Cold atmospheric pressure plasma and decontamination. Can it contribute to preventing hospital-acquired infections?

Healthcare-associated infections (HCAIs) affect ∼4.5 million patients in Europe alone annually. With the ever-increasing number of 'multi-resistant' micro-organisms, alternative and more effective methods of environmental decontamination are being sought as an important component of infection prevention and control. One of these is the use of cold atmospheric pressure plasma (CAPP) systems with clinical applications in healthcare facilities. CAPPs have been shown to demonstrate antimicrobial, antifungal and antiviral properties and have been adopted for other uses in clinical medicine over the past decade. CAPPs vary in their physical and chemical nature depending on the plasma-generating mechanism (e.g. plasma jet, dielectric barrier discharge, etc.). CAPP systems produce a 'cocktail' of species including positive and negative ions, reactive atoms and molecules (e.g. atomic oxygen, ozone, superoxide and oxides of nitrogen), intense electric fields, and ultraviolet radiation (UV). The effects of these ions have been studied on micro-organisms, skin, blood, and DNA; thus, a range of possible applications of CAPPs has been identified, including surface decontamination, wound healing, biofilm removal, and even cancer therapy. Here we evaluate plasma devices, their applications, mode of action and their potential role specifically in combating HCAIs on clinical surfaces.

The antimicrobial effects of helium and helium-air plasma on Staphylococcus aureus and Clostridium difficile.

UNLABELLED: Healthcare-associated infections (HCAI) affect 5-10% of acute hospital admissions. Environmental decontamination is an important component of all strategies to prevent HCAI as many bacterial causes survive and persist in the environment, which serve as ongoing reservoirs of infection. Current approaches such as cleaning with detergents and the use of chemical disinfectant are suboptimal. We assessed the efficacy of helium and helium-air plasma in killing Staphylococcus aureus and Clostridium difficile on a glass surface and studied the impact on bacterial cells using atomic force microscopy (AFM). Both plasma types exhibited bactericidal effects on Staph. aureus (log3·6 - >log7), with increased activity against methicillin-resistant strains, but had a negligible effect on Cl. difficile spores (<1log). AFM demonstrated cell surface disruption. The addition of air increased the microbicidal activity of the plasma and decreased the exposure time required for an equivalent log reduction. Further evaluation of cold plasma systems is warranted with, for example, different bacteria and on surfaces more reminiscent of the health care environment as this approach has potential as an effective decontaminant. SIGNIFICANCE AND IMPACT OF THE STUDY: Many bacterial causes of healthcare infection can survive in the inanimate environment for lengthy periods and be transmitted to patients. Furthermore, current methods of environmental decontamination such as detergents, chemical disinfectants or gaseous fumigation are suboptimal for a variety of reasons. We assessed the efficacy of helium and helium-air plasma as a decontaminant and demonstrated a significant reduction in bacterial counts of Staphylococcus aureus on a glass surface. Atomic force microscopy morphologically confirmed the impact on bacterial cells. This approach warrants further study as an alternative to current options for hospital hygiene.

Microbial monitoring of the hospital environment: why and how?

BACKGROUND: The purpose of microbial monitoring of the inanimate environment surrounding a patient can be two-fold; to monitor hygiene standards and also to examine for the presence of specific nosocomial pathogens which may be the source of an outbreak. While both purposes involve routine culture of microorganisms, the methods used for each can differ in order to provide optimal results. The main difference between both purposes is the need for enumeration, site specificity for an aerobic colony count (ACC) for hygiene assessments, and the need to simply detect the presence or absence of multi-resistant nosocomial pathogens for infection control surveillance. AIM: To access current methods used in research studies and during outbreak investigations to detect nosocomial pathogens in the inanimate environment in the clinical setting. METHODS: A Pubmed search of published literature was performed. FINDINGS: Microbial monitoring of the environment can involve the use of swabs, sponges, contact plates and dip slides coupled with a variety of enrichment broths and selective media. The use of molecular methods such as polymerase chain reaction (PCR) can potentially provide a faster turnaround time, resulting in the quicker implementation of infection prevention and control cleaning and disinfection regimens. However, the optimal methods for performing a microbial hygiene evaluation or detecting specific bacterial pathogens are not generally agreed. CONCLUSION: There is a need for agreed standards on the optimal methods, frequency of environmental sampling and acceptable levels of surface contamination within the healthcare system.