This is a two-part answer:. These two factors mean that when you mix water and ethanol, the ethanol molecules occupy the space between the water molecules. For everyday lab life, you need only to remember that fluid volumes i. Has this helped you? Then please share with your network. There are an abundance of studies showing efficacy rates of various alcohols at different concentrations.
Its cheaper, Its less flammable, Less vocs. It evaporates slower and therefore requires fewer applications. We have anhydrous ethanol that is expired. I understand that this solution is hygroscopic and while the cap is always on, we likely now have a lower alcohol percentage than we did originally. Is this the only thing to be concerned about? If so, is there some equilibrium that such a solution would come to that would define the ethanol:water ratio?
For your information, the makeup palette is skin illustrator. Alcohols have been used to disinfect fiberoptic endoscopes , but failure of this disinfectant have lead to infection , Alcohol towelettes have been used for years to disinfect small surfaces such as rubber stoppers of multiple-dose medication vials or vaccine bottles. Furthermore, alcohol occasionally is used to disinfect external surfaces of equipment e. In contrast, three bloodstream infection outbreaks have been described when alcohol was used to disinfect transducer heads in an intensive-care setting The documented shortcomings of alcohols on equipment are that they damage the shellac mountings of lensed instruments, tend to swell and harden rubber and certain plastic tubing after prolonged and repeated use, bleach rubber and plastic tiles and damage tonometer tips by deterioration of the glue after the equivalent of 1 working year of routine use Tonometer biprisms soaked in alcohol for 4 days developed rough front surfaces that potentially could cause corneal damage; this appeared to be caused by weakening of the cementing substances used to fabricate the biprisms Corneal opacification has been reported when tonometer tips were swabbed with alcohol immediately before measurement of intraocular pressure Alcohols are flammable and consequently must be stored in a cool, well-ventilated area.
They also evaporate rapidly, making extended exposure time difficult to achieve unless the items are immersed. Hypochlorites, the most widely used of the chlorine disinfectants, are available as liquid e. The most prevalent chlorine products in the United States are aqueous solutions of 5.
They have a broad spectrum of antimicrobial activity, do not leave toxic residues, are unaffected by water hardness, are inexpensive and fast acting , remove dried or fixed organisms and biofilms from surfaces , and have a low incidence of serious toxicity Sodium hypochlorite at the concentration used in household bleach 5.
The microbicidal activity of chlorine is attributed largely to undissociated hypochlorous acid HOCl. A potential hazard is production of the carcinogen bis chloromethyl ether when hypochlorite solutions contact formaldehyde and the production of the animal carcinogen trihalomethane when hot water is hyperchlorinated After reviewing environmental fate and ecologic data, EPA has determined the currently registered uses of hypochlorites will not result in unreasonable adverse effects to the environment Alternative compounds that release chlorine and are used in the health-care setting include demand-release chlorine dioxide, sodium dichloroisocyanurate, and chloramine-T.
The advantage of these compounds over the hypochlorites is that they retain chlorine longer and so exert a more prolonged bactericidal effect. Sodium dichloroisocyanurate tablets are stable, and for two reasons, the microbicidal activity of solutions prepared from sodium dichloroisocyanurate tablets might be greater than that of sodium hypochlorite solutions containing the same total available chlorine.
Second, solutions of sodium dichloroisocyanurate are acidic, whereas sodium hypochlorite solutions are alkaline, and the more microbicidal type of chlorine HOCl is believed to predominate Chlorine dioxide-based disinfectants are prepared fresh as required by mixing the two components base solution [citric acid with preservatives and corrosion inhibitors] and the activator solution [sodium chlorite].
In vitro suspension tests showed that solutions containing about ppm chlorine dioxide achieved a reduction factor exceeding 10 6 of S. The potential for damaging equipment requires consideration because long-term use can damage the outer plastic coat of the insertion tube In another study, chlorine dioxide solutions at either ppm or 30 ppm killed Mycobacterium avium-intracellulare within 60 seconds after contact but contamination by organic material significantly affected the microbicidal properties The main products of this water are hypochlorous acid e.
As with any germicide, the antimicrobial activity of superoxidized water is strongly affected by the concentration of the active ingredient available free chlorine One manufacturer generates the disinfectant at the point of use by passing a saline solution over coated titanium electrodes at 9 amps. The product generated has a pH of 5. Although superoxidized water is intended to be generated fresh at the point of use, when tested under clean conditions the disinfectant was effective within 5 minutes when 48 hours old Unfortunately, the equipment required to produce the product can be expensive because parameters such as pH, current, and redox potential must be closely monitored.
The solution is nontoxic to biologic tissues. Although the United Kingdom manufacturer claims the solution is noncorrosive and nondamaging to endoscopes and processing equipment, one flexible endoscope manufacturer Olympus Key-Med, United Kingdom has voided the warranty on the endoscopes if superoxidized water is used to disinfect them As with any germicide formulation, the user should check with the device manufacturer for compatibility with the germicide.
Additional studies are needed to determine whether this solution could be used as an alternative to other disinfectants or antiseptics for hand washing, skin antisepsis, room cleaning, or equipment disinfection e. The exact mechanism by which free chlorine destroys microorganisms has not been elucidated. Inactivation by chlorine can result from a number of factors: oxidation of sulfhydryl enzymes and amino acids; ring chlorination of amino acids; loss of intracellular contents; decreased uptake of nutrients; inhibition of protein synthesis; decreased oxygen uptake; oxidation of respiratory components; decreased adenosine triphosphate production; breaks in DNA; and depressed DNA synthesis , The actual microbicidal mechanism of chlorine might involve a combination of these factors or the effect of chlorine on critical sites Low concentrations of free available chlorine e.
Higher concentrations 1, ppm of chlorine are required to kill M. One study reported that 25 different viruses were inactivated in 10 minutes with ppm available chlorine Several studies have demonstrated the effectiveness of diluted sodium hypochlorite and other disinfectants to inactivate HIV Chlorine ppm showed inhibition of Candida after 30 seconds of exposure Because household bleach contains 5.
A chlorine dioxide generator has been shown effective for decontaminating flexible endoscopes but it is not currently FDA-cleared for use as a high-level disinfectant Chlorine dioxide can be produced by mixing solutions, such as a solution of chlorine with a solution of sodium chlorite In , a chlorine dioxide product was voluntarily removed from the market when its use caused leakage of cellulose-based dialyzer membranes, which allowed bacteria to migrate from the dialysis fluid side of the dialyzer to the blood side However, the biocidal activity of this disinfectant decreased substantially in the presence of organic material e.
No bacteria or viruses were detected on artificially contaminated endoscopes after a 5-minute exposure to superoxidized water and HBV-DNA was not detected from any endoscope experimentally contaminated with HBV-positive mixed sera after a disinfectant exposure time of 7 minutes Hypochlorites are widely used in healthcare facilities in a variety of settings. A — dilution of 5. For small spills of blood i. Because hypochlorites and other germicides are substantially inactivated in the presence of blood 63, , , , large spills of blood require that the surface be cleaned before an EPA-registered disinfectant or a final concentration solution of household bleach is applied If a sharps injury is possible, the surface initially should be decontaminated 69, , then cleaned and disinfected final concentration Extreme care always should be taken to prevent percutaneous injury.
At least ppm available chlorine for 10 minutes is recommended for decontaminating CPR training manikins Full-strength bleach has been recommended for self-disinfection of needles and syringes used for illicit-drug injection when needle-exchange programs are not available. The difference in the recommended concentrations of bleach reflects the difficulty of cleaning the interior of needles and syringes and the use of needles and syringes for parenteral injection Clinicians should not alter their use of chlorine on environmental surfaces on the basis of testing methodologies that do not simulate actual disinfection practices , Other uses in healthcare include as an irrigating agent in endodontic treatment and as a disinfectant for manikins, laundry, dental appliances, hydrotherapy tanks 23, 41 , regulated medical waste before disposal , and the water distribution system in hemodialysis centers and hemodialysis machines Chlorine long has been used as the disinfectant in water treatment.
Water disinfection with monochloramine by municipal water-treatment plants substantially reduced the risk for healthcare—associated Legionnaires disease , Chlorine dioxide also has been used to control Legionella in a hospital water supply. Thus, if a user wished to have a solution containing ppm of available chlorine at day 30, he or she should prepare a solution containing 1, ppm of chlorine at time 0.
Sodium hypochlorite solution does not decompose after 30 days when stored in a closed brown bottle The use of powders, composed of a mixture of a chlorine-releasing agent with highly absorbent resin, for disinfecting spills of body fluids has been evaluated by laboratory tests and hospital ward trials.
The inclusion of acrylic resin particles in formulations markedly increases the volume of fluid that can be soaked up because the resin can absorb — times its own weight of fluid, depending on the fluid consistency. One problem with chlorine-releasing granules is that they can generate chlorine fumes when applied to urine Formaldehyde is used as a disinfectant and sterilant in both its liquid and gaseous states. Liquid formaldehyde will be considered briefly in this section, and the gaseous form is reviewed elsewhere The aqueous solution is a bactericide, tuberculocide, fungicide, virucide and sporicide 72, 82, OSHA indicated that formaldehyde should be handled in the workplace as a potential carcinogen and set an employee exposure standard for formaldehyde that limits an 8-hour time-weighted average exposure concentration of 0.
The standard includes a second permissible exposure limit in the form of a short-term exposure limit STEL of 2 ppm that is the maximum exposure allowed during a minute period Ingestion of formaldehyde can be fatal, and long-term exposure to low levels in the air or on the skin can cause asthma-like respiratory problems and skin irritation, such as dermatitis and itching.
For these reasons, employees should have limited direct contact with formaldehyde, and these considerations limit its role in sterilization and disinfection processes.
Formaldehyde inactivates microorganisms by alkylating the amino and sulfhydral groups of proteins and ring nitrogen atoms of purine bases Varying concentrations of aqueous formaldehyde solutions destroy a wide range of microorganisms. Four percent formaldehyde is a tuberculocidal agent, inactivating 10 4 M. The formaldehyde solution required 2 hours of contact to achieve an inactivation factor of 10 4 , whereas glutaraldehyde required only 15 minutes.
For these reasons and others—such as its role as a suspected human carcinogen linked to nasal cancer and lung cancer , this germicide is excluded from Table 1. When it is used, , direct exposure to employees generally is limited; however, excessive exposures to formaldehyde have been documented for employees of renal transplant units , , and students in a gross anatomy laboratory Formaldehyde is used in the health-care setting to prepare viral vaccines e.
To minimize a potential health hazard to dialysis patients, the dialysis equipment must be thoroughly rinsed and tested for residual formaldehyde before use. Paraformaldehyde, a solid polymer of formaldehyde, can be vaporized by heat for the gaseous decontamination of laminar flow biologic safety cabinets when maintenance work or filter changes require access to the sealed portion of the cabinet. Glutaraldehyde is a saturated dialdehyde that has gained wide acceptance as a high-level disinfectant and chemical sterilant Aqueous solutions of glutaraldehyde are acidic and generally in this state are not sporicidal.
Once activated, these solutions have a shelf-life of minimally 14 days because of the polymerization of the glutaraldehyde molecules at alkaline pH levels.
This polymerization blocks the active sites aldehyde groups of the glutaraldehyde molecules that are responsible for its biocidal activity. Novel glutaraldehyde formulations e. However, antimicrobial activity depends not only on age but also on use conditions, such as dilution and organic stress. However, two studies found no difference in the microbicidal activity of alkaline and acid glutaraldehydes 73, The biocidal activity of glutaraldehyde results from its alkylation of sulfhydryl, hydroxyl, carboxyl, and amino groups of microorganisms, which alters RNA, DNA, and protein synthesis.
The mechanism of action of glutaraldehydes are reviewed extensively elsewhere , The in vitro inactivation of microorganisms by glutaraldehydes has been extensively investigated and reviewed , Spores of C.
Microorganisms with substantial resistance to glutaraldehyde have been reported, including some mycobacteria M. Two percent alkaline glutaraldehyde solution inactivated 10 5 M.
However, subsequent studies 82 questioned the mycobactericidal prowess of glutaraldehydes. Suspensions of M. IPA isopropyl alcohol. Viable bacteria remained at all concentrations of both ethanol and isopropyl alcohol with a range up to 2.
NS exposure yielded 2. For S. Cell counts were not significantly reduced by alcohol exposure for any of the S. For all strains, viable cell count tended to decrease with increasing alcohol concentration, but these differences were not statistically significant. Our results are similar to a previous study demonstrating increased S. We found these bacteria within biofilm were viable, although viability was decreased compared to NS-exposed biofilm.
In contrast to previous reports [ 4 , 19 ], bacteria in biofilm were not eradicated after alcohol exposure. This may be due to different methods used to remove the biofilm from 96 well plates, as prior studies removed biofilm using cotton swabs [ 4 , 19 ], whereas we sonicated the well plates.
We also found an increase in biofilm formation with increasing alcohol concentration. Only one strain, the prolific biofilm-forming S. This strain was likely near maximal biofilm production possible in this assay.
Small variations in biofilm formation are possible, as demonstrated by the differences in NS-exposed biofilm between the ethanol and isopropyl alcohol experiments. The bactericidal effect of alcohol depends upon dehydration and denaturation of proteins [ 20 ]. Ethanol also causes leakage of the plasma membrane, disrupting bacterial growth and metabolism [ 22 ].
The impact of dehydration on cell death in the presence of alcohols may not be observed in catheter lock solutions since these do not dry, however denatured proteins and leaking membranes may still lead to decreased viability. The high concentrations of ethanol in catheter lock solutions increase biofilm formation in Staphylococci and also predisposes to catheter dysfunction and plasma protein precipitation [ 6 ].
Staphylococcus epidermidis M7, the isogenic slime-negative, biofilm-deficient mutant of S. M7, sometimes referred to as an accumulation-negative mutant, is distinguished from ATCC because it lacks a kDa antigen called accumulation-associated protein, but it has been found to have a kDa protein with similar homology [ 23 , 24 ]. This strain does not accumulate on glass and polystyrene surfaces [ 23 ], but it accumulates on polyvinyl chloride disks and has been shown to produce biofilm [ 25 — 28 ].
The exact mechanism for the mutation is unknown but is believed to be due to alteration of the intercellular adhesin ica gene [ 10 ]. The ica gene regulates production of polysaccharide intercellular adhesin, the major exopolysaccharide produced in S.
Ethanol increases Staphylococcal biofilm formation by increasing ica expression through modulation of the repressor, icaR [ 2 , 3 , 29 , 30 ]. It is possible that alcohol exposure and subsequent increase in ica expression allowed accumulation and biofilm formation of this strain in polystyrene plates. To our knowledge, this is the first report of any alcohol exposure to cause the M7 strain to increase biofilm formation. Regarding limitations, we tested a small number of strains, including one clinical isolate which may have different biofilm-forming behavior.
The crystal violet used in this study stains cells and does not differentiate between viable and nonviable cells or quantify extracellular matrix production. Also, we did not characterize the composition or matrix production of the biofilms. We considered that alcohol may denature bacteria in biofilm, allowing for greater penetration of the crystal violet.
However, differences in biofilm formation could be observed between wells even before the crystal violet stain was added. This also would not account for the increase in ica expression noted previously [ 30 ]. Viability may be underestimated using this method, since some adherent cells were visible in the bottom of wells after 20 min of sonication, particularly the prolific biofilm-forming ATCC Sonication of well plates can fail to release cells completely [ 31 ].
There was also a tendency for the number of bacteria to be higher in the center of the well plate than along the edges where evaporation was higher, further suggesting that dehydration played a role in cell viability.
Staphylococci exposed to clinically relevant concentrations of ethanol and isopropyl alcohol increase biofilm formation; however, the viability of these biofilm-embedded bacteria was diminished.
Future research should determine the impact of these findings on the use of various alcohol preparations in the management and prevention of infections due to biofilm-forming Staphylococci. We gratefully acknowledge Kayla Babcock and Katie Daffinee for laboratory assistance. All named authors meet the International Committee of Medical Journal Editors ICMJE criteria for authorship for this manuscript, take responsibility for the integrity of the work as a whole, and have given final approval to the version to be published.
The views expressed are those of the authors and do not necessarily represent the position or policy of the United States Department of Veterans Affairs. Megan Luther declares research funding from Pfizer and Cubist. Sarah Bilida declares no conflict of interest. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author s and the source are credited.
National Center for Biotechnology Information , U. Journal List Infect Dis Ther v. Infect Dis Ther. Published online May 3. Megan K. Luther , 1, 2 Sarah Bilida , 3 Leonard A.
Mermel , 1, 4, 5 and Kerry L. LaPlante 1, 2, 4. Leonard A. Kerry L. Author information Article notes Copyright and License information Disclaimer. LaPlante, Email: ude. Corresponding author.
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