Dimova M. Bacteriocinogenic and probiotic properties of lactobacilli

The screening of strains with bacteriocinogenic activity was conducted among 67 cultures of lactic acid bacteria. The strain L.plantarum UCM B-2705 was selected. The native and concentrated antibacterial substance of the strain was active against lactobacilli, and also against clinical important, opportunistic microorganisms, such as Enterococcus faecalis, E. faecium, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Salmonella enterica. The antagonistic factor was a thermolabile protein with the molecular weight more than 10 kDa, active at pH 2,0-8,0, and not plasmid-encoded. The obtained results allow to attribute the antagonistic substance to the group II or III, but not to the group IV (complex bacteriocins) and not to the group I (peptids smaller than 5 kDa) according to classification of lactic acid bacteria bacteriocins. The beginning of the bacteriocin-like substance production into the medium was during the exponential growth phase of the strain-producer, the peak of the activity ofthis factor - in the stationary growth phase. The producer strain was tested according to the basic requirements to probiotic strains by WHO. The strain has been identified as Lactobacillus plantarum by genetic methods. The susceptibility test to 57 antibiotics of different groups and with different mechanisms of action showed that the strain was resistant to 32 antibiotics, among them - to aminoglycosides, fluoroquinolones, antifungal ones, some penicillins, cephalosporins, fusidine, vancomycin, polymyxin.The strain has been shown to be highly adhesive to the human epithelial cells and contain glycolipid adhesins. The perspective use of the strain L.plantarum UCM B-2705 as a component of probiotics due to its antagonistic and adhesive properties has been established.