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

Background: MDI-P (Medical Discoveries, Inc-Pharmaceutical, Layton, Utah) i s 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, inc luding HOCl-1 OCl-(1), Cl-1, Cl-2, O-2-(1), and O-3. This report presents d ata on the in vitro microbicidal activity of MDI-P against 4 clinically rel evant microbial pathogens that are often difficult to eradicate. Methods: MDI-P was generated from injection saline by using a patented elec trolysis instrument. It was then tested for microbicidal activity at concen trations ranging from 0.01% to 50% against Staphylococcus aureus. Pseudomon as aeruginosa, Legionella pneumophila, and Candida albicans (10(5) to 10(9) 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 Gram's method an d 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 minut e of exposure for all the organisms tested. When 50% MDI-P was tasted again st cell titers of 10(5) or 10(7) colony-forming units/mL, all test organism s were killed within 1 minute; at lower MDI-P concentrations, C. albicans w as the most sensitive organism, and L pneumophila was the most resistant. E ven with beginning cell titers of 10(9) colony-forming units/mL, killing by 50% MDI-P was >99.9% for all test strains. Furthermore, at the same beginn ing cell titer, killing of C albicans by MDI-P diluted to 50% with normal h uman serum rather than injection saline was only slightly reduced. No acute morbidity, mortality. or tissue damage was detected in mice that were intr avenously given 17 mL/kg of undiluted MDI-P. Conclusions: MDI-P is a very fast-acting, broad-spectrum microbicidal mater ial. The lack of evidence for acute morbidity, mortality, or tissue injury, ease of preparation, and low cost suggest that it may be useful for variou s sterilization and disinfection applications.