Kearny, NJ—Pharmachem Laboratories, Inc., based here, has announced that it is moving away from measuring colony forming units (CFUs) in its probiotic formulas, instead utilizing flow cytometry which the firm says more accurately and quickly measures the viable cells in probiotics. This is a process that according to Alexis Collins, director of scientific affairs for the firm, one third of its probiotic customers now request for unique formulations.

“Plating is just too variable to accurately measure probiotics post-formulation,” explains Collins. The difference between the two methods is that flow cytometry measures all viable cells rather than just those that form colonies. “At times, a probiotic ingredient can contain up to 50% viable, but non-culturable, cells (VBNCs),” she says. “The total count of viable probiotic cells equals CFUs plus VBNCs.”

Flow cytometry does this by tagging probiotic cells with fluorescent markers that allow each individual cell to be counted by a laser as they pass through a tube. This makes it possible to count live, injured and dead cells in a formula. Viable cell counts are expressed in Active Fluorescent Units (AFU) along with CFUs.

Besides providing a more accurate count of viable probiotic cells, flow cytometry is also much faster compared to the plating involved with measuring CFUs which can take days, while the former takes under an hour. While this method has been used for decades to count cells, it was first adapted to probiotics by Pharmachem’s partner Probiotical, Novara, Italy. While traditional plating methods differ depending on genus, species and suppliers, flow cytometry is universal.