Características probióticas de linhagens de Lactobacillus isoladas da mucosa gástrica de suínos

Abstract

The genus Lactobacillus is part of the normal microbiota of the digestive tract of swine, including the stomach. Bacteria that colonize this region are considered a source of Lactobacillus to more distal portions of the digestive tract, by the continual desquamation of the stomach epithelium and may contribute to the regulation of the composition of the intestinal microbiota. Bacteria that colonize this region are still poorly studied and may have probiotic potential. This work aimed at the probiotic characterization of 19 strains of Lactobacillus isolated from gastric mucosa of pigs that were identified in a previous study. The probiotic characteristics evaluated were tolerance to the gastric juice and bile salts, cell surface hydrophobicity, biofilm production, gastric mucin degradation, antibiotic resistance and in vitro antagonism against Salmonella enterica serovar Typhimurium, Listeria monocytogens, Staphylococcus aureus, Enterococcus faecalis, Bacillus cereus, Klebsiella pneumoniae, Acinetobacter baumannii and Klebsiella pneumoniae Carbapenemase. All 19 strains exhibited resistance to gastric juice, of which 11 had 0% inhibition of growth at pH 2.5. Only one strain was resistant to bile salts at 0.3%, being most of them (58%) tolerant. Regarding the cell surface, 57% of the strains were hydrophobic and 31% were moderately hydrophobic. All strains were able to form biofilm, 74% of which were strong producers and 26% were moderate biofilm producers. None of the strains tested exhibited mucin degradation halos, except for the positive controls - Salmonella Typhimurium and Shigella flexneri. In the antagonism assay, a strain of Lactobacillus (Lac6) stood out from the others, showing antagonistic activity against all pathogens tested, while most strains (63%) antagonized at least 3 pathogens. In the antibiogram test, strains that grew in aerobic atmosphere were resistant to a considerable number of antibiotics, results that point to the need of investigating the genetic nature of these resistances. Our results showed that Lactobacillus strains isolated from healthy gastric mucosa of pigs have different profiles of in vitro probiotic characteristics that deserve to be explored. In particular, the strain Lac6, due to its greater spectrum of antagonism, in addition to the other characteristics evaluated, would be the strain of choice for the characterization of in vivo probiotic activity, however, because the strain showed resistance to several antibiotics, it would be important to evaluate the source of this resistance.