New mechanistic data suggest OM-89, long used to help prevent recurrent UTIs, protects by acting directly on bladder epithelial cells rather than only via immune stimulation. Research published in PLOS Pathogens reports that OM-89 increases lysosomal acidification and lysosomal enzyme activity, improving clearance of intracellular uropathogenic E. coli. In organoid models and differentiated human bladder epithelial cultures, OM-89 enhanced antibiotic uptake into bladder cells, extending across antibiotic classes and E. coli strains, including clinical isolates. Blocking lysosomal acidification removed the protective effect, strengthening the causal link. Clinicians may interpret the findings as a rationale to revisit how preventative therapies are positioned alongside antibiotic strategies for recurrent infections—especially when intracellular bacterial reservoirs drive relapse.