Integrated probiotic fitness screening reveals dose-sensitive immunomodulatory profiles of indigenous lactic acid bacteria
TL;DR
Findings support the concept that probiotic potential is a structured, strain-specific and dose-depencent phenotype rather than a single screening trait.
Abstract
Indigenous lactic acid bacteria (LAB) are under-characterized reservoirs of probiotic candidates, but many screening studies do not connect gastrointestinal fitness with host epithelial immune response. This study analyzed 20 LAB isolates from Indonesian local sources, including wild horse milk, whey, infant feces, yogurt and soil samples. Isolates were evaluated for survival at pH 2.5, tolerance to 1% and 5% oxgall, antagonism against Escherichia coli , Staphylococcus aureus and Bacillus cereus , adhesion to stainless steel and modulation of interleukin-8 (IL-8) secretion in HCT116 colon epithelial cells. Probiotic fitness was strongly strained. Sixteen isolates survived acidic exposure, all isolates tolerated bile and pathogen inhibition differed by target organism. Integrated prioritization identified SK3, WT1, WT2, SK2 and FS1 for adhesion testing. WT1 showed the highest adhesion (4.9 log cells/cm 2 ), whereas SK3 combined relatively strong acid tolerance with broad pathogen antagonism. In HCT116 co-culture, SK3 and WT1 reduced IL-8 levels at bacteriral concentrations of 10 7 -10 8 CFU/ml compared with the epithelial-cell control (24.58 pg/ml), but increased IL-8 at 10 9 CFU/ml (36.60 and 35.25 pg/ml, respectively). These findings support the concept that probiotic potential is a structured, strain-specific and dose-depencent phenotype rather than a single screening trait.