RELATEDNESS OF LACTOBACILLUS-RHAMNOSUS STRAINS ISOLATED FROM CLINICALSPECIMENS AND SUCH FROM FOODSTUFFS, HUMANS AND TECHNOLOGY

Four hundred and fifty-nine samples of food-stuffs nonindustrial start er cultures and feces from pigs, cows and healthy humans were screened for the presence of Lactobacillus rhamnosus, and in total 45 strains were isolated. Lactobacillus rhamnosus was frequently found in human f eces (39.9%), hard cheese (27.3%) and soft cheese from raw milk (25%) but rarely in raw-milk pools (1.6%) and not at all in feces from cows and pigs. These results suggest that humans are one major reservoir fo r L. rhamnosus The isolated strains and jive others from infected pers ons and three used in milk technology were analysed for the presence o f macrocapsules, haemolysins, haemagglutination, serum resistance and plasmid DNA. Both macrocapsules and haemagglutination were only demons trated for one strain each. Antibiogram and plasmid fingerprinting did not discriminate the strains. However, serum resistance testing allow ed a certain discrimination. Three strains (5.7%) were partly inactiva ted, 11 (20.7%) showed a steady state and 39 (73.6%), including all cl inical isolates, were able to grow and were therefore clearly serum re sistant. The high similarity of the examined strains suggest that a ce rtain potential to cause infection is a characteristic inherent to L. rhamnosus and not limited to a cluster of particular strains. This fin ding, the fact that infections due to L. rhamnosus are very rare and o ccur only under certain preconditions and the observation that L. rham nosus is obviously a part of the normal bacterial flora in the human i ntestinal tract, should diminish the scepticism in connection with the technological use of this microorganism. However, it must be recommen ded that L. rhamnosus strains used in fermented or probiotic products are free of macrocapsules, haemagglutination properties, transmissible antibiotic resistances and high level serum resistance.