How to Eradicate Mycoplasma in Your Lab: A 5-Step Protocol From 30 Years of Expertise

This is the most impactful infrastructure decision you can make, and it’s the one most often compromised in shared laboratory facilities. The CO₂ incubator is not just a warm box — it’s an enclosed ecosystem with internal fans, air currents, and humidity that actively circulate particles between every flask, plate, and dish stored inside.

When you share an incubator with another lab, you are placing the integrity of your entire cell culture program in someone else’s hands. If a researcher from a neighboring lab introduces a contaminated flask — even unknowingly — the incubator’s internal air circulation will distribute mycoplasma-containing particles throughout the chamber. Research has demonstrated that airborne particles and aerosols generated during culture manipulations are among the greatest sources of microbial contamination, and incubator fans actively amplify this effect every time the door opens and closes.

The recommendation is absolute: dedicate one CO₂ incubator per laboratory. If complete separation isn’t immediately feasible, at minimum ensure that cultures from different labs are isolated in sealed containers within the incubator — never open plates or unsealed dishes alongside another lab’s cultures. But understand that sealed containers are a compromise, not a solution. True isolation is the only reliable prevention.

Additionally, implement a regular incubator cleaning schedule. Remove all vessels, shelves, and trays periodically, and decontaminate internal surfaces with proven disinfectants. PurMa Biologics manufactures a proprietary CO₂ incubator treatment specifically designed to maintain pathogen-free conditions inside the chamber — a critical complement to the physical isolation strategy.

The second most common route for mycoplasma to enter your lab isn’t through the air or from your skin — it’s through the front door, carried in a flask of cells from another laboratory. Published literature consistently identifies previously contaminated cell cultures from other research groups as the single largest external source of mycoplasma contamination. A single infected line, once introduced, can compromise every other culture in the facility within weeks.

Cell lines obtained from reputable repositories — such as ATCC, DSMZ, or other established biobanks — undergo rigorous mycoplasma testing before distribution and can generally be trusted. However, the reality of research is that many valuable and irreplaceable cell lines come from collaborator labs, core facilities, or legacy freezer stocks with uncertain provenance. These lines must be treated as potentially contaminated until proven otherwise.

The protocol is simple: every cell line from an external source gets quarantined in a separate incubator or sealed container and tested with the PurMa Mycoplasma PCR Detection Kit before it is allowed anywhere near your working cultures. No exceptions. It doesn’t matter how trusted the collaborator is, how reputable the institution is, or how urgently you need the cells. Test first. Introduce second. This single practice has prevented more contamination events than any other measure in cell culture history.

Testing incoming cell lines is essential, but it’s not sufficient. Mycoplasma can enter your cultures at any time — through contaminated reagents, through human transmission during routine handling, through cross-contamination from shared equipment. The only way to catch contamination before it compromises your data is through consistent, scheduled screening.

The recommended testing schedule is weekly. At an absolute minimum, screen every two weeks. Your testing should cover four critical targets:

Cell culture media — Test each batch of cell culture media, whether commercially purchased or prepared in-house using proprietary chemically defined media formulations. Contamination can be introduced during handling, aliquoting, or storage.

Fetal bovine serum (FBS) — Premium fetal bovine serum is a known potential vector for bovine-origin mycoplasma species, particularly M. arginini and A. laidlawii. Even reputable serum suppliers cannot guarantee 100% mycoplasma-free product without independent verification on your end.

Cell culture water — Water used in media preparation, washing, and other cell culture applications should be tested regularly. Contaminated water sources can introduce mycoplasma that persists through subsequent media preparation steps.

Cell supernatants — This is your most direct indicator. Testing the supernatant of your actively growing cultures tells you whether the cells themselves — the cultures producing your experimental data — are currently contaminated.

This step addresses the single greatest source of mycoplasma contamination in any lab: you.

The data is unambiguous. Over 80% of laboratory technicians carry mycoplasma in their oral cavity and oropharynx. The most commonly isolated species — M. orale, M. fermentans, and M. salivarium — are human commensals that colonize healthy individuals without causing symptoms. You don’t know you’re carrying them. You can’t prevent yourself from carrying them. But you can prevent them from reaching your cultures.

Wear a mask when checking cells under the microscope. This is the single most exposed moment in cell culture work. You’re leaning directly over your cultures, often for extended periods, breathing directly onto flask surfaces and the surrounding bench area. A mask — even a standard surgical mask — creates a physical barrier that dramatically reduces the transfer of oral mycoplasma to your workspace.

But masking alone isn’t enough. Mycoplasma that has already been deposited on surfaces can remain viable for four to six days, waiting to be transferred to your cultures via gloves, pipettors, or any other point of contact. Surface decontamination before each work session is essential.

Steps 1 through 4 target mycoplasma specifically. Step 5 broadens the defense to cover all pathogens — because mycoplasma is not the only contaminant threatening your cultures, and a truly clean lab requires comprehensive surface management.

The logic behind twice-weekly application is straightforward. Mycoplasma can survive on surfaces for up to six days. By sanitizing every three to four days, you ensure that no surface in your lab remains untreated long enough for deposited organisms to accumulate and pose a contamination risk. This creates an environment where even if mycoplasma is introduced — through a visitor, a new technician, or a momentary lapse in masking protocol — it cannot persist long enough to reach your cultures.

Think of it this way: Steps 1–3 prevent mycoplasma from entering and detect it early. Step 4 blocks the primary transmission pathway. Step 5 ensures that whatever gets through the first four layers doesn’t survive to cause contamination. It’s defense in depth — and it works.