Matching the Right Disinfectant to the Job
By Michelle Gardner
Antimicrobials are substances used to destroy or suppress the growth of microorganisms, such as bacteria, viruses, or fungi, and are used to control infectious microorganisms on surfaces. The more commonly used antimicrobial products are sterilants, disinfectants, and sanitizers.1
It is not necessary to sterilize all patient-care items, so hospital policies must identify whether disinfection or sterilization is indicated on the basis of each item's intended use.2 The purpose of the revised Association for Professionals in Infection Control and Epidemiology (APIC) guideline is to assist healthcare professionals in their decisions involving the judicious selection and proper use of disinfectants. (See www.apic.org)
The Centers for Disease Control and Prevention (CDC) defines the three levels of disinfection in its "Guidelines for the Prevention of Transmission of Human Immunodeficiency Virus and Hepatitis B Virus to Healthcare and Public-Safety Workers." High-level disinfection can be expected to destroy all microorganisms, with the exception of high numbers of bacterial spores. Intermediate-level disinfection inactivates Mycobacterium tuberculosis, vegetative bacteria, most viruses, and most fungi, but it does not necessarily kill bacterial spores. Low-level disinfection can kill most bacteria, some viruses, and some fungi, but it cannot be relied on to kill resistant microorganisms such as tubercle bacilli or bacterial spores.
"There is a direct correlation between that level of disinfection and any given patient-care item upon which you use it," says Robert Sharbaugh, PhD, a consultant for ICP Associates in Charleston, S.C. "Not only do you have low, intermediate, and high levels of disinfectants, but you have non-critical, semi-critical, and critical categories of patient-care items. Critical items go into any sterile area of the body, including the blood vascular system. They have to be sterile. Semi-critical items will not go into a sterile area of the body, but they will come in contact with either non-intact skin or mucous membranes. Non-critical items only come into contact with intact skin, no mucous membrane contact, no sterile-body contact, and no denuded skin contact."
By definition, an intermediate-level disinfectant is one that will inactivate Mycobacterium tuberculosis and/or HIV and HBV. "If one wants to be in compliance with the bloodborne pathogen standard that OSHA promulgates, then the wise and most cost effective thing to do is to get a US Environmental Protection Agency (EPA)-registered tuberculocidal agent and use it throughout the hospital," says Sharbaugh. "The EPA has a web site (www.epa.gov/oppad001/chemregindex.htm) listing all EPA-registered tuberculocides and disinfectants that are effective against HIV and HBV."
It is difficult to determine the number of hospital-acquired infections that may be prevented by use of registered disinfectants. However, there is a great deal known about infectious microorganisms, how they spread disease, and what can be done to halt the spread of infections. For example, it is believed the most important factor in preventing the spread of diseases in hospitals is related to how often and how thoroughly HCWs wash their hands. Disinfectants and other factors may also play important roles. EPA-registered sterilants and disinfectants used in healthcare facilities are presumed to play a vital role in reducing transmission of harmful microorganisms from surfaces to people.1
A number of disinfectants are used in hospitals, including: alcohol, chlorine and chlorine compounds, formaldehyde, glutaraldehyde, hydrogen peroxide, iodophors, phenolics, and quaternary ammonium compounds. These disinfectants are not interchangeable.2 The proper selection and use of disinfectants is essential for safety and quality control. Disinfectants have various characteristics that must be considered before one is selected for a particular use.3
Alcohols demonstrate variable effectiveness against some bacterial and fungal species. They are good general-use disinfectants that are fast acting, leave no residue, and compatibly combine with other disinfectants (quaternaries, phenolics, and iodine) to form tinctures.
Aldehydes are effective against a wide spectrum of bacteria and viruses, are sporicidal when used properly (10-hour contact period), and demonstrate activity against vegetative bacteria, spores, and viruses.
Activated Glutaraldehyde requires limited and controlled use because of its toxic properties. It must only be used while wearing a ventilated hood. It has limited stability after activation (for alkaline glutaraldehyde).
Chlorine compounds are good disinfectants for the clean-up of blood or body-fluid spills. They have a biocidal effect on M. tuberculosis, S. aureus, other vegetative bacteria, and HIV after 10-20 minutes, 1:5 dilution (250 ppm) for bacterial spores and mycobacteria. Diluted chlorine bleach stored at room temperature in a closed plastic container will deteriorate by one half after one month, neutralizes rapidly in the presence of organic matter, is good for decontamination of HBV, HCV, HIV, and the clean-up of biohazardous spills. Undiluted bleach is good for surface disinfecting after possible contamination with the CJD virus; however NIH recommends 1.0 N NaOH.
Iodophor is effective against vegetative bacteria and viruses. It demonstrates poor activity against bacterial spores, however it has a rapid biocidal action. It is effective against Gram-negative and Gram-positive organisms, some viruses, and tubercle bacilli, and is most effective in acid solutions. It can vaporize at 120º F to 125º F (should not be used in hot water), and its effectiveness can be reduced by organic matter. It is stable in storage if kept cool and tightly covered. It is still active if the solution is brown or yellow.
Mercurials demonstrate poor activity against vegetative bacteria and are not effective on spores. They are toxic and not recommended for use.
Phenolic compounds are effective against vegetative bacteria, fungi, and lipid-containing viruses. They have low solubility in water, are stable in storage, are germicidal against Gram-negative and Gram-positive organisms and tubercle bacilli, are effective over a large pH range, and have limited sporicidal activity. Prolonged contact deteriorates rubber, and can cause skin and eye irritation. Not for use on food-contact surfaces.
Quaternary ammonium compounds are acceptable to control vegetative bacteria and non-lipid-containing viruses. They are stable in storage, have no odor but act as deodorizers. They are non-irritating to skin but skin or eye contact should be avoided. They are effective at temperatures up to 212º F, are effective against Gram-positive organisms, are bacteriostatic in high dilutions, are ineffective against tubercle bacilli, spores, and viruses, are more effective in alkaline than acid solutions, are neutralized by soap, and their effectiveness is reduced by organic material.