The principal goal of this current study was to isolate a new potential probiotic strain to prepare contamination-free probiotic dahi in a dosage form with desired shelf life. To achieve our target, firstly, probiotic dahi was prepared by a probiotic strain, Lactobacillus acidophilus JB2CON (OM909067) (identified by 16S sequencing) isolated from natural dahi in Dhaka, Bangladesh. The isolate showed five probiotic features by in vitro test and had an antagonistic effect against five different pathogens. More interestingly, it inhibited Escherichia coli (diameter of zone of inhibition = 15.75±0.35) the most. In the time-kill analysis method, E. coli was killed totally within 5.50 hours of fermentation. Finally, the time duration of 14 days was an ideal shelf life, because the probiotic count increased but a slight change in pH did not affect the taste (sourness/acidity) of dahi. The most significant impact of this research is that the probiotic dahi of our experiment might be used as a cheap option for preventing pathogenic Escherichia coli-related foodborne diseases worldwide, especially in underdeveloped countries like Bangladesh.