Anyone with much experience in culturing cells knows something about contamination, usually from personal experience. For the lucky scientists, the contamination only impacted a few plates, but it can also take over an entire incubator. Sticking to a set of rules in using an incubator, though, reduces the odds of ending up with a contaminated one.

It’s easy to get a feel for the scope of the problem by searching online for incubator and decontamination. In a Google search on July 5, 2019, that combination of words returned more than 170,000 hits, including nearly 5,500 videos. Features in incubators—from HEPA filters and easy-to-clean surfaces to decontamination cycles—also indicate the challenge. But here’s the thing: One misstep by a scientist can make it easy for an unwanted microorganism to outsmart the most clever features and gadgets designed to keep bugs out of cultures.

To get some top tips on keeping an incubator clean, we talked with Alison Killilea, scientific facilities manager in the department of cellular and molecular biology at the University of California, Berkeley.

Pro tips

“We are a facility,” Killilea explains. “So we work much differently than most labs—we are very uniform in what we do and how we train.” She adds, “We don’t use antibiotics and rarely see contamination.”

Even the most careful training, though, cannot eliminate all risk of contamination. “On the occasion when we do see contamination, it’s usually yeast,” Killilea says. “I think it typically comes from people not using ethanol to disinfect their gloves.”

To keeps such instances of contamination to a minimum, Killilea and her colleagues combine technology and technique. “To reduce the risk of contamination, we use copper-lined incubators, lots of ethanol, and we don’t use antibiotics that could mask an infection,” she says. “As soon as we see a contaminated plate, we wrap it in a plastic bag and place it in the biohazard trash.”

Be extra careful. That’s a good mantra to keep in mind. Don’t take unnecessary risks. For example, when talking about finding a contaminated plate, Killilea says that “some labs bring the plate back into the hood and add bleach to it, but I think this just increases your risk of spreading the contamination.”

Speaking of spreading contamination, forget all that you learned in kindergarten—do not share! As Killilea says, “I think a good practice for reducing the risk of contamination is to not share reagents with lab mates.” She adds, “Isolate your reagents so you don’t spread contaminants.”

The key for keeping incubators free of contamination as much as possible depends on developing a set of procedures, training everyone using the incubators on those procedures, and then adding some quality control that keeps people practicing the procedures as designed.

Don’t count on the equipment to do all of the work. It won’t. The equipment can reduce the odds of contamination. Cleaning cycles on a device can even help a lab clean up a contaminated incubator. In the end, though, the personnel in the lab are the most likely cause of contamination and the best line of prevention.

Mike May is a freelance writer and editor living in Texas. He can be reached at [email protected]