Microbicidal activity of MDI-P against Candida albicans, Staphylococcus aureus, Pseudomonas aeruginosa, and Legionella pneumophila

Background: MDI-P (Medical Discoveries, Inc–Pharmaceutical, Layton, Utah) is a clear, colorless liquid generated by electrolysis of preservative-free and endotoxin-free, nonpyrogenic, sterile, injection saline (0.9% NaCl, wt/vol). It contains numerous highly reactive chlorine and oxygen species, including HOCl–1, OCl–1, Cl–1, Cl2, O2–1, and O3. This report presents data on the in vitro microbicidal activity of MDI-P against 4 clinically relevant microbial pathogens that are often difficult to eradicate. Methods: MDI-P was generated from injection saline by using a patented electrolysis instrument. It was then tested for microbicidal activity at concentrations ranging from 0.01% to 50% against Staphylococcus aureus, Pseudomonas aeruginosa, Legionella pneumophila, and Candida albicans (105 to 109 colony-forming units/mL). The effect of serum (50% and 90%) and pH on MDI-P activity were also tested. The morphologic effects of MDI-P on microbial cells were studied by light microscopy of cells stained by Gramʹs method and by transmission electron microscopy. Morbidity, mortality, and the effect of MDI-P on tissues were studied by using a mouse model. Results: The microbicidal activity of MDI-P occurred within the first minute of exposure for all the organisms tested. When 50% MDI-P was tested against cell titers of 105 or 107 colony-forming units/mL, all test organisms were killed within 1 minute; at lower MDI-P concentrations, C albicans was the most sensitive organism, and L pneumophila was the most resistant. Even with beginning cell titers of 109 colony-forming units/mL, killing by 50% MDI-P was >99.9% for all test strains. Furthermore, at the same beginning cell titer, killing of C albicans by MDI-P diluted to 50% with normal human serum rather than injection saline was only slightly reduced. No acute morbidity, mortality, or tissue damage was detected in mice that were intravenously given 17 mL/kg of undiluted MDI-P. Conclusions: MDI-P is a very fast-acting, broad-spectrum microbicidal material. The lack of evidence for acute morbidity, mortality, or tissue injury, ease of preparation, and low cost suggest that it may be useful for various sterilization and disinfection applications. (AJIC Am J Infect Control 2000;28:251-7)