Probiotic CFU Explained

It is difficult to measure the number of live bacterial cells in a probiotic product so colony forming units (CFU) are determined instead. A CFU may represent one cell or several or more cells depending on the probiotic being evaluated. For example, a particular strain may form in short chains containing several cells, say 3 cells on average, and a single CFU would develop on a Petri dish from 3 cells not one. In this case the actual number of live cells represented would be approximately 3 times the CFU count. In another example, a particular strain of the probiotic Bifidobacterium lactis that forms as both single cells and clumps of 2-5 cells (as seen under a microscope) will produce CFU resulting from as few as one cell or as many as 5 cells. It becomes apparent that the determined number of CFU is partly a function of how a sample is prepared before analysis, samples mixed in a stomacher machine (simulates stomach motility) will usually test higher than samples shaken by hand.

A CFU is a bacterial colony that grows to visible size on a Petri dish containing a suitable agar. In the case of probiotics, MRS agar is used and the plates (Petri dishes) are incubated at body temperature (37 C) for 2-3 days or until visible colonies develop. Typically, a sample of a probiotic product (usually 1.00 grams) is diluted multiple times in sterile buffer or peptone to achieve an estimated strength of 30-300 CFU per milliliter. One millimeter of this diluted sample is then pipetted into a sterile Petri dish and molten MRS agar is poured over the sample followed by gentle mixing after which the agar is allowed to solidify before incubation. After incubation the colony count is determined, multiplied by the dilution factor, and the total CFU per serving is reported. This process is called plating the sample or making a plate count.

It is important to mention that it is not possible to differentiate different species or strains of probiotic bacteria from the appearance of their colonies. Probiotic colonies are usually round or disc shaped, 1-5 mm in diameter, and  tan or cream colored on MRS agar. So, when a multi-species probiotic product is plated only a total CFU count can be obtained. We have researched this in our laboratories at Master Supplements, Inc. and have found that an approximate determination of Lactobacillus count to Bifidobacteria count can be made in a mixed sample be incubating duplicate sets of plates aerobically versus anaerobically; here both the Lactobacilli and the Bifidobacteria grow anaerobically while only the lactobacilli grow aerobically. This technique is still under development.

Importance of taking multi-billions of probiotic CFU per serving

There are about 100 trillion live microorganisms in he human intestinal tract, most congregate in the lower ileum of the small intestine and the upper colon. Many have not been identified or characterized, some are beneficial while others are outright harmful or potentially harmful. Candida yeast, for example, is present in most of us but is held back from becoming infective by billions of  bacterial competitors. When antibiotics arrive on the scene the overall competition is reduced and the Candida cells morph into infective agents. To stifle this nasty scenario and create a positive balance between probiotics and other microorganisms takes multi-billions of probiotic CFU/day. Ten billion CFU/day is now accepted by industry leaders as the minimum effective dose (M.E.D.). This is one case where more is better.

Most of the probiotic literature is filled with studies employing less than 10 billion CFU per day, and significantly positive results have been hard to achieve in many of these studies. Good strains or not this is simply not enough dosage to consistently effect positive results. The researchers behind these studies always write: “More research is needed.” Actually, in many of these cases all that was needed was more dosage. To be specific, more dosage that was delivered alive through stomach acid into the small intestine!

Theralac probiotic 30 billion CFUSo, an effective number of CFU must be from clinically tested probiotic strains that can be delivered alive through stomach acid into the small intestine. This is not an easy trick as stomach pH can be as low as pH 1.5 and residence time can range from 1-3 hours, long enough to kill most probiotic strains. Consumers need to look for high strength probiotic products that can assure live delivery through the stomach. What is high strength?  It’s somewhere between 10 – 40 billion CFU per capsule (serving); and among probiotic industry efficacy leaders, products delivering these dosages are working best. Not surprisingly these products are not the industry leaders in total dollar sales. Heavily advertised products that have either one or two probiotic strains at less than 2 billion CFU per capsule are currently winning the sales race, which is analogous to treating an elephant’s headache with a baby aspirin.

Two probiotic products from Master Supplements, Inc. are among the industry’s high strength leaders in performance: Theralac® and TruFlora®. Theralac® contains 5 clinically tested probiotic strains at 30 billion CFU/capsule, TruFlora® contains 3 probiotic strains and two enzymes at 15 billion CFU/capsule. The CFU total for each strain is stated on the labels.

Both products contain buffered-alginate gel protection for acid-proof delivery (2 US Patents) and specialized prebiotic stimulation with LactoStim® (4 US Patents). Both products are packaged in amber glass bottles with Totally Inert Packaging (TIP™) and are guaranteed through expiration. Full Quality Control analysis is available online by lot number.

Randolph S. Porubcan, MSc
Consulting Biochemist