Assessment of the Persistence in the Human Intestinal Tract of Two Probiotic Lactobacilli Lactobacillus salivarius I 1794 and Lactobacillus paracasei I 1688

Abstract

A major concern in studies of probiotic bacteria is the assessment of their persistence in the human intestinal tract. The problem of a positive identification of the introduced strains has been recently addressed by means of molecular biological techniques. However, up to now, only probiotic products containing a single strain have been investigated by means of genetic identification tools. In this study, the presence in the faecal flora of ten healthy volunteers of two recently characterised probiotic strains, Lactobacillus salivarius I 1794 and Lactobacillus paracasei I 1688, was monitored before, during, and after the administration of a dietetic product containing both strains (daily dose 1 &#50 10 9 CFU). The overall duration of the study was 21 days and it was divided into three parts: a 7 days control period (abstention from products containing Lactic Acid Bacteria (LAB)), a 7 days treatment period (administration of 1 sachet per day of a product containing a mixture of the two strains), and a further 7 days, post-treatment period. Throughout the study, the volunteers did not take any products (food/drugs/dietetics) claimed to contain probiotic lactobacilli. Faecal samples were analysed by plate counting at the end of each period. RAPD-PCR identification of L. salivarius I 1794 and L. paracasei I 1688 was performed on a significant number of CFU grown on Rogosa acetate agar medium. Eight out of ten treated volunteers showed the presence with at least one of the studied strains after a week of treatment and two out of six volunteers after a week from discontinuation of the consumption of lactobacilli. Among the volunteers in which the presence was demonstrated at the end of the 7 days of administration, three showed the presence of L. salivarius I 1784 only, one showed L. paracasei I 1688 only and four showed both strains, while at the end of the 7 days of post-treatment, one showed the persistence of L. salivarius I 1784 only and one showed L. paracasei I 1688 only. We concluded that the treatment regimen used in this study, with a 7 day consumption of a product containing L. salivarius I 1794 and L. paracasei I 1688, allows these bacteria to establish themselves, flourish and persist, at least transiently, in the human intestinal tract.

• Lactobacilli
• Persistence
• Pcr Identification
• Probiotics