Propriedades probióticas de Lactobacillus spp. de origem humana e interação com leveduras potencialmente patogênicas do gênero Candida

Abstract

The dysbiosis, imbalance of the intestinal microbiota, becomes an increasingly common problem nowadays, resulting in various diseases. Consumption of foods enriched with prebiotics and probiotics can promote the proper functioning of the gastrointestinal tract, particularly regarding to competitive exclusion of pathogens and immune system stimulation. Auto-aggregation has been correlated with adherence, a precondition for colonization and infection of the intestinal tract. The probiotics' ability of coaggregation and therefore the competitive exclusion of pathogen are important in modulating the gut microbiota for maintaining health. The aim of this research was study mechanisms which Lactobacillus spp uses to colonize the intestine and interact with potentially pathogenic yeasts of the genus Candida. Tests were conducted to verify if lactobacilli have the ability to aggregate their own cells and yeast cells. Subsequently, we evaluated the affinity to hydrocarbons and inhibition capacity against yeast. The isolates Lac 2 and Lac 4 - both identified as L. paracasei spp. paracasei - and the standard culture L. acidophilus LA-5 showed high rates of auto-aggregation and coaggregation (p <0.05) when compared to other cultures (Lac 1, Lac 3 – both identified as L. rhamnosus - and commercial culture L. casei-01), indicating the existence of correlation between these two variables. Hydrophobicity's test did not show the same correlation, because only Lac 2 and LA-5 results were considerably high. Growth inhibition of Candida albicans by co-cultivation in liquid medium was got with a mean reduction of about 2 log: Lac 1 and Lac 3 showed the best results. Finally, plate inhibition of yeast using cell-free filtrates of lactobacilli was not obtained by any of the cultures; likewise, in auto-aggregation test using filtrates was not observed any significant effect (p <0,05). It is concluded that the characteristics analyzed are due to different factors and they are species-specific or restricted to lower taxonomic levels. For our cultures, the adhesion mechanisms are probably related to molecules present on the cell surface, with no important production of extracellular substances. More detailed studies are needed to elucidate the mechanisms involved in competitive exclusion of pathogens. Beneficial bacteria isolated from human origin have great potential for use as probiotics.