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Matching the Right Disinfectant to the Job
By Michelle Gardner
Antimicrobials are substances used to destroy or suppress the growth ofmicroorganisms, such as bacteria, viruses, or fungi, and are used to controlinfectious microorganisms on surfaces. The more commonly used antimicrobialproducts are sterilants, disinfectants, and sanitizers.1
It is not necessary to sterilize all patient-care items, so hospital policiesmust identify whether disinfection or sterilization is indicated on the basis ofeach item's intended use.2 The purpose of the revised Association forProfessionals in Infection Control and Epidemiology (APIC) guideline is toassist healthcare professionals in their decisions involving the judiciousselection and proper use of disinfectants. (See www.apic.org)
The Centers for Disease Control and Prevention (CDC) defines the three levelsof disinfection in its "Guidelines for the Prevention of Transmission ofHuman Immunodeficiency Virus and Hepatitis B Virus to Healthcare andPublic-Safety Workers." High-level disinfection can be expected todestroy all microorganisms, with the exception of high numbers of bacterialspores. Intermediate-level disinfection inactivates Mycobacteriumtuberculosis, vegetative bacteria, most viruses, and most fungi, but it doesnot necessarily kill bacterial spores. Low-level disinfection can killmost bacteria, some viruses, and some fungi, but it cannot be relied on to killresistant microorganisms such as tubercle bacilli or bacterial spores.
"There is a direct correlation between that level of disinfection andany 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 youhave low, intermediate, and high levels of disinfectants, but you havenon-critical, semi-critical, and critical categories of patient-care items.Critical items go into any sterile area of the body, including the bloodvascular system. They have to be sterile. Semi-critical items will not go into asterile area of the body, but they will come in contact with either non-intactskin or mucous membranes. Non-critical items only come into contact with intactskin, no mucous membrane contact, no sterile-body contact, and no denuded skincontact."
By definition, an intermediate-level disinfectant is one that will inactivateMycobacterium tuberculosis and/or HIV and HBV. "If one wants to bein compliance with the bloodborne pathogen standard that OSHA promulgates, thenthe wise and most cost effective thing to do is to get a US EnvironmentalProtection Agency (EPA)-registered tuberculocidal agent and use it throughoutthe hospital," says Sharbaugh. "The EPA has a web site (www.epa.gov/oppad001/chemregindex.htm)listing all EPA-registered tuberculocides and disinfectants that are effectiveagainst HIV and HBV."
It is difficult to determine the number of hospital-acquired infections thatmay be prevented by use of registered disinfectants. However, there is a greatdeal known about infectious microorganisms, how they spread disease, and whatcan be done to halt the spread of infections. For example, it is believed themost important factor in preventing the spread of diseases in hospitals isrelated to how often and how thoroughly HCWs wash their hands. Disinfectants andother factors may also play important roles. EPA-registered sterilants anddisinfectants used in healthcare facilities are presumed to play a vital role inreducing transmission of harmful microorganisms from surfaces to people.1
A number of disinfectants are used in hospitals, including: alcohol, chlorineand chlorine compounds, formaldehyde, glutaraldehyde, hydrogen peroxide,iodophors, phenolics, and quaternary ammonium compounds. These disinfectants arenot interchangeable.2 The proper selection and use of disinfectantsis essential for safety and quality control. Disinfectants have variouscharacteristics that must be considered before one is selected for a particularuse.3
Alcohols demonstrate variable effectiveness against some bacterial andfungal 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 andviruses, are sporicidal when used properly (10-hour contact period), anddemonstrate activity against vegetative bacteria, spores, and viruses.
Activated Glutaraldehyde requires limited and controlled use becauseof 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 orbody-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 storedat room temperature in a closed plastic container will deteriorate by one halfafter one month, neutralizes rapidly in the presence of organic matter, is goodfor decontamination of HBV, HCV, HIV, and the clean-up of biohazardous spills.Undiluted bleach is good for surface disinfecting after possible contaminationwith the CJD virus; however NIH recommends 1.0 N NaOH.
Iodophor is effective against vegetative bacteria and viruses. Itdemonstrates poor activity against bacterial spores, however it has a rapidbiocidal action. It is effective against Gram-negative and Gram-positiveorganisms, some viruses, and tubercle bacilli, and is most effective in acidsolutions. It can vaporize at 120Âº F to 125Âº F (should not be used in hotwater), and its effectiveness can be reduced by organic matter. It is stable instorage if kept cool and tightly covered. It is still active if the solution isbrown or yellow.
Mercurials demonstrate poor activity against vegetative bacteria andare 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 instorage, are germicidal against Gram-negative and Gram-positive organisms andtubercle bacilli, are effective over a large pH range, and have limitedsporicidal activity. Prolonged contact deteriorates rubber, and can cause skinand eye irritation. Not for use on food-contact surfaces.
Quaternary ammonium compounds are acceptable to control vegetativebacteria and non-lipid-containing viruses. They are stable in storage, have noodor but act as deodorizers. They are non-irritating to skin but skin or eyecontact should be avoided. They are effective at temperatures up to 212Âº F, areeffective against Gram-positive organisms, are bacteriostatic in high dilutions,are ineffective against tubercle bacilli, spores, and viruses, are moreeffective in alkaline than acid solutions, are neutralized by soap, and theireffectiveness is reduced by organic material.