on products every day. As you work to avoid contamination in your lab, remember that there's no substitute for good aseptic techniques.
Those techniques — combined with the strategic use of antibiotics and antimycotics, cell repositories, and a robust contamination monitoring program — can protect you and your precious cultures from the world's unwanted tiny invaders.