Kristin Cunningham

Project title: Disinfection of Pathogens on Environmental Surfaces by Spray Application of a Disinfectant

Degree: MS | Program: Environmental Health (EH) | Project type: Thesis/Dissertation
Completed in: 2005


Pathogenic microorganisms cause a wide-range of infectious diseases through various modes of transmission, such as water, food, person-to-person contact, and inanimate surfaces. Contaminated surfaces may serve as fomitic reservoirs of pathogens according to the organisms' ability to adsorb and persist in the environment. The purpose of this study is to determine the efficacy of disinfection of pathogen-contaminated environmental surfaces using a spray application of Cryocide20™ (R.P. Adam, LTD.), a newly developed commercial disinfected. Two bacteria, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resitant Enterococi (VRE), as well as two viruses, poliovirus (PV), vaccine strain, and feline calicivirus (FCV), were examined. The bacteria are highly infectious pathogens responsible for frequent nosocomial and community-based outbreaks of skin, wound, gastrointestinal, and other infections. The viruses, while posing limited threats to human health presently, serve as appropriate surrogate organisms for other common pathogenic viruses, such as Noroviruses. To determine the germicidal activity of Crycodide20™, which is a liquid solution containing chlorine dioxide (stabilized as chlorite) and a twin-chain quaternary ammonium compound, test organisms were applied to various hard and soft surfaces (glass, stainless steel, floor tile, synthetic carpet, and cotton cloth), allowed to dry, and then exposed to a uniform spray application of disinfectant (test samples) or sterile de-ionized water (controls). After a contact period of one hour, organisms were recovered from surfaces in a neutralizing solution and assayed on the appropriate culture media (bacteria) or by cell culture (viruses). Results showed that, compared to surfaces sprayed with water, disinfection of surfaces sprayed with Cryocide20™ was variable. Inactivation of all organisms on all surfaces ranged from a log10 reduction factor of 0.4 >4.2, with better disinfection results for bacteria than those for viruses. For comparison, disinfectant was applied directly to organisms (bacteria) in liquid suspensions, which resulted in up to >5.4 log10 reduction. The results of this study indicate that Cyrocide20™ may be an effective disinfectant for many microorganisms, although its efficacy depends on target organism, surface type, and disinfectant volume. Overall, this study suggests that spray application of Cyrocide20™, while not quite as effective as direct liquid application, may effectively reduce infectious microorganisms and potential human exposures from contaminated environmental surfaces.