Lactobacillus K7 - A new candidate for a probiotic strain

Lactobacillus K7 is an isolate from faeces of week-old breast-fed baby that has been previously found to exhibit bacteriocin-like activity against var ious species of lactic acid bacteria and Clostridium sp. In this study part ial identification of the strain K7 was done and some basic probiotic prope rties such as resistance to low pH, bile and bacteriocin production were in vestigated. The effect of bacteriocin of the strain K7 against C. perfringe ns and C. difficile vegetative cells and against C. tyrobutyricum vegetativ e cells and spores was also examined. On the basis of morphological charact eristics, API 50 CHL (BioMerieux) fermentation pattern and analysis of S-la yer, the strain K7 was identified as a member of L. acidophilus DNA homolog y group B. 43 % of the K7 strain cells survived 3 h in the presence of 0.3 % w/v bile. The viable count during 3 h incubation at pH=3 was reduced by 5 1 %. Bacteriocin was produced at highest values during the exponential phas e of growth. Maximal activity in the supernatant of MRS culture (32 000 AU/ mL) was detected after 8 h of cultivation. Minimal inhibitory concentration s (MIC) of bacteriocin of the strain K7 for C. tyrobutyricum vegetative cel ls were 640-2560 AU/mL, depending on the strain tested, and 1280 AU/mL for all C. difficile and C. perfringens strains. The sensitivity of the C. tyro butyricum spores was higher than of vegetative cells and MIC varied between bacterial strains as well (1280-->5120 AU/mL).