Which organisms are disinfectants effective against

The literature contains several accounts of the properties, germicidal effectiveness, and potential uses for stabilized hydrogen peroxide in the health-care setting. Published reports ascribe good germicidal activity to hydrogen peroxide and attest to its bactericidal, virucidal, sporicidal, and fungicidal properties Tables 4 and 5 The FDA website lists cleared liquid chemical sterilants and high-level disinfectants containing hydrogen peroxide and their cleared contact conditions.

Hydrogen peroxide works by producing destructive hydroxyl free radicals that can attack membrane lipids, DNA, and other essential cell components. Catalase, produced by aerobic organisms and facultative anaerobes that possess cytochrome systems, can protect cells from metabolically produced hydrogen peroxide by degrading hydrogen peroxide to water and oxygen. This defense is overwhelmed by the concentrations used for disinfection , Hydrogen peroxide is active against a wide range of microorganisms, including bacteria, yeasts, fungi, viruses, and spores 78, Bactericidal effectiveness and stability of hydrogen peroxide in urine has been demonstrated against a variety of health-care—associated pathogens; organisms with high cellular catalase activity e.

Synergistic sporicidal effects were observed when spores were exposed to a combination of hydrogen peroxide 5. Other studies demonstrated the antiviral activity of hydrogen peroxide against rhinovirus The product marketed as a sterilant is a premixed, ready-to-use chemical that contains 7.

The mycobactericidal activity of 7. When the effectiveness of 7. No complaints were received from the nursing or medical staff regarding odor or toxicity.

A new, rapid-acting Manufacturer data demonstrate that this solution sterilizes in 30 minutes and provides high-level disinfection in 5 minutes This product has not been used long enough to evaluate material compatibility to endoscopes and other semicritical devices, and further assessment by instrument manufacturers is needed.

Under normal conditions, hydrogen peroxide is extremely stable when properly stored e. Corneal damage from a hydrogen peroxide-soaked tonometer tip that was not properly rinsed has been reported Hydrogen peroxide also has been instilled into urinary drainage bags in an attempt to eliminate the bag as a source of bladder bacteriuria and environmental contamination Although the instillation of hydrogen peroxide into the bag reduced microbial contamination of the bag, this procedure did not reduce the incidence of catheter-associated bacteriuria As with other chemical sterilants, dilution of the hydrogen peroxide must be monitored by regularly testing the minimum effective concentration i.

Compatibility testing by Olympus America of the 7. Iodine solutions or tinctures long have been used by health professionals primarily as antiseptics on skin or tissue. Iodophors, on the other hand, have been used both as antiseptics and disinfectants. FDA has not cleared any liquid chemical sterilant or high-level disinfectants with iodophors as the main active ingredient.

An iodophor is a combination of iodine and a solubilizing agent or carrier; the resulting complex provides a sustained-release reservoir of iodine and releases small amounts of free iodine in aqueous solution. The best-known and most widely used iodophor is povidone-iodine, a compound of polyvinylpyrrolidone with iodine. This product and other iodophors retain the germicidal efficacy of iodine but unlike iodine generally are nonstaining and relatively free of toxicity and irritancy , Several reports that documented intrinsic microbial contamination of antiseptic formulations of povidone-iodine and poloxamer-iodine caused a reappraisal of the chemistry and use of iodophors The reason for the observation that dilution increases bactericidal activity is unclear, but dilution of povidone-iodine might weaken the iodine linkage to the carrier polymer with an accompanying increase of free iodine in solution Iodine can penetrate the cell wall of microorganisms quickly, and the lethal effects are believed to result from disruption of protein and nucleic acid structure and synthesis.

Published reports on the in vitro antimicrobial efficacy of iodophors demonstrate that iodophors are bactericidal, mycobactericidal, and virucidal but can require prolonged contact times to kill certain fungi and bacterial spores 14, , , Three brands of povidone-iodine solution have demonstrated more rapid kill seconds to minutes of S.

The virucidal activity of 75— ppm available iodine was demonstrated against seven viruses Other investigators have questioned the efficacy of iodophors against poliovirus in the presence of organic matter and rotavirus SA in distilled or tapwater Besides their use as an antiseptic, iodophors have been used for disinfecting blood culture bottles and medical equipment, such as hydrotherapy tanks, thermometers, and endoscopes. Antiseptic iodophors are not suitable for use as hard-surface disinfectants because of concentration differences.

Iodophors formulated as antiseptics contain less free iodine than do those formulated as disinfectants Iodine or iodine-based antiseptics should not be used on silicone catheters because they can adversely affect the silicone tubing Ortho-phthalaldehyde is a high-level disinfectant that received FDA clearance in October It contains 0. OPA solution is a clear, pale-blue liquid with a pH of 7. Tables 4 and 5. Preliminary studies on the mode of action of OPA suggest that both OPA and glutaraldehyde interact with amino acids, proteins, and microorganisms.

However, OPA is a less potent cross-linking agent. This is compensated for by the lipophilic aromatic nature of OPA that is likely to assist its uptake through the outer layers of mycobacteria and gram-negative bacteria OPA appears to kill spores by blocking the spore germination process Studies have demonstrated excellent microbicidal activity in vitro 69, , , , For example, OPA has superior mycobactericidal activity 5-log 10 reduction in 5 minutes to glutaraldehyde.

The mean times required to produce a 6-log 10 reduction for M. OPA showed good activity against the mycobacteria tested, including the glutaraldehyde-resistant strains, but 0. Increasing the pH from its unadjusted level about 6.

The level of biocidal activity was directly related to the temperature. A greater than 5-log 10 reduction of B. The influence of laboratory adaptation of test strains, such as P. Resistant and multiresistant strains increased substantially in susceptibility to OPA after laboratory adaptation log 10 reduction factors increased by 0. Other studies have found naturally occurring cells of P.

OPA has several potential advantages over glutaraldehyde. It has excellent stability over a wide pH range pH 3—9 , is not a known irritant to the eyes and nasal passages , does not require exposure monitoring, has a barely perceptible odor, and requires no activation. OPA, like glutaraldehyde, has excellent material compatibility. A potential disadvantage of OPA is that it stains proteins gray including unprotected skin and thus must be handled with caution Meticulous cleaning, using the correct OPA exposure time e.

Personal protective equipment should be worn when contaminated instruments, equipment, and chemicals are handled In April , the manufacturer of OPA disseminated information to users about patients who reportedly experienced an anaphylaxis-like reaction after cystoscopy where the scope had been reprocessed using OPA. Of approximately 1 million urologic procedures performed using instruments reprocessed using OPA, 24 cases 17 cases in the United States, six in Japan, one in the United Kingdom of anaphylaxis-like reactions have been reported after repeated cystoscopy typically after four to nine treatments.

Preventive measures include removal of OPA residues by thorough rinsing and not using OPA for reprocessing urologic instrumentation used to treat patients with a history of bladder cancer Nevine Erian, personal communication, June 4, ; Product Notification, Advanced Sterilization Products, April 23, A few OPA clinical studies are available. Furthermore, OPA was effective over a day use cycle High-pressure liquid chromatography confirmed that OPA levels are maintained above 0.

OPA must be disposed in accordance with local and state regulations. These label claims differ worldwide because of differences in the test methodology and requirements for licensure. Peracetic, or peroxyacetic, acid is characterized by rapid action against all microorganisms. Special advantages of peracetic acid are that it lacks harmful decomposition products i. Sterilants are biocidal, because by definition they will kill all living organisms, both pathogenic and nonpathogenic.

Microorganisms have different levels of resistance to chemical disinfection. Resistance varies with the type of organism. For instance, bacterial spores are very difficult to kill, whereas the HIV virus is rather easy to eradicate on hard surfaces. Infectious prions e. At this time there are no documented chemical or physical agents that will inactivate these infectious proteins. Similarly, there is no registered germicide that can with certainty kill pinworm eggs, although a simple ammonia solution will kill the ova of other parasites e.

Table 1 lists types of microorganisms in descending order of resistance to chemical germicides. A germicide at a given level of effectiveness should inactivate or kill all organisms located at that level and on the lower levels of resistance.

Apart from prions and parasite ova, bacterial spores are the life form that is most difficult to kill, so the Food and Drug Administration FDA uses biological indicators that contain bacterial spores to prove sterilizing efficacy.

Notice that this list does not contain protozoan cysts. Pinworm eggs are very persistent in the laboratory animal facility, and are usually able to tolerate chemical germicides.

Like an egg, they will harden and become inactive when heated. Types of microbes, listed in descending order of resistance to chemical germicides a,b. A pesticide label must include a list of active ingredients with their amounts, storage, and disposal information.

If a product does not have an EPA registration number, then it should not be used for disinfection in an animal-care area. These new regulations considered sporicides and sterilants as the same. The FDA classifies differently products that disinfect surfaces and those used to sterilize medical devices.

EPA-registered disinfectants may not be used as terminal sterilants on any surface or instrument that is introduced directly into the human body or that comes in contact with normally sterile areas of the body or the bloodstream. A sterilant sporicide is capable of destroying all forms of microbial life.

Sterilants are the most potent and are effective against all forms of vegetative bacteria, bacterial spores, fungi, fungal spores, and viruses. An FDA-registered liquid chemical sterilant will completely eradicate all of the microorganisms listed in Table 1.

A high-level disinfectant should eradicate all microbes except for bacterial spores. An intermediate-level disinfectant should eradicate enveloped viruses and all the less-resistant microbes. A low-level disinfectant must kill only three species of bacteria: Salmonella choleraesuis , Staphylococcus aureus , and Pseudomonas aeruginosa. Incredibly, there is also a category of disinfectants below that of a low-level disinfectant.

Iodine compounds are disinfectants that can kill many kinds of microorganisms, including both enveloped and nonenveloped viruses. Iodines appear to work by penetrating the cell wall of the organisms, causing a disruption of the cell metabolism and function.

Secondarily, free iodine may bond in solution with the cell proteins to form salts 4. Iodine compounds are poor cleaners, requiring the use of another chemical to clean the surface. In addition, iodines are relatively unstable in terms of contact time and light exposure, and can permanently stain surfaces if not used properly. Extensively used during the s, iodines imparted a permanent brown discoloration to floors and walls. Perhaps most importantly of all, iodophors are only active within tight brackets of concentration.

Increasing the concentration may actually reduce the available iodine in the aqueous solution 5. Additionally, microorganisms, specifically Pseudomonas cepacia, have been cultured from full-strength povidone—iodine products 6. Phenolic compounds are broad-spectrum disinfectants that can kill both enveloped and nonenveloped viruses as well as mycobacteria. These compounds are extremely corrosive and require exceptional precautions in handling.

Phenolics are extremely hazardous to cats, cause skin depigmentation, and have posed human health problems 4 , 7. In the past, the phenol coefficient has been the standard against which all other disinfectants were judged.

This standardization included comparing germicidal chemicals and provided an index to the concentration of other products. The errors inherent in converting phenol coefficient numbers to effective dilutions of products for practical disinfection are so great that the procedure must be considered unsatisfactory, particularly for nonphenolic compounds. Currently, the Association of Official Analytical Chemists AOAC use dilution test remains the standard for determining the efficacy of disinfectants; however, the government has provided funding to establish alternative assays, each with an exact number of microorganisms per challenge.

These assays should soon be adopted. Sodium hypochlorite. Sodium hypochlorite the active ingredient in bleach is perhaps the best example of a chlorine compound used as a disinfectant. If used within some rather stringent parameters, bleach is a very effective and relatively inexpensive virucidal product. The mode of action of chlorine compounds is not fully understood. Chlorine compounds may actually cause cell death by a two-step process, reacting with the cell protoplasm after forcing entry through the cell wall, or perhaps by inhibiting the cell enzyme reactions and denaturing the cell proteins 4 , 7.

Spaulding illustrated this relation when he employed identical test conditions and demonstrated that it took 30 minutes to kill 10 B. This reinforces the need for scrupulous cleaning of medical instruments before disinfection and sterilization. Reducing the number of microorganisms that must be inactivated through meticulous cleaning, increases the margin of safety when the germicide is used according to the labeling and shortens the exposure time required to kill the entire microbial load.

Researchers also have shown that aggregated or clumped cells are more difficult to inactivate than monodispersed cells The location of microorganisms also must be considered when factors affecting the efficacy of germicides are assessed. Medical instruments with multiple pieces must be disassembled and equipment such as endoscopes that have crevices, joints, and channels are more difficult to disinfect than are flat- surface equipment because penetration of the disinfectant of all parts of the equipment is more difficult.

Only surfaces that directly contact the germicide will be disinfected, so there must be no air pockets and the equipment must be completely immersed for the entire exposure period. Manufacturers should be encouraged to produce equipment engineered for ease of cleaning and disinfection. Microorganisms vary greatly in their resistance to chemical germicides and sterilization processes Figure 1 Intrinsic resistance mechanisms in microorganisms to disinfectants vary. For example, spores are resistant to disinfectants because the spore coat and cortex act as a barrier, mycobacteria have a waxy cell wall that prevents disinfectant entry, and gram-negative bacteria possess an outer membrane that acts as a barrier to the uptake of disinfectants , Implicit in all disinfection strategies is the consideration that the most resistant microbial subpopulation controls the sterilization or disinfection time.

That is, to destroy the most resistant types of microorganisms i. Except for prions, bacterial spores possess the highest innate resistance to chemical germicides, followed by coccidia e. The germicidal resistance exhibited by the gram-positive and gram-negative bacteria is similar with some exceptions e.

Rickettsiae , Chlamydiae , and mycoplasma cannot be placed in this scale of relative resistance because information about the efficacy of germicides against these agents is limited Because these microorganisms contain lipid and are similar in structure and composition to other bacteria, they can be predicted to be inactivated by the same germicides that destroy lipid viruses and vegetative bacteria.

A known exception to this supposition is Coxiella burnetti , which has demonstrated resistance to disinfectants With other variables constant, and with one exception iodophors , the more concentrated the disinfectant, the greater its efficacy and the shorter the time necessary to achieve microbial kill.

Generally not recognized, however, is that all disinfectants are not similarly affected by concentration adjustments. For example, surfactants can be added to a disinfectant formula to provide consistent wetting on a surface or to help in cleaning. Several broad categories of disinfectants are used in commercial and industrial facility maintenance.

Below are several of the most common types. While not an exhaustive list, these cover the large majority used today. Nyco has several disinfectants with this special claim. Read your disinfectant label to identify whether it has the emerging pathogen claim. There are four primary considerations you should evaluate when choosing a disinfectant to best meet the needs of your facility.

Answering these questions will give you a framework for helping determine the best product s to use in your organization. Does a disinfectant kill the microbes and pathogens that are of top concern in your facility? Some disinfectants are EPA approved as effective against this bacteria. Keep in mind that pathogens can have multiple strains, and disinfectants are certified for specific strains. Depending on your industry and facility type — healthcare, education, long-term care, hospitality — you will have varying needs and requirements.

How quickly does a disinfectant product kill a specific pathogen? Does the product keep surfaces visibly wet in order to comply with these kill times? Again, disinfectant formulas are registered to kill specific pathogens in a specific amount of time, and they need to be wet on a surface the entire time to be actively working. Thirty seconds to five minutes might be a typical kill time. If a disinfectant needs 10 minutes though, be sure it will actually stay wet that long.