It is common for environmental surfaces to become soiled with blood, saliva, exudate, and other biological matter in health care settings during patient care. It is also well documented that environmental contamination can play an important role in the transmission of health care-associated infections in hospitals and long-term care facilities.1,2 Causative pathogens include Staphylococcus aureus, noroviruses, Clostridium difficile, and hepatitis C virus. Other microbial etiologies include a variety of bacterial, viral, and fungal nosocomial pathogens, including isolates that have become increasingly drug resistant.3,4
Even before the COVID-19 pandemic, investigations determined that most gram-positive bacteria, many gram-negative bacteria, blood-borne viruses (for example, hepatitis B and hepatitis C viruses), and a number of respiratory tract viral pathogens were able to survive on inanimate surfaces for days, weeks, or longer (Table 12,5-8,10). Persistent organisms, such as methicillin- resistant S. aureus, also can be frequently passed to inanimate items from contaminated health care professionals’ (HCP) hands and gloves. Methicillin-resistant S. aureus and other organisms can be difficult to eliminate if recommended cleaning and disinfection procedures are not followed. Findings from a 2020 study showing that viable severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus can be detected for hours to a few days on inanimate surfaces have further increased cross infection concerns for medical and dental HCP and the public.8
Ongoing research and clinical reports studying surface cross- contamination and cross-infection risks have provided HCP with science-based principles, protocols, and practices. Compliance with basic tenets and their applications is fundamental in health care facilities, and environmental surface asepsis between patients remains an important component of an effective infection
prevention program. The following brief discussion will focus on dental settings by outlining current guidance from appropriate governmental and health professional agencies. Key principles and elements of a successful surface asepsis program in dental practices will be discussed.
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Selection of a Surface Disinfectant
There were far fewer products available for dental practices in the 1980s and 1990s in comparison with the wide array of current surface disinfectant sprays and wipes that offer a range of antimicrobial and use characteristics. Unfortunately, selection of a product can be difficult owing to exaggerated claims, misleading reports in the literature, or lack of awareness about the appropriate guidelines to follow. These issues can be prevented by comparing the efficacy of available agents with their published properties for an ideal surface disinfectant (Table 2 9,10). Although the perfect surface disinfectant has not been found, dental practices can make more informed choices by using the following criteria when evaluating disinfectant candidates.
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Classification of Chemical Disinfectants and Sterilants
Chemical disinfectants in the United States are regulated and registered with the Environmental Protection Agency (EPA), while chemical sterilants and high-level disinfectants are regulated by the US Food and Drug Administration. Major distinctions between the 3 chemical categories as classified by the Centers for Disease Control and Prevention are shown in Figure 1.11
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1. Low-level: EPA-registered as a hospital disinfectant.
These are chemicals with the narrowest antimicrobial range and are termed hospital-level disinfectants. To receive EPA approval, they are required to show effectiveness against 3 species of test pathogens: S. aureus, Salmonella choleraesuis, and Pseudomonas aeruginosa. The Occupational Safety and Health Administration requires low-level disinfectants to also have a label claim for effectiveness against hepatitis B virus and HIV if used for disinfecting clinical contact surfaces. Low-level disinfection is a process that will inactivate most vegetative bacteria, some fungi, and some viruses, but it cannot be relied on to inactivate resistant microorganisms such as mycobacteria.
2. Intermediate-level: EPA-registered as a hospital disinfectant with a tuberculocidal claim.
Although they do not inactivate bacterial endospores, intermediate-level disinfectants kill many other microbial forms, including tubercle bacteria (that is, Mycobacterium tuberculosis). M. tuberculosis presents a severe challenge to disinfectants and is routinely used as a test organism owing to its resistance. Documented tuberculocidal activity assures the user that the product is an intermediate-or high-level disinfectant and that it will kill microorganisms known to be potential pathogens in dentistry.
3. High-level: US Food and Drug Administration–approved chemical agents capable of sterilizing items, but only after prolonged immersion intervals (that is, glutaraldehydes, hydrogen peroxide, and peracetic acid). Treatment of contaminated environmental surfaces does not require use of chemical sterilants or high-level disinfection and will not be discussed further.
When reviewing the examples of microbes in Figure 1, it becomes apparent that coronaviruses are a group of viruses that are susceptible to disinfection. One of the features used to characterize viruses is the presence or absence of a lipid envelope. Enveloped (hydrophobic) and nonenveloped (hydrophilic) viruses have different susceptibilities to chemical disinfectants. Hydrophobic viruses are much more susceptible to these chemical preparations than hydrophilic ones. This was shown to be due to the presence of essential lipids in the viral envelope. Coronaviruses including SARS-CoV-2 are enveloped viruses. Concerns about the effectiveness of different disinfectants against SARS-CoV-2 led the EPA to develop a list (List N) of disinfectants for use against SARS-CoV-2.12 All products on the list must meet EPA criteria for use against SARS-CoV-2, and the list is routinely updated. Most dental facilities routinely use intermediate-level surface disinfectants; they require higher EPA kill standards than the low-level agents. Thus, there are many available products that are effective against SARS-CoV-2. Check EPA List N to confirm that your practice’s disinfectants are included.
Environmental Surface Asepsis Checklist for Dental Practice
Figure 2 provides a suggested protocol for environmental surface asepsis in dental facilities. It was developed as a component of a comprehensive infection control resource by the Organization for Safety, Asepsis, and Prevention in conjunction with DentaQuest.13 It is advisable to consult the complete document as infection control practices and protocols will be updated during and after COVID-19. Dental professionals may also want to consult a checklist published in July 2020, which provides additional useful supplemental information.14
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About the author
Dr. Molinari earned a PhD in microbiology from the University of Pittsburgh and subsequently worked as a faculty member in the School of Dental Medicine. He is a Professor Emeritus at the University of Detroit Mercy, where he served for 32 years in the School of Dentistry as Professor and the chairman of the Department of Biomedical Sciences and the director of Infection Control. Later, he was the infection control director for Dental Advisor where he was involved in research on newly developed infection prevention technologies and products. He has published more than 500 scientific articles, text chapters, and abstracts in the areas of microbiology and immunology, and he lectures nationally and internationally on topics dealing with infectious diseases and infection control. He also has been a consultant for the Centers for Disease Control and Prevention, the American Dental Association, and regional hospitals.
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