“ Preservation and Probiotic Properties of a freeze-dried mixture of microorganisms isolated from kefir

BOLLA P; MARÍA DE LOS ANGELES SERRADELL

Tucuman

Congreso; III Simposio Internacional de Bacterias Lácticas (BAL).; 2009

CERELA

Probiotic bacteria, mainly lactic acid bacteria (LAB) and yeast, have shown to have beneficial effects on immunomodulation and in the alleviation or prevention of diverse intestinal disorders. Probiotic bacteria are reported to prevent the adherence, establishment and invasion of specific enteropathogens. Ability to temporarily colonize the intestinal epithelia has been linked with probiotic properties because it will allow probiótica bacteria to exert their beneficial effects longer. Several health promoting properties are reported to be associated with kefir consumption. Beneficial effect of kefir can also be attributed to the inhibition of pathogenic microorganims by metabolic products, such as organic acids, secreted by the LAB included in the kefir grain. Taking into account the ability of probiotic bacteria and yeasts isolated from kefir against intestinal pathogens, it is proposed to test this ability by using a mixed formula against Shigella flexneri and Shigella sonnei. To analyze the protective effect on Shigella invasion of Hep-2 cells we preincubated for one hour Hep-2 cells with a mixture culture containing Lactobacillus plantarum (CIDCA 83114), Lactobacillus Kefir (CIDCA 8348) and Lactococcus lactis subsp. lactis (CIDCA 8221) at concentrations of 109 cfu/ml and Kluyveromyces marxianus (CIDCA 8154) and Saccharomyces serevisiae (CIDCA 8112) at concentrations of 106 cfu/ml. This incubation was performed under conditions suitable for cell growth. After washing a clinical isolate of S. sonnei or S. flexneri, alternately, was added with the objective to test their ability of invade Hep-2 cells. This was carried out by the antibiotic protection assay. In addition electron microscopy was performed to assess the physical interactions that occur between the BAL and the yeast with the cells, taking into account these as a possible mechanism to prevent bacterial invasion. We were able to observe a decrease of two orders in the invasive capacity of S. sonnei, whereas in the case of S. flexneri we found a decrease to values below the detection limit of the method, which involves a diminution greater than 4 logs. The electron microscopy showed the existence of a particular structure of the mixed culture where the yeasts are central while the lactoccocus bind closely to them, unlike the lactobacilus that it is at a particular distance. In this microscopy we could also observed the cell damage when Shigella isolates are present (control) unlike to what happens when the mixture culture is present. In conclusion we observed that the mixture culture had a protective role against Shigella invasion, being more important for S. flexneri isolate. This protective effect could be originated by the physical arrangement BAL and yeast over the cells.