Assessing total viable bacterial count in commercially available probiotic dietary supplements.

Probiotics are live bacterial strains of the genera Lactobacillus and Bifidobacterium that are abundant in human intestines with numbers as high as 1011 cells/g of intestinal content. Probiotics and supplements containing probiotics attract considerable interest due to their claimed health benefits. The market value of this industry is anticipated to increase to $7.1 billion by 2026 (the current value is $5.8 billion). Some genera, such as Lactobacillus and Bifidobacterium species, are commonly used in yogurt products and many dietary supplements. The US Food and Drug Administration (FDA) categorizes probiotics as “Generally Recognized as Safe” (GRAS) so they are not regulated by the FDA. Thus, these products can be vulnerable to non-compliance, especially pertaining to the claimed viable bacterial counts. The objective of this project is to assess viable cell counts of bacteria in various commercially available probiotic supplements and compare those with the claimed values. Commercially available supplements containing Lactobacillus acidophilus and Bifidobacterium species were obtained from various online and local pharmacies (n=9 to date). Each sample was digested in a stomacher at 2300 rpm for 5 minutes in sterile Ringer’s solution, serially diluted and plated on De Man, Rogosa and Sharpe (MRS) and Bifidus Selective agar, and incubated under anaerobic conditions at 37°C for 72 hours. Viable colonies were counted and percentage difference from the expected count was calculated. So far, 75% of products had lower than specified viable counts and the remaining 25% of products exceeded the specified viable counts on the label. This is an on-going study