Adhesion Properties of Probiotic <i>Lactobacillus</i> Strains Isolated from Tunisian Sheep and Goat Milk

International audienceFour hundred strains isolated from Tunisian sheep and goat raw milks were initially screened for their ability to survive the GastroIntestinal Tract (GIT). Forty-three among the four hundred bacteria were resistant to pepsin, pH 2, pancreatin and bile salts at 0.3%, even after 5 hours of incubation. Identification using 16S rRNA gene sequencing was established and we obtained as a species Lactobacillus plantarum (29 isolates from sheep milk and 11 from goat milk) and Lactobacillus pentosus (2 isolates from sheep milk and 1 from goat milk). We showed the ability for auto-aggregation and/or hydrophobicity properties. Finally, both M63 and C78 strains showed an important level of adhesion to three intestinal epithelial cells Caco-2 TC7, HT29-MTX, and HT29-CL.16E. Taken together, these properties allow the lactobacilli strains to be considered promising beneficial strains for developing functional foods for consumers

Survival Tests for Leptospira spp.

International audienceMeasuring viability is an important and necessary assessment in studying microorganisms. Several methods can be applied to Leptospira spp, each with advantages and inconveniencies. Here, we describe the traditional colony-forming unit method, together with two other methods based respectively on the reducing capacity of live cells (Alamar Blue Assay) and differential staining of live and dead cells (LIVE/DEAD BacLight). The Alamar Blue Assay uses the blue reagent resazurin, which can be reduced into the pink reagent resorufin by live cell oxidoreductases. Production of resorufin can be quantified by absorbance or fluorescence reading. The LIVE/DEAD BacLight assay uses a mixture of two nucleic acid dyes (Syto9 and propidium iodide) that differentially penetrate and stain nucleic acid of cells with decreased membrane integrity. The colony-forming unit method is labor-intensive but the most sensitive and linear method. The two other methods are not laborious and well-adapted to high throughput studies but the range of detection and linearity is limited