Use of atmospheric non-thermal plasma as a disinfectant for objects contaminated with methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is the leading cause of healthcare-associated infections (HAI)1. Infections with methicillin-resistant forms of S. aureus (MRSA) increased about ten-fold in the decade between 1995 and 2005 such that an estimated 278,000 to 368,000 hospitalizations for treatment of this organism now occur annually1;2. This trend is linked to the emergence of the USA300 and USA400 clones of MRSA. Because the scope and seriousness of this problem have increased despite implementation of numerous infection control measures, there is interest in new approaches and technologies. Infection control for prevention of MRSA HAIs is typically a layered approach encompassing surveillance, handwashing, barrier precautions, and disinfection of contaminated surfaces and objects3. Transmission of MRSA from health-care workers to patients is generally considered to occur via contamination of the hands; good hand hygiene practices are considered the cornerstone of any infection control program. Weaker evidence suggests that bacterial contamination of objects in the environment plays a role in transmission, probably through an indirect mechanism by contributing to colonization of health-care workers4. Disinfection of potentially contaminated surfaces and objects is recommended to reduce this potential risk5. Few studies have been done linking contamination of inanimate objects carried by or worn on the health-care worker to nosocomial transmission. Concern over the role of clothing including neck ties6 in nosocomial transmission has led to calls for changes in dress code for health-care workers7. The potential for involvement of other commonly carried items, such as hospital badges, beepers, and cell phones, has received relatively little attention8. Most sterilization and disinfection techniques involve exposure to chemical compounds or intense heat for prolonged periods of time5. These treatments are not ideal for a number of potential vectors of transmission because of potential damage to the objects being treated (e.g., electronics, health-care workers’ hands) and are impractical for casual treatment of common items. Recently, increased interest in alternative methods of disinfection and sterilization has led to development of techniques using exposure to plasmas to kill bacteria, viruses and bacterial spores9. Plasmas are generated by inducing gases to enter an ionized state10;11. These plasmas contain short-lived active oxygen species such as ozone, hydroxyl, superoxide, and nitrogen oxides which can have antimicrobial effects. Because plasmas can be generated by application of an electric current at atmospheric pressure and at room temperature, they are being increasingly considered for disinfection or inactivation of bacteria in situations where typical sterilization techniques would cause damage such as with fresh produce12;13. This technique has been shown to be active against a number of gram-negative and gram-positive organisms including biofilm forming agents9;12–14. We conducted the current study to determine whether sterilization of S. aureus including clinically relevant MRSA strains was possible using an atmospheric non-thermal plasma discharge apparatus. Furthermore, we tested its efficacy at disinfecting common hospital items such as beepers which might become contaminated with MRSA.