Lysosomes identified as key mechanism for clearing hidden bladder bacteria with existing therapy

Urinary tract infections represent a pervasive public health challenge affecting millions of individuals across the globe. While these infections are often considered common, they carry significant morbidity, particularly when they become recurrent. The primary culprit behind the majority of these infections is the uropathogenic strain of Escherichia coli, or UPEC. Unlike typical foodborne strains, UPEC has evolved specific mechanisms to adhere to and invade the lining of the urinary tract. Once inside the bladder, these bacteria can breach the epithelial barrier and establish an intracellular reservoir. This hidden state allows the bacteria to evade both the host immune system and the reach of standard antibiotic therapies. Consequently, patients frequently experience a relapse of symptoms even after completing a course of antibiotics. This cycle of infection and treatment can contribute to the development of antibiotic resistance, a growing concern in modern medicine. To address this, researchers have sought to understand how the host environment can be reinforced to prevent these persistent reservoirs.

A recent study led by scientists at the Laboratory of Microbiology and Microtechnology at EPFL, in collaboration with OM Pharma, has illuminated a potential new pathway for treating these stubborn infections. The research team, which included Kathrin Tomasek, John McKinney, Christian Pasquali, and Mario Romani, focused their efforts on a drug known as OM-89. This compound, commercially marketed as Uro-Vaxom, has been utilized for several decades specifically to assist in the prevention of recurrent urinary tract infections. Traditionally, the mechanism of OM-89 was attributed to immunostimulation, where the drug is thought to activate the immune system. However, this study published in PLOS Pathogens uncovers a distinct mechanism of action. The findings suggest that the drug acts directly on the bladder epithelial cells, influencing their internal machinery to destroy hidden bacteria more effectively.

The cellular mechanisms at play in this study center on lysosomes, which are specialized organelles within cells responsible for degradation and recycling. These acidic compartments function as the cell's digestive system, breaking down unwanted materials and foreign pathogens. The researchers observed that treatment with OM-89 significantly increased the acidification of these lysosomes and enhanced the activity of their enzymatic components. This activation is critical for the clearance of intracellular material. To confirm this mechanism, the team utilized organoid models and differentiated cell cultures derived from both mouse and human bladder tissue. They exposed these cell models to OM-89 and then infected them with various strains of UPEC. The results demonstrated that the bacteria were more efficiently eliminated when lysosomal activity was heightened. Furthermore, when the researchers artificially blocked the acidification of lysosomes, the protective effect of OM-89 was lost. This control experiment confirmed that lysosomal activation is a direct requirement for the drug's ability to reduce bacterial regrowth.