Vol.73 No.6 November 2025
Impact of high-speed nanodroplet collisions on Pseudomonas aeruginosa cells and biofilm formation
1)Division of Clinical Infectious Diseases & Chemotherapy, Tohoku Medical and Pharmaceutical University, Graduate School of Pharmaceutical Sciences, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi, Japan
2)Institute of Fluid Science, Tohoku University
Abstract
High-speed nanodroplet technology, developed in 2017, is the world's first technique capable of generating and rapidly exposing to groups of nanodroplets miniaturized to less than 100 nm in diameter via water vapor condensation. This study was aimed at evaluating the effectiveness of this novel sterilization method against biofilm-forming Pseudomonas aeruginosa, a particular problem in nosocomial infections. Five multidrug-resistant Pseudomonas aeruginosa (MDRP) strains, clinically isolated from a medical institution in the Tohoku region of Japan, along with the P. aeruginosa PAO1 strain, were used to prepare biofilm formation models. These models were exposed to 100 nm-diameter nanodroplets at an impact pressure of 1.8×108 Pa (18 MPa) for 20-30 minutes. Subsequently, the viable count, amount of biofilm formation, and extracellular matrix (ECM) components were measured. Additionally, morphological changes in the bacteria were examined by scanning electron microscopy (SEM). After 20 minutes of nanodroplet exposure, no significant reduction in the viable count was observed. However, the amounts of polysaccharides and extracellular DNA (eDNA) in the ECM decreased, leading to a reduction in biofilm formation. This suggests that the decrease in polysaccharides and eDNA contributed to weakening of the structure of the biofilm. In contrast, after 30 minutes of exposure, the viable count decreased in all six strains, with MDRP-5 exhibiting a bactericidal effect of over 99.9%. SEM observations revealed pore formation in the PAO1 cells and complete destruction of the cell integrity in the MDRP-5 cells. These results indicate that high-speed nanodroplet technology disrupts the structure of the biofilm and physically kills P. aeruginosa through mechanical impact. The bactericidal effect was greater in strains showing lower biofilm formation, suggesting that biofilm destruction may enhance the bactericidal efficiency. Because this technique uses only water and does not rely on chemical disinfectants, it is effective regardless of bacterial drug susceptibility. In addition, only a small amount of water is used, and it is expected that the number of options for sterilization methods will increase when the method is put to practical use after further studies.
Key word
Pseudomonas aeruginosa, biofilm, nano droplet, extracellular matrix
Received
April 11, 2025
Accepted
July 8, 2025
Jpn. J. Chemother. 73 (6): 563-571, 2025
