Fomite or environmental surfaces can be conveniently divided into two major categories: (1) clinical contact surfaces such as dental units, x-ray machines, equipment knobs and controls; and (2) housekeeping surfaces.1,2 Housekeeping surfaces can be further subdivided into (1) those with frequent hand contact such as doorknobs, light switches, walls around toilets; and (2) those with minimal hand contact such as floors, ceilings, window sills, blinds, and curtains.1,2
Strategies for cleaning and disinfecting environmental surfaces take into account (1) the potential for direct patient contact; (2) the degree and frequency of hand contact; and (3) the likelihood that the surface will be contaminated with blood and other potentially infectious material (OPIM) or pathogens from environmental sources such as soil, dust, and water.1,2
Cleaning is the first step in disinfection. It is a form of decontamination that renders the environmental surface safe to handle or use by removing organic matter, salts, and visible soil, all of which interfere with microbial inactivation.1,2 The physical action of scrubbing with a detergent and rinsing with water removes large amount of microorganisms from surfaces.1 A detergent, often referred to as soap, is composed of both hydrophilic and lipophilic parts and possesses cleaning properties.
There are three levels of disinfection for instruments and environmental surfaces that do not require sterility for safe use: high-level, intermediate-level, and low-level.1 The rationale for this strategy is that microorganisms can usually be grouped according to their natural resistance to a spectrum of disinfectants (Table 3).1 Disinfectants are germicidal chemicals that have been approved for use on environmental surfaces based on their efficacy against specific microorganisms.
Table 3. Levels of Disinfection by Type of Microorganism.
| Disinfection level | Bacteria | Fungi | Viruses |
|---|
| Vegetative | Tubercle bacillus | Spores | Lipid and medium size | Nonlipid and small size |
|---|
| High | + | + | ± | + | + | + |
| Intermediate | + | + | – | + | + | ± |
| Low | + | – | – | ± | + | ± |
High-level disinfectants such as glutaraldehyde, peracetic acid, and hydrogen peroxide are regulated exclusively by the FDA.1 They inactivate all vegetative bacteria, mycobacteria, viruses, fungi; and, with extended exposure times, they are capable of killing high numbers of bacterial spores. Indications for the use of high-level disinfectants are specified in their labels; for example, “use as immersion disinfectant for heat-sensitive instruments.” Their use on environmental surfaces is inappropriate.1,2
Intermediate-level disinfectants such as sodium hypochlorite, alcohols, some phenolics, and some iodophors are regulated exclusively by the EPA.1,6 Products labeled as “tuberculocidal hospital disinfectants” inactivate MBT, which is more resistant to disinfectants than ordinary vegetative bacteria, fungi, or viruses (with or without lipid envelops).1 Intermediate-level disinfectants, with the exception of sodium hypochlorite, have no sporicidal activity.
Low-level disinfectants such as quaternary ammonium compounds, some phenolics, some iodophors are also regulated exclusively by the EPA.1,6 They inactivate vegetative bacteria, fungi, enveloped viruses (e.g., HIV, HBV, influenza virus), and some non-enveloped viruses such as adenoviruses.1 Products labeled “hospital disinfectants” have passed efficacy tests for activity against Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella cholerae.1
The recent SARS CoV 2 virus pandemic heightened the focus on environmental surfaces as a reservoir for pathogens. In response, the EPA introduced a new registered disinfectant categorization: List N: Disinfectants for Use Against SARS-CoV-2.7,8 It should be noted that intermediate-level disinfectants (EPA List E) and low-level disinfectants (EPA List D) are effective in killing SARS-CoV-2.
