Abstract
Probiotic strains have different profiles regarding adhesion capacity, antimicrobial activity and, possibly, clinical effects. Among probiotics, certain Lactobacillus strains have been studied most intensively. However, positive effects have been studied and proven for only a few specific strains. By in vitro experiments we have identified five Lactobacillus strains with promising results regarding adhesion and antimicrobial effects. In the current study their gastrointestinal effects, mucosal colonisation and safety in healthy adults was evaluated. Patients and design and main outcome measures: Thirteen men (median age 25 years) received three preparations each for 18 days with a 17 day wash-out between periods: Preparation A, a mixture of two new strains ( Lactobacillus rhamnosus 19070-2, and L. reuteri DSM 12246); Preparation B, a mixture of three commercially used strains, L. casei subsp. alactus CHCC 3137, L. delbrueckii subsp. lactis CH 2329, and L. rhamnosus GG. Preparation C contained placebo. Gastrointestinal transit time was measured using radio opaque markers, blood lipids were measured before and after each intervention, and stool was sampled to culture for the aerobic and anaerobic flora and for identification of the test strains by Restriction Enzyme Analysis combined with Pulsed Field Gel Electrophoresis (REA-PFGE). Results : All three preparations were well tolerated and did not interfere with the frequency of bowel movements, gastrointestinal transit time or serum lipid levels. Administration of preparation A significantly decreased the counts of Staphylococcus aureus (median 4.7 (range 0-8.8) log versus median 3.2 (range 0-4.6) log ( p =0.046)) while other species were not affected. Preparation B had no effect on the gastrointestinal flora. After 10 days ingestion of preparation A the test strains were identified from colonic biopsies in 10/11 volunteers, mainly from the ascending and transverse colon. Conclusions: A direct link from in vitro experiments to in vivo evaluation was established. The test preparations were well tolerated. Persistence and adhesion in the gastrointestinal tract was confirmed in vivo by faecal recovery and detection in colonic biopsies.