Single pass inactivation of airborne multidrug resistant bacteria using electron beam irradiation with mechanistic evidence

Airborne and aerosol transmission of multidrug-resistant (MDR) bacteria pose a major challenge in healthcare environments. This study evaluated the performance of an electron-beam irradiation (EBI) system for inactivating airborne MDR bacteria under controlled laboratory conditions. To perform this assessment, clinical isolates of MDR Pseudomonas aeruginosa, Acinetobacter sp., Klebsiella sp., and methicillin-resistant Staphylococcus aureus (MRSA) were aerosolized to simulate realistic airborne transmission and subsequently introduced into the EBI system. Downstream bacterial aerosols were collected using liquid impingers and quantified by culture-based enumeration. CFU data were log₁₀-transformed prior to analysis. The EBI system reduced airborne bacterial loads by 4.01 log₁₀ for P. aeruginosa, 3.64 log₁₀ for Acinetobacter sp., 3.64 log₁₀ for Klebsiella sp., and 5.37 log₁₀ for MRSA, corresponding to disinfection efficiencies of 99.98-99.999%. Scanning electron microscopy (SEM) and elemental mechanistic study revealed morphological damage, including membrane rupture, surface collapse, and loss of structural integrity, suggesting that electron impact and electroporation may be major mechanisms of inactivation. These results demonstrate that EBI is a rapid and effective method for mitigating airborne MDR bacterial threats, with potential for deployment in healthcare, laboratory, and other high-risk indoor environments.