Rapid identification and quantification of Lactobacillus rhamnosus–targeting real-time PCR using a TaqMan probe

Abstract

Lactobacillus rhamnosus is a gram-positive, rod-shaped bacterium and is commonly used as a probiotic to maintain intestinal health. Recently, surveillance of Lactobacillus bacteremia was conducted using biochemical or conventional PCR assay; however, these assays are unable to quantify the target, and might detect a small number of DNA fragments or yield a false-positive result. In this study, we developed an L. rhamnosus-targeting quantitative PCR assay, which produces accurate and reproducible results based on the specificity of a TaqMan probe targeting the unique 16S rDNA sequence of L. rhamnosus. The assay specifically detected the targeted bacterium, L. rhamnosus, and no non-specific signals were generated under the study conditions. Using genomic DNA from the bacterial cells of L. rhamnosus (10¹ to 10⁶ cells), the cycle threshold value showed a linear trend (R² = 0.9993). This L. rhamnosus-targeting quantitative PCR assay can contribute to advance research into the effects of the organism on microflora, microbial infections, and the host.