Extracellular matrix stiffness modulates host-bacteria interactions and antibiotic therapy of bacterial internalization.

Pathogenic bacteria evolve multiple strategies to hijack host cells for intracellular survival and persistent infections. Previous studies have revealed the intricate interactions between bacteria and host cells at genetic, biochemical and even single molecular levels. Mechanical interactions and mechanotransduction exert a crucial impact on the behaviors and functions of pathogenic bacteria and host cells, owing to the ubiquitous mechanical microenvironments like extracellular matrix (ECM) stiffness. Nevertheless, it remains unclear whether and how ECM stiffness modulates bacterial infections and the sequential outcome of antibacterial therapy. Here we show that bacteria tend to adhere to and invade epithelial cells located on the regions with relatively high traction forces. ECM stiffness regulates spatial distributions of bacteria during the invasion through arrangements of F-actin cytoskeletons in host cells. Depolymerization of cytoskeletons in the host cells induced by bacterial infection decreases intracellular accumulation of antibiotics, thus preventing the eradication of invaded bacterial pathogens. These findings not only reveal the key regulatory role of ECM stiffness, but suggest that the coordination of cytoskeletons may provide alternative approaches to improve antibiotic therapy against multidrug resistant bacteria in clinic.