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Pharmachem Moves to Measure All “Viable” Cells in Probiotics vs. CFUs


Pharmachem Laboratories, Inc., (Kearny, NJ) announced that it is now using flow cytometry to more accurately and quickly measure the viable cells in probiotic formulas as opposed to the traditional plating method which measures only colony forming units (CFUs).

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According to Alexis Collins, director of scientific affairs for Pharmachem, at least one-third of the company’s probiotics customers now request flow cytometry for unique formulations. “We offer many formulations using probiotics, and plating is just too variable to accurately measure probiotics post-formulation,” she said.

With flow cytometry, probiotic cells are tagged with fluorescent “markers,” which allow each cell to be counted by a laser as they pass through a tiny tube. The technology provides a method for counting live, injured and dead cells in a formula. “You will often see higher numbers of viable cells versus CFUs, because flow cytometry measures all viable cells,” explained Collins. “At times, a probiotic ingredient can contain up to 50 percent viable, but non-culturable, cells (VBNCs). The total count of viable probiotic cells equals CFUs plus VBNCs.

“Counting CFUs has been the standard measurement—but it does not count all efficacious cells,” Collins added. “VBNCs are not measured via plating, only cells that are ‘happy’ enough can form colonies in that specific media environment.”

Pharmachem provides probiotics customers with total viable cell counts in active fluorescent units (AFUs) along with CFU counts. “Another attractive benefit to flow cytometry is the speed-to-results,” said Collins. “Plating typically takes days, while flow cytometry gives you results in triplicate in under an hour.”

Flow cytometry has been used as a validated cell counting technique for decades, but was first adapted for probiotic counting by Pharmachem’s partner, Probiotical, Novara, Italy. It is the enumeration method they recommend all customers use.

“Flow cytometry method is universal and independent of the species analyzed, so it is equally valid for L. acidophilus and B. breve, for example,” explained Probiotical’s Dr. Marco Pane. Traditional plating relies on methods that differ between species, genus, and even suppliers and laboratories. Since December 2015, the application of Flow cytometry for lactic acid bacteria enumeration has been published as an official International Standard (ISO) method (ISO 19344:2015 – IDF 232:2015).

For more information, visit www.pharmachemlabs.com.