Probiotics and Prebiotics

Probiotic production and consumption have been rapidly increasing due to their potential health benefits. Probiotics are “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host”. Health benefits of probiotics are strain-specific and are dose-dependent. Hence, it is essential to include the correct strain names and the viable cell count throughout the shelf life on probiotic product labels. A tool is needed for quick and accurate identification and enumeration of viable cells in probiotic products. PCR based methods are the most commonly used methods for food diagnostics because they are quick and sensitive. Viability PCR is a technique that uses intercalating dyes to intercalate to DNA of membrane-damaged cells so this DNA cannot amplify in a PCR reaction. In this study, viability PCR was used for the enumeration of probiotic strain Lactobacillus casei Lc-11 using strainspecific primers. The effectiveness of PMAxx was proven by its ability to differentiate between viable and heat-killed cells. The linear dynamic range was established between 3.7*105 to 37 genomes. The LOD was determined to be equivalent to 37 genomes (corresponding to 18.7 CFU). The reaction efficiency averaged to 101%. R square values were >0.99. The RSD% for repeatability and reproducibility averaged to 0.4% and 1.9%, respectively. Bacterial counts of Lc-11 products were determined using viability PCR and compared to the standard plate count method. The counts from both methods were highly correlated with R square >0.99. This protocol enables accurate and fast probiotic enumeration.