Evaluation of Bactericidal Effect of Electric Devices Advertising the Ability to Kill Environmental Bacteria

Abstract

  Several electric devices are sold in the market by famous electric companies in Japan which are advertised to have effective properties for inactivating airborne viruses and bacteria. If such claims were realistic and reliable, these devices would be useful for infection control in many settings. However, no scientific reports which passed the process of impartial and strict peer review have investigated such claims. Therefore, we tried to evaluate the bactericidal effects of some devices. The devices examined were the “Plasmacluster ioniser” of Sharp Co, Japan, “Nano-e generator”of Panasonic Co, Japan, and “Eneloop Air-fresher” of Sanyo Co, Japan. Bactericidal effects were tested using S. aureus, P. aeruginosa, B. cereus, and E. faecalis as follows: two small droplets of 1 μL each, containing a certain amount of each bacterium were put onto a glass slide and smeared. The slides were kept in a closed glove box of 0.2 m³ inner volume, and one of the devices was operated in the box for a given length of time. Glass slides not exposed to any device were used as controls. Each glass slide was retrieved from the box and the smear on the slide was washed out with 1 mL of culture medium. The medium was collected and the amount of living bacterium was titrated by the pour-plate-culture method. There was no significant difference in the amount of bacteria from the slides exposed with the devices compared with the controls, for all bacteria tested and all devices examined. These results strongly suggest that such devices have almost no bactericidal effect, at least on the bacteria under the conditions used in the study.