Process for removing dry surface biofilm
12012574 ยท 2024-06-18
Assignee
Inventors
Cpc classification
C11D3/392
CHEMISTRY; METALLURGY
C11D3/3418
CHEMISTRY; METALLURGY
A01N59/00
HUMAN NECESSITIES
C11D3/30
CHEMISTRY; METALLURGY
C11D3/48
CHEMISTRY; METALLURGY
C11D17/06
CHEMISTRY; METALLURGY
C11D1/722
CHEMISTRY; METALLURGY
A01N59/00
HUMAN NECESSITIES
International classification
C11D3/48
CHEMISTRY; METALLURGY
C11D1/14
CHEMISTRY; METALLURGY
C11D1/722
CHEMISTRY; METALLURGY
C11D17/06
CHEMISTRY; METALLURGY
C11D3/30
CHEMISTRY; METALLURGY
Abstract
The present invention relates to a process for removing dry surface biofilm from a surface. The process comprises: (i) dissolving a powder-based composition into water wherein the powder-based composition comprises: a) a hydrogen peroxide source, b) an acetyl donor, c) an acidifying agent, and d) a wetting agent; (ii) allowing the solution to generate a biocidally effective concentration of peracetic acid; (iii) contacting the dry surface biofilm contaminated surface with the solution of peracetic acid for a period of time; and (iv) removing the solution.
Claims
1. A process for removing dry surface biofilm from a contaminated environmental surface or a contaminated non-critical medical device, said dry surface biofilm comprising embedded bacteria and protein and being formed by dehydration of biofilm, which process comprises: dissolving a single-part powder-based composition into water to produce a solution, wherein the powder-based composition consists essentially of: a) a hydrogen peroxide source, b) an acetyl donor, c) an acidifying agent, and d) a surfactant; (ii) allowing the solution to generate peracetic acid in a concentration of at least 0.13%; (iii) contacting the contaminated environmental surface or the contaminated non-critical medical device with the solution containing said generated peracetic acid for a period of time sufficient to kill said embedded bacteria and remove a portion of said protein present in said dry surface biofilm; and (iv) removing the solution and said dry surface biofilm from the contaminated environmental surface or the contaminated non-critical medical device.
2. A process according to claim 1 wherein the powder-based composition additionally comprises one or more ingredients selected from the group consisting of a sequestering agent, a buffering agent, a flow modifier, a colourant and a perfume.
3. A process according to claim 1 wherein the solution is removed by rinsing off or wiping off.
4. A process according to claim 1 wherein the hydrogen peroxide source is selected from the group consisting of sodium perborate, sodium percarbonate, urea peroxide, povidone-hydrogen peroxide, calcium peroxide, hydrogen peroxide solution, and combinations thereof.
5. A process according to claim 1 wherein the acetyl donor is selected from the group consisting of tetraacetylethylenediamine (TAED), N-acetyl caprolactam, N-acetyl succinimide, N-acetyl phthalimide, N-acetyl maleimide, pentaacetyl glucose, octaacetyl sucrose, acetylsalicylic acid, tetraacetyl glycouril, and combinations thereof.
6. A process according to claim 1 wherein the acidifying agent is selected from the group consisting of citric acid, monosodium citrate, disodium citrate, tartaric acid, monosodium tartrate, sulfamic acid, sodium hydrogen sulphate, monosodium phosphate, oxalic acid, benzoic acid, benzenesulfonic acid, toluene sulfonic acid and combinations thereof.
7. A process according to claim 1 wherein the surfactant is selected from the group consisting of sodium dodecyl sulphate, Pluronic PE6800, Hyamine 1620 etc, and combinations thereof.
8. A process according to claim 2 wherein the sequestering agent is selected from the group consisting of sodium citrate, citric acid, phosphoric acid, sodium tripolyphosphate, EDTA, NTA, and combinations thereof.
9. A process according to claim 2 wherein the buffering agent is selected from the group consisting of phosphate, borate, bicarbonate, TAPS (3-{[tri s(hydroxymethyl)methyl]amino}propanesulfonic acid), Bicine (N,N-bis(2-hydroxyethyl)glycine), Tris (tris(hydroxymethyl)methylamine), Tricine (N-tris(hydroxymethyl)methylglycine) and combinations thereof.
10. A process according to claim 1 wherein the contaminated environmental surface or the contaminated non-critical medical device is contacted with the solution for at least 5 minutes.
11. A process according to claim 1 wherein the powder-based composition further comprises a peracetic acid bleachable dye that discharges color when the solution reaches and obtains the concentration of peracetic acid of at least 0.13%.
12. A process according to claim 11 wherein the peracetic acid bleachable dye is a 1-arylazo-2-hydroxynaphthyl dye.
13. A process according to claim 12 wherein the peracetic acid bleachable dye is selected from the group consisting of Amaranth (CI 16185), Ponceau 4R (CI 16255), or any other 1-arylazo-2-hydroxynaphthyl dye, and combinations thereof.
14. A process according to claim 11 wherein the powder-based composition further comprises a substantially bleach-stable dye.
15. A process according to claim 14 wherein the substantially bleach-stable dye is selected from the group consisting of Acid Blue 182, Acid Blue 80, Direct Blue 86, Acid Green 25 (CI 61570), and combinations thereof.
16. A process for removing dry surface biofilm from a contaminated environmental surface or a contaminated non-critical medical device, said dry surface biofilm comprising embedded bacteria and protein and being formed by dehydration of said bacteria, which process comprises: dissolving a single-part powder-based composition into water to produce a solution, wherein the powder-based composition consists of: a) a hydrogen peroxide source, b) an acetyl donor, c) an acidifying agent, d) a surfactant, and e) optionally one or more ingredients selected from the group consisting of a sequestering agent, a buffering agent, a flow modifier, a colourant and a perfume; (ii) allowing the solution to generate peracetic acid in a concentration of at least 0.13%; (iii) contacting the contaminated environmental surface or the contaminated non-critical medical device with the solution containing said generated peracetic acid for a period of time sufficient to kill said embedded bacteria and remove a portion of said protein present in said dry surface biofilm; and (iv) removing the solution and said dry surface biofilm from the contaminated environmental surface or the contaminated non-critical medical device.
17. A process according to claim 16 wherein the powder-based composition includes one or more colourants, and wherein the one or more colourants include a peracetic acid bleachable dye that discharges color when the solution reaches and obtains the concentration of peracetic acid of at least 0.13%.
18. A process according to claim 16 wherein the contaminated environmental surface or the contaminated non-critical medical device is contacted with the solution for at least 5 minutes.
Description
BRIEF DESCRIPTION OF DRAWINGS
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DETAILED DESCRIPTION
(10) It has unexpectedly been discovered that the disinfecting composition described in the applicant's earlier U.S. application Ser. No. 15/035,633 (633) may be used as a dry surface biofilm remover.
(11) U.S. Ser. No. 15/035,633, the contents of which is incorporated herein by reference, describes a composition which, on dissolution in a solvent, generates a biocidally effective disinfectant solution comprising peracetic acid and hydrogen peroxide. The composition comprises a system to produce a visual indication of the formation of the peracetic acid. The indication is provided by a dye that is rapidly bleached in the presence of peracetic acid, whilst being substantially unaffected by the presence of hydrogen peroxide. An optional second dye may be incorporated, wherein the second dye is not substantially bleached by either peracetic acid or hydrogen peroxide.
(12) Preferably the composition of '633 is provided in a powder. Preferably the composition of '633 is dissolved in water.
(13) When the composition of '633 is presented in powdered form, it may also contain a flow modifier to prevent clumping of the powder prior to dispersion and dissolution into the solvent, and a wetting agent to assist in the rapid dispersion and dissolution of the acetyl source into solution, preferably at ambient temperature.
(14) The composition of '633 may also be packaged into a soluble sachet wherein the entire sachet and contents is placed into a solvent, preferably water, to generate the disinfectant, thus mitigating occupational exposure to the potentially harmful powder precursor.
(15) In a preferred embodiment of '633, there is provided a composition comprising a hydrogen peroxide source, an acetyl donor, an acidifying agent, and a first dye that is bleached in the presence of peracetic acid, but not hydrogen peroxide. In another embodiment, a second dye that is substantially bleach-stable may also be included in the composition of '633.
(16) In a particularly preferred embodiment of '633, the first dye is a dye that is bleached in the presence of a biocidal concentration of peracetic acid, and the second dye is a dye that is bleached after several hours in the presence of a biocidal concentration of peracetic acid. The presence of the first dye in the solution acts as a visual indication that the solution has not yet achieved the desired biocidal concentration of peracetic acid. Once the colour due to the first dye is discharged, the colour due to the second dye is left to provide an aesthetically pleasing colouration. When the composition of '633 is in powder form, it is dissolved in a solvent, preferably water, to form the peracetic acid-containing solution.
(17) The composition of '633 may also optionally contain wetting agents, sequestering and chelating agents, and other ingredients, such as bleach-stable fragrances, corrosion inhibitors, powder flow modifiers, rheology modifiers etc.
(18) The composition of '633 is prepared by combining the ingredients together. In a preferred embodiment, the composition of '633 is in powder form.
(19) In an alternative embodiment, the composition of '633 may be presented in kit form, where the hydrogen peroxide source, part (a), is stored separately to a mixture of the acetyl source and peracetic acid bleachable dye, parts (b) and (c). In use, the hydrogen peroxide source is mixed with the acetyl source/peracetic acid bleachable dye mixture, in solution.
(20) In use, the composition of '633 is dissolved in a solvent and to produce a broad spectrum disinfectant solution which is efficacious against spores, bacteria fungus, virus, yeasts and moulds. The disinfectant solution is particularly efficacious against spore forming bacteria such as Clostridium difficile. The disinfectant may be used to disinfect surfaces, including hard surfaces, and instruments.
(21) It has unexpectedly been discovered that the disinfecting composition described in '633 may be used as a dry surface biofilm remover.
(22) When a surface coated in a dry surface biofilm is contacted with a solution of peracetic acid generated by dissolving the compositions taught in '633 it has been observed that there is a significant reduction in viable bacteria, along with a substantial removal of the protein typically associated with the dry surface biofilm.
(23) This observation is all the more remarkable given that detergent solutions demonstrated to remove normal, wet surface biofilm have very little effect in removing dry surface biofilm (see Example 10). In this screening test it was also observed that chlorine-based disinfectants were also effective in removing dry surface biofilm under clean conditions. However further testing showed that the presence of an organic proteinaceous soil rapidly deactivated the chlorine, and thus resulted in little or no bacterial kill (see
(24) The disinfecting composition described in the '633 document is a powder-based formulation comprising a hydrogen peroxide donor, and acetyl donor, along with acidifying agents, wetting agents, along with optional ingredients such as additional sequestrants and perfumes.
(25) The compositions of '633 also contain a peracetic acid (PAA) bleachable dye to serve as an indicator as to when a biocidally active concentration of peracetic acid has been generated. For the avoidance of confusion, a biocidally active concentration of peracetic acid is defined as a concentration of peracetic acid above 1300 ppm.
(26) Whilst the teachings of '633 are directed towards peracetic acid generating compositions containing an indicator system comprising a peracetic acid bleachable dye, a person generally skilled in the art will recognise that the presence or absence of this indicator will not affect the biocidal performance of the peracetic acid generating compositions.
(27) The present invention is directed to a process for removing dry surface biofilm from a surface.
(28) According to the present invention, there is provided a process for removing dry surface biofilm from a surface, which process comprises:
(29) (i) dissolving a powder-based composition into water wherein the powder-based composition comprises: a) a hydrogen peroxide source b) an acetyl donor c) an acidifying agent, and d) a wetting agent
(30) (ii) allowing the solution to generate a biocidally effective concentration of peracetic acid;
(31) (iii) contacting the dry surface biofilm contaminated surface with the solution of peracetic acid for a period of time; and
(32) (iv) removing the solution.
(33) In other preferred embodiments, the powder-based formulation may be in the form of a tablet. In this case, the composition may also contain disintegrants. An example of a tabletted formulation is given in example 16 of '633.
(34) Typically, the composition of '633, as used in the process of the present invention, contains the following ingredients:
(35) Hydrogen Peroxide Source
(36) Examples of a hydrogen peroxide source which may be used in the composition of '633 and in the present invention include, but are not limited to, sodium perborate, sodium percarbonate, urea peroxide, povidone-hydrogen peroxide, calcium peroxide, and combinations thereof.
(37) A dilute solution of hydrogen peroxide in water may also be used as a hydrogen peroxide source, if a two part product is intended. In this case, the hydrogen peroxide solution should preferably contain less than 8% hydrogen peroxide, thus negating classification as a Class 5.1 Dangerous Good. The dilute solution of hydrogen peroxide may also contain additional stabilising ingredients, such as 1-hydroxyethylidene-1,1,-diphosphonic acid, (sold as Dequest 2010), or other strongly chelating additives, such as ethylenediamine tetraacetic acid (EDTA). The peroxide solution may optionally contain pH buffering agents.
(38) Acetyl Donors
(39) Examples of acetyl donors which may be used in the composition of '633 and in the present invention include, but are not limited to, tetraacetylethylenediamine (TAED), N-acetyl caprolactam, N-acetyl succinimide, N-acetyl phthalimide, N-acetyl maleimide, penta-acetyl glucose, octaacetyl sucrose, acetylsalicylic acid, tetraacetyl glycouril, and combinations thereof. Preferably the acetyl donor is a solid. The acetyl donor is understood as being an uncoated material unless otherwise indicated.
(40) A preferred acetyl donor is TAED, more particularly, a micronized grade of TAED, such as B675, obtainable from Warwick Chemicals (UK).
(41) Acidifying Agents
(42) Examples of acidifying agents which may be used in the composition of '633 and in the present invention include, but are not limited to, citric acid, monosodium citrate, disodium citrate, tartaric acid, monosodium tartrate, sulfamic acid, sodium hydrogen sulphate, monosodium phosphate, oxalic acid, benzoic acid, benzenesulfonic acid, toluenesulfonic acid and combinations thereof. Preferably the acidifying agent is a solid.
(43) Peracetic Acid Bleachable Dyes
(44) The first dye is a peracetic acid bleachable dye. Examples of peracetic acid bleachable dyes which may be used in the composition of '633 and in the present invention include Amaranth (C.I. 16185), Ponceau 4R (C.I. 16255), FD&C Yellow 6 (C.I. 15985), any other 1-arylazo-2-hydroxynaphthyl dye, and combinations thereof.
(45) The peracetic acid bleachable dye is preferably relatively rapidly bleached in the presence of peracetic acid, but not hydrogen peroxide. By relatively rapidly is meant that the colour of the dye is bleached within about 10 minutes. When the colour generated by the peracetic acid bleachable dye in solution is substantially discharged, the peracetic acid has reached a biocidally effective concentration in the solution. By substantially discharged is meant that the colour in the solution, generated by the peracetic acid bleachable dye, is entirely, or almost entirely, discharged.
(46) In a preferred embodiment of the composition of '633, as used in the present invention, the first dye is Amaranth Red (C.I. 16185) and the second dye is C.I. Acid Blue 182. Surprisingly, it has been found that in this embodiment, Amaranth Red is bleached rapidly by only peracetic acid, whilst being relatively resistant to bleaching by hydrogen peroxide. This is a particularly unexpected finding, as Amaranth Red is used as an indicator in a commercially available powder-based detergent called Virkon, a product produced and marketed by Antec Ltd. In the case of Virkon, as long as the red colouration due to Amaranth is present, the Virkon solution is still actively biocidal. According to the Virkon product brochure, VIRKON 1% solutions are stable for 7 days but should be discarded when the pink colour fades.
(47) Virkon is comprised of a mixture of potassium monoperoxysulfate, sodium chloride, sulfamic acid, plus other ingredients such as surfactants, perfumes, as well as Amaranth. According to a background document produced by Antec, on dissolution in water, the Virkon powder mix undergoes the Haber-Willstatter Reaction, producing a mix of biocidal species including the potassium monoperoxysulfate, chlorine, N-chlorosulfamic acid, hypochlorous acid. The document goes on to state that Virkon contains a pink dye (amaranth colour, EEC No. 123). In addition to being aesthetically pleasing, this serves a very practical purposeit indicates whether the VIRKON solution is active. In its oxidised form, it is pink but when the solution starts to lose its activity it reverts to its colourless reduced form. VIRKON solutions must always be replaced if the colour starts to fade. In other words, the pink-red colouration due to Amaranth is present whilst the active oxidatively biocidal species are also present, with the colour only fading as the oxidative biocides become depleted.
(48) Conversely, in '633, colour depletion of the disinfectant solution indicates that an effective biocidal concentration of peracetic acid has been achieved.
(49) Substantially Bleach-Stable Dyes
(50) The second dye which may optionally be included in the composition of '633, as used in the present invention, is a substantially bleach-stable dye. It is recognised that peracetic acid will be capable of bleaching most dyes, and therefore reference to a substantially bleach-stable dye is to be taken as meaning that the dye is capable of imparting colour to the peracetic acid/hydrogen peroxide solution for at least 2 hours, preferably about 4 to 6 hours, at room temperature.
(51) Examples of substantially bleach-stable dyes which may be used in the composition of '633 and in the present invention include, but are not limited to, Acid Blue 182, Acid Blue 80, Direct Blue 86, Acid Green 25 (C.I. 61570) and combinations thereof.
(52) In a particularly preferred embodiment of the composition of '633, as used in the present invention, the first dye is Amaranth Red (C.I. 16185) and the second dye is C.I. Acid Blue 182. In this embodiment, the colour of the solution upon dissolution of the composition is red, generated by the Amaranth. The red colour discharges at around 5-7 minutes, at which time the peracetic acid is at a biocidally effective concentration, leaving a blue colour, generated by the Acid Blue 182. The blue colour is aesthetically pleasing, and has the added benefit of making the solution more visible when disinfecting a surface or object.
(53) Wetting Agent
(54) When the composition of '633, as used in the present invention, is in a powder formulation, a wetting agent may be included in the composition to facilitate dispersion of the acetyl source into solution on initial dilution, thus assisting in its dissolution. The wetting agent is preferably comprised of a solid surfactant capable of lowering the surface tension of the solvent, preferably water, thus allowing the acetyl source to wet and disperse. Preferably, the acetyl source is TAED and, in the absence of a wetting agent, a highly micronized grade of TAED such as B675 will tend to float on the surface of the solvent, and thus be slow to dissolve, resulting in slow production of peracetic acid. Examples of suitable wetting agents which may be used in the composition of the invention include, but are not limited to, sodium dodececyl sulphate, sodium alkylbenzenesulphonate, Pluronic PE6800, Hyamine 1620 etc, and combinations thereof.
(55) pH Buffering Agents
(56) Optionally, a pH buffer may be included in the composition of '633, as used in the present invention, to reduce the variation of pH with time. Since the formation of peracetic acid from the acetyl source, preferably TAED, requires the pH to be at, or above, the pKa of peracetic acid (8.2), the pH of the solution should be buffered between 8.00 and 9.00, preferably between 8.00 and 8.40. Suitable pH buffers which may be included in the composition of the invention include, but are not limited to, phosphate, borate, bicarbonate, TAPS (3-{[tris(hydroxymethyl)methyl]amino}propanesulfonic acid), Bicine (N,N-bis(2-hydroxyethyl)glycine), Tris (tris(hydroxymethyl)methylamine), Tricine (N-tris(hydroxymethyl)methylglycine) and combinations thereof.
(57) Sequestering Agents
(58) Optionally, the composition of '633, as used in the present invention, may include ingredients capable of complexing metal ions such as calcium and magnesium, thus negating any adverse effect from the use of hard water, as well as metal ions such as iron, manganese, copper etc which are capable of catalysing the decomposition of peroxides, and which also may be present in tap water. Examples of chelating and sequestering agents which may be used in the composition of the invention include, but are not limited to, sodium citrate, citric acid, phosphoric acid, sodium tripolyphosphate, EDTA, NTA, etc and combinations thereof.
(59) Flow Modifiers
(60) A flow modifier may be added to improve the flow characteristics of the composition of '633, as used in the present invention, when in a powder formulation. This is particularly useful if the powder is intended for supply in a unidose package (eg an individual sachet or water soluble pouch), as good powder flow will allow accurate dosing of the blended powder into the individual packs. Examples of powder flow modifiers which may be used in the composition of '633 and in the present invention include, but are not limited to, fumed silica, precipitated silica, micronized polyethylene glycol 6000, micronized lactose, talc, magnesium stearate etc, and combinations thereof.
(61) In a preferred example, the flow modifier is a hydrophilic fumed silica, for example Aerosil 200 (Evonik Industries).
(62) It may also possible to achieve good flow improvements using a precipitated silica such as Tixosil 38, although the precipitated silica grades are less preferred as they produce a strong haze in the final disinfectant solution, by virtue of the larger particle size of the precipitated form over the fumed form.
(63) Perfumes
(64) Optionally, the composition of '633, as used in the present invention, may also contain perfumes to mask the odour of peracetic acid. The perfume used should preferably be stable to hydrogen peroxide and peracetic acid.
(65) In a preferred embodiment of the composition of '633 and as used in the process of the present invention, the acetyl donor is TAED, the hydrogen peroxide source is sodium percarbonate, the first dye is Amaranth Red, and the composition is in a powder formulation, which is dissolved in water. On initial mixing of the powder formulation with tap water, at ambient temperatures, a deep red cloudy solution is formed by the rapid dissolution of the Amaranth Red dye and the suspension of undissolved TAED. Over the course of approximately 5-10 minutes, the TAED dissolves into the water, and the red colouration is discharged as peracetic acid is generated by the reaction of the TAED with hydrogen peroxide produced by dissolution of the sodium percarbonate. After about 7-10 minutes, the solution will be clear, and all of the red colouration discharged.
(66) In another preferred embodiment, a second dye that is substantially bleach-stable may also be included in the composition of '633, as used in the process of the present invention. Preferably the substantially bleach-stable dye bleaches over the course of 4-6 hours, along with the Amaranth. A preferred second dye, which is slowly bleached, is C.I. Acid Blue 182.
EXAMPLES
Example 1
(67) Dye premix: A mixture of 78.00 g of TAED B675 (Warwick Chemicals), 17.00 g Amaranth dye and 5.00 g of C.I. Acid Blue 182 dye were mixed and ground together using a pestle and mortar to give a homogenous brownish powder. Once mixed, the dye premix blend was stored in a well-sealed container prior to use.
(68) 54.55 g of TAED B675, 1.00 g of the dye-TAED premix, 1.32 g of powdered sodium dodecyl sulphate and 0.60 g Aerosil 200 (a hydrophilic fumed silica available from Evonik) were mixed together, and passed through a 125 micron sieve to remove and break up any aggregated material. After sieving, mixing was continued to produce a homogenous powder.
(69) To the sieved material was added 0.49 g tetrasodium EDTA, 28.00 g of anhydrous citric acid, 99.32 g of sodium percarbonate, 15.50 g of sodium tripolyphosphate and 1.80 g of anhydrous monosodium phosphate. The powders were then mixed thoroughly to produce a homogenous, free-flowing powder. The full composition of the powder blend is shown in Table 2, along with the function of each ingredient.
(70) It was found that it was only necessary to add 1% of the TAED weight of the Aerosil 200 to the powder blend. This equates to 0.3% of the overall blend weight. At this level, the Aerosil will produce only a very slight haze in the final disinfectant solution.
(71) TABLE-US-00002 TABLE 2 Ingredient % w/w Function Sodium percarbonate 49.03 Hydrogen peroxide source TAED B675 27.31 Acetyl donor Citric acid 13.82 Acidifier Sodium tripolyphosphate 7.65 Sequestrant and pH modifier Monosodium phosphate 0.89 pH modifier Sodium dodecyl sulfate 0.65 Surfactant and wetting agent Aerosil 200 0.30 Flow modifier Tetrasodium EDTA 0.24 Chelating agent Amaranth 0.084 PAA bleachable Colourant Acid Blue 182 0.025 PAA stable Colourant
(72) A solution of the disinfectant was prepared by dissolving 7.50 g of the powder blend into 500 ml of artificial hard water containing 340 ppm CaCO.sub.3 (prepared as described in SOP Number: MB-22-00: Standard Operating Procedure for Disinfectant Sample Preparation, published by the US Environmental Protection Agency Office of
(73) Pesticide Programs, and hereafter referred to as AOAC Hard Water). The solution was stirred at room temperature. The red colour due to the Amaranth was observed to be discharged at around 5-7 minutes, leaving a blue solution.
(74) 10 ml aliquots taken at regular intervals after 10 minutes, and the pH were also recorded. The aliquots were titrated to determine hydrogen peroxide and peracetic acid concentration.
(75) As may be seen in
(76) Interestingly, if the concentration of powder dissolved into the water is increased, whilst the maximum peracetic acid concentration increases as expected, it was also observed that its decomposition rate was also increased (see
Example 2
(77) 4 disinfectant solutions in AOAC Hard Water were prepared using differing concentrations of the powder blend from Example 1, and stirred for 20 minutes. Aliquots were taken and titrated for hydrogen peroxide and peracetic acid concentration, whilst further aliquots were inoculated with suspensions of both vegetative and spore forms of Clostridium sporogenes (ATCC 3584), in the presence of 5% horse serum. The organisms were exposed for 3, 5 and 10 minutes. Each sample was tested in triplicate, and each sample gave greater than a 6 log reduction in viable organisms at each time point.
(78) Table 3 shows the concentration of the solutions used, the concentrations of both hydrogen peroxide and peracetic acid, along with the log reductions recorded.
(79) TABLE-US-00003 TABLE 3 Concentrations (ppm) Contact Time H2O2 PAA 3 minute 5 minute 10 minute Vegetative cells Sample 1 (20 g/L) 1382 2964 >6 log >6 log >6 log Sample 2 1330 2550 >6 log >6 log >6 log (16 g/L) Sample 3 980 1980 >6 log >6 log >6 log (12 g/L) Sample 4 (8 g/L) 569 1349 >6 log >6 log >6 log Bacterial spores Sample 1 (20 g/L) 1382 2964 >6 log >6 log >6 log Sample 2 1330 2550 >6 log >6 log >6 log (16 g/L) Sample 3 980 1980 >6 log >6 log >6 log (12 g/L) Sample 4 (8 g/L) 569 1349 >6 log >6 log >6 log
Example 3
(80) 7.50 g of the powder blend from Example 1 was taken, and added to 500 ml of tap water, and stirred at room temperature. The time the red colour was discharged was noted, and a 5 ml aliquot taken and titrated. A further 5 ml aliquot was removed and titrated after 20 minutes.
(81) As can be seen in Table 4, the colour due to Amaranth was being removed between 7 and 8 minutes, with the peracetic acid content at this time being between 0.14 and 0.16%.
(82) TABLE-US-00004 TABLE 4 Time for Dye bleach Amaranth dye time 20 min Sample bleaching HP PAA HP PAA 1 8 min 0.13% 0.14% 0.11% 0.21% 2 7 min 50 sec 0.141 0.155 0.124 0.22% 3 7 min 0.13% 0.16% 0.11% 0.23%
(83) As can be seen in Table 3, solutions containing at least 1.35% (1349 ppm) peracetic acid exhibit sporicidal activity, thus it may be safely assumed that once the red colouration due to Amaranth has been discharged, the peracetic acid content will be above this sporicidally active concentration.
Example 4
(84) Differing weights of the powder blend from Example 1 were taken, and added to 500 ml of tap water, and stirred at room temperature. The time the red colour was discharged for each solution is shown in Table 5.
(85) TABLE-US-00005 TABLE 5 Weight of powder Weight of AOAC Hard Time taken for discharge of (g) water (g) red colour (minutes) 6.00 500 7.5 7.02 500.02 7 8.02 500.01 6.5 9.00 500 6 10.03 499.99 5.25
Example 5
(86) A quantity of the powder blend from Example 1 was taken, and packaged into individual sachets prepared from heat sealed PVA water soluble film. The sachets were prepared by heat sealing two sheets of 50 micron thick PVA film (width 4.65 cm, length 8 cm), together to form an envelope, dispensing approximately 8.2 g powder into each envelope and then sealing the open side to give the finished filled sachet.
(87) A single sachet was then taken and added to a stirred quantity of tap water (500 ml). The sachet was observed to wrinkle in the water, and then to burst open, releasing the contained powder into the water to give a deep red solution. After approximately 8 minutes, the red colour was discharged, leaving a pale blue solution with a faint odour of peracetic acid. Aliquots of the resultant solution were taken at 10 and 20 minutes and titrated for hydrogen peroxide and peracetic acid content.
(88) Assessment of an initial production run to produce sachets is shown in Table 6, and Table 7 shows the result of assessing peracetic acid generation from several sample sachets dissolved into 500 ml tap water.
(89) TABLE-US-00006 TABLE 6 mean sachet weight 8.29 Standard deviation 0.514 % RSD 6.2 Maximum weight 9.59 Minimum weight 7.48 sample size 70
(90) TABLE-US-00007 TABLE 7 sachet 10 minutes 20 minutes wt (g) pH H2O2 % PAA % pH H2O2 % PAA % 1 8.3 8.39 0.146 0.145 8.26 0.121 0.223 2 8.48 8.12 0.138 0.171 8.07 0.127 0.215 3 8.74 8.54 0.163 0.175 8.23 0.127 0.229 4 7.78 8.23 0.125 0.175 8.16 0.107 0.208 5 8.16 8.2 0.14 0.109 8.1 0.124 0.2 6 9.1 8.33 0.161 0.214 8.23 0.148 0.198 7 7.67 8.21 0.133 0.192 8.12 0.116 0.16 8 8.11 8.12 0.132 0.078 7.99 0.118 0.205 mean 8.29 8.27 0.14 0.16 8.15 0.12 0.20
Example 6
(91) A quantity of the powder blend according to Example 1 was taken, and packaged into individual sachets prepared from heat sealed PET-paper-Aluminium-PP laminate. The sachets were prepared by heat sealing a sheet of laminate 6 cm wide to form a cylindrical tube, and then sealing across the tube to form a stick, which was then dosed with the powder blend via an auger doser. The open end of the filled tube was then sealed to give a stick pack.
(92) The mean gross weight of each stick pack was found to be 8.88 g, with a standard deviation of 0.27 (see Table 8). The packaging material was found to weigh 0.88 g, thus giving a mean net weight for the powder of 8.00 g.
(93) TABLE-US-00008 TABLE 8 mean sachet weight 8.88 Standard deviation 0.27 % RSD 3.06 Maximum weight 9.66 Minimum weight 8.13 sample size 500
(94) To demonstrate homogeneity of blending, sample sachets were taken from various parts of a production run and added to 500 ml of tap water. The hydrogen peroxide and the peracetic acid content at 10, 20 and 30 minutes for each solution were then determined.
(95) As can be seen in
(96) This example demonstrates the utility of the dye system as an indicator for the presence of an effective biocidal concentration of peracetic acid.
(97) This was further illustrated by adding 7.50 g of the powder blend according to Table 9 to 500 ml of AOAC Hard water and testing its biocidal activity against surface bound micro-organisms in an AOAC Hard Surface Carrier Test 991.47, 48 and 49, conducted in the presence of 5% horse serum against Pseudomonas aeruginosa, Staphylococcus aureus and Salmonella choleraesuis. The test methodology was modified to use a 5 minute contact time rather than the prescribed 10 minute contact time.
(98) TABLE-US-00009 TABLE 9 No. No. carriers No. Carriers Carriers Test organism tested Negative Positive Result Pseudomonas aeruginosa 60 57 3 PASS ATCC 15442 Staphylococcus aureus 60 58 2 PASS ATCC 6538 Salmonella choleraesuis 60 60 0 PASS ATCC 10708
(99) The powder formulation can also be modified for the production of tablets capable of generating peracetic acid on dissolution into water. Preferably, a means to facilitate the disintegration of the tablet is incorporated into the tablet formulation. This also assists the slower dissolution of the tablet due to the compression required to generate the tablet.
(100) Poly-NVP based disintegrants such as Disintex 200 (ISP Technologies Inc) were found to be impractical for use, as the cross-linked polymer adsorbed the dyes strongly, and thus gave highly coloured particulate material in the final solution. A preferred means of disintegrating the tablet is to include additional sodium carbonate into the formulation, along with additional acidifying agent. In a more preferred embodiment, sulfamic acid is used as the acidifying agent as this lacks a pKa above 2. If citric acid is used as an acidifying agent in the tablet formulation, then gas formation, hence tablet disintegration, is slowed down once the solution reached a pH of around 6 due to the third pKa of citric acid.
Example 7
(101) A powder blend according to Table 10 was produced by mixing the ingredients together to produce a homogenous mix. In order to achieve adequate tablet formulation, the mixture was not sieved, and care was taken not to reduce the particle size of the soda ash, sodium percarbonate and the sulfamic acid.
(102) TABLE-US-00010 TABLE 10 TAED 13.54 sodium 37.15 percarbonate sulfamic acid 30.82 Dense soda ash 18.06 Sodium dodecyl 0.23 sulfate Tetrasodium EDTA 0.15 Amaranth 0.038 Cl Acid Blue 182 0.011
(103) Once blended, the material was tableted using a single punch tablet press, fitted with a 20 mm die set to give tablets with a mean weight of 3.72 g. The mean thickness of the tablets was 9.1 mm, with a thickness to weight ratio of 0.41.
(104) Two tablets, with a combined weight of 8.34 g were then dissolved in 200 ml of tap water. After stirring for 25 minutes at room temperature, three 10 ml aliquots were removed and titrated. The mean concentrations for hydrogen peroxide and peracetic acid were found to be 0.293% and 0.258% respectively.
(105) An additional tablet was taken and dissolved into AOAC Hard water, and then tested for antimicrobial activity against Clostridium difficile in the presence of 5% horse serum at 20? C., using the method of BS EN 1276 (1997). The resultant observed log reductions are shown in Table 11.
(106) TABLE-US-00011 TABLE 11 Test organism: Contact time Clostridium difficile (temperature = 20? C. ATCC70992 1 5 10 Log reduction 2.77 >5.86 >5.86 (initial inoculum level 4.8 ? 10.sup.6
Example 8: Production of Model Dry Surface Biofilm Samples
(107) Dry surface biofilm was produced in the surfaces of coupons following the method described by Almatroudi et al. in Reference 4.
(108) Staphylococcus aureus ATCC 25923 biofilm was grown on 24 removable, sterile Pyrex coupons in an intensively cleaned, brushed and steam sterilised (121? C. for 20 min) CDC biofilm reactor (BioSurface Technologies Corp, Bozeman, USA).
(109) Semi-dehydrated biofilm was grown over 12 days with cycles of batch growth during which time 5% tryptone soya broth (TSB) was supplied alternating with prolonged dehydration phases at room temperature (22-25? C.) as described in Table 12, with the TSB being removed from the Biofilm Reactor at the end of each batch phase.
(110) The biofilm generator was located in an air-conditioned laboratory and filter-sterilised room air (average relative humidity 66%) was pumped across the media surface at an airflow rate of 3 l/min using an aquarium air pump.
(111) Biofilm development was initiated by inoculation of about 10.sup.8 colony forming units (CFU) of S. aureus at the beginning of the first batch phase. During batch phases, all biofilms were grown in 5% TSB at 35? C. and subjected to shear by baffle rotation at 130 rpm/min producing turbulent flow.
(112) TABLE-US-00012 TABLE 12 Stage Culture conditions Cumulative time 1 48 h batch phase in 5% TSB followed by 48 h 96 hr dehydration 2 6 h batch phase in 5% TSB followed by 66 h 168 hr dehydration 3 6 h batch phase in 5% TSB followed by 42 h 216 hr dehydration 4 6 h batch phase in 5% TSB followed by 66 h 288 hr dehydration
(113) Following growth of the biofilm, the rods holding the biofilm coated coupons were removed from the generator, and placed in 1 litre of phosphate buffered saline (PBS) for 5 minutes. The three coupons on each rod were then removed, and washed an additional two times by placing them in to 50 ml PBS before being placed in individual sterile Bijou containers. The number of CFU per coupon was determined by sonication of a randomly selected coupon in an ultrasonic bath (Soniclean, JMR, Australia) for 5 min and vigorous shaking for 2 min in 4 ml of media followed by sequential 10-fold dilution and plate count.
Example 9: Peracetic (PAA) Based Disinfectant
(114) A sachet containing 8.5 g of a disinfectant powder composition similar to Example 1. The disinfectant powder comprised a blend of a hydrogen peroxide source (sodium percarbonate) and an acetyl source (tetraacetylethylenediamine (TAED)), along with acidifying agents (citric acid) and sequestrants (monosodium phosphate, sodium tripolyphosphate), along with a peracetic acid bleachable dye (amaranth). The formulation used is given in Table 13.
(115) TABLE-US-00013 TABLE 13 Ingredient % w/w Function Sodium percarbonate 49.18 Hydrogen peroxide donor TAED B675 27.39 Acetyl donor Citric acid 13.86 Acidifier Sodium tripolyphosphate 7.67 Sequestrant Sodium phosphate 0.89 pH modifier Sodium dodecyl sulfate 0.65 Wetting agent Tetrasodium EDTA 0.24 Chelating agent Amaranth 0.08 PAA bleachable colourant Acid Blue 182 0.03 PAA stable colourant
(116) The sachet was added to 500 ml water and stirred at room temperature for 10-15 minutes, after which time the colouration provided by the peracetic acid bleachable dye was discharged. At this point the solution will contain between 1500 and 2000 ppm peracetic acid, along with about 1000-1300 ppm hydrogen peroxide. The resultant solution was found to be active against a range of bacteria, viruses, spores and fungi for approximately 8 hours after dissolution.
Example 10: Initial Screening Study Using TOC to Assess Removal of Dry Surface Biofilm
(117) In an initial screening study, a range of cleaning products were assessed for their dry surface biofilm removing efficacy by assessment of Total Organic Carbon (TOC). The products assessed, and their in-use concentrations are shown in Table 14.
(118) TABLE-US-00014 TABLE 14 Detergent Supplier Dilution Fabrisan Whiteley Corporation Used undiluted Matrix Whiteley Corporation 1:25 Zip Strip Whiteley Corporation 1:6 Phensol Whiteley Corporation 1:50 Example 9 Whiteley Corporation 17 g per litre Sodium hypochlorite Fronine Pty Ltd, 1000 ppm available chlorine 1M Sodium hydroxide Chem Supply Ltd Used undiluted solution Negative control (water) Used undiluted
(119) Fabrisan is marketed as a carpet spotter. Its ingredients include sodium citrate, sodium dodecyl sulfate, and Tea Tree Oil. The formulation is according to Example 3 of U.S. Pat. No. 5,610,189
(120) Matrix is marketed as a wet surface biofilm remover. The formulation is according to Australian patent no. AU200127559962, and its efficacy against normal (wet) biofilm has been described by Vickery et al (Reference 8 and Reference 9), Ren et al (Reference 10) and Fang et al, (Reference 11). The Ren and the Fang references were performed using Intercept, which has an identical formulation to Matrix and is manufactured under license from Whiteley Corporation by Medivators Inc.
(121) Zip Strip is a floor stripper intended to remove polymeric sealants form vinyl floors. The formulation comprises a highly alkaline solution of surfactants, butyl glycol, and ethanolamine.
(122) Phensol is a phenolic disinfectant comprising a blend of o-phenylphenol and benzyl chlorophenol with the sodium salt of a (C10-16) Alkylbenzenesulfonic acid.
(123) Each cleaning solution was diluted according to the label directions, as shown in Table 14.
(124) A 12 day dry surface biofilm was grown on Pyrex glass coupons as described in Example 8. Three coupons, coated in dry surface biofilm were then placed into 25 ml of each test product solution. Three coupons were also placed in 25 ml of MilliQ water to serve as a negative control. A 1M solution of sodium hydroxide was used as a positive control.
(125) Each sample was prepared and tested in duplicate.
(126) Blank coupons, in which fresh, clean coupons were exposed to the test products were also produced, in order to assess any adherence of organic materials (such as surfactants) to the coupons, were also analysed.
(127) After exposure to the test product solution for the required time, the coupons were rinsed twice in 25 ml Milli-Q water. The Total Organic Carbon on each coupon was then measured using a Shimadzu-5000A TOC analyser. The TOC resulting from any residual biofilm left after cleaning was calculated by subtracting the TOC found on the blank coupons from the TOC resulting from the residual carbon left on the biofilm coated coupons after cleaning.
(128) The results are given in Table 15. The percentage TOC remaining due to the biofilm shown in parentheses were calculated relative to the negative control (Milli-Q water).
(129) TABLE-US-00015 TABLE 15 TOC (?g) Blank Coupons with TOC due to coupons Biofilm biofilm % Reduction Fabrisan 1.13 4.77 3.64 51 Matrix 0.82 6.87 6.05 18 Zip Strip 1.16 5.33 4.17 43 Phensol 0.76 3.45 2.69 64 Example 9 0 0.47 0.47 94 Chlorine 100 ppm 0.34 1.87 1.53 79 1M NaOH 0.17 0.16 ?0.01 100 Negative control 0.06 7.43 7.37 0
(130) From this screening study, it can be clearly seen that products demonstrated to be efficacious in the removal of normal, wet surface biofilm (ie Matrix) do not show the same degree of efficacy against dry surface biofilm. Apart from the 1M sodium hydroxide solution, the two most efficacious cleaning solutions were Example 9 and Chlorine.
Example 11
(131) The efficacy of removal of wet biofilm was assessed for both Example 9 and Matrix, a product demonstrated to remove wet surface biofilm.
(132) A wet Staphylococcus aureus biofilm was grown on plastic tiles supported on modified rods in a CDC Biofilm Reactor over 48 hours, following the methodology of Goeres et al (Reference 12).
(133) The plastic tiles were then placed into Falcon tubes containing Matrix (at a 1:25 dilution in water), Example 9 (17 g/L in water) and Milli-Q water. The tiles were left immersed in the cleaning solutions for 10 minutes. After 10 minutes the tiles were removed, washed twice with Milli-Q water, and then placed into 40 ml of a 0.3% solution of Crystal Violet, (a stain for biofilm). The tiles were then stood for 90 minutes in the Crystal Violet solution. After 90 minutes, the tiles were removed, washed for 1 minute three times in Milli-Q water. The washed tiles were then scraped, and eluted with 5 ml of 95% ethanol into a 28 ml vial, which was then closed and stood overnight to elute the adsorbed Crystal Violet. The absorbance of the solutions were then read via a spectrophotometer.
(134) TABLE-US-00016 TABLE 16 Cleaning product Absorbance Example 9 0.128 Matrix 0.120 Milli-Q water 0.191
(135) As can be seen in Table 16, Matrix removed most biofilm from the tile as shown by the lower absorbance due to Crystal Violet.
Example 12
(136) The efficacy of protein removal of Example 9 and Matrix was demonstrated as follows:
(137) 12 day biofilm was grown on PET coupons following the methodology of Example 8. The rods containing the biofilm coated coupons were then removed and any loosely bound biofilm washed off with Milli-Q water as described in Example 8.
(138) One rod holding three dry surface biofilm coated coupons was then placed into 30 ml of a solution of Example 9 (17 g/litre) for 10 minutes. A second rod was placed into 30 ml of a solution of Matrix (1:50 dilution), and a third rod placed into 30 ml Milli-Q water to serve as a positive control. An additional rod, holding 3 uncoated coupons was sterilized and used as a negative control.
(139) After 10 minutes, each rod was placed into 30 ml of 1M sodium hydroxide solution to elute off all remaining protein. Aliquots from each solution were then taken and tested for protein using a Bicinchroninic Acid (BCA) assay, using a micro BCA test kit (Sigma Aldrich).
(140) In order to perform the BCA assay, a series of standard solutions of bovine serum albumin were prepared to produce a standard curve. 1 ml of each of the standard BCA solutions, along with 1 ml aliquots taken from the cleaning solutions were all then treated with 1 ml of a working BCA solution prepared by mixing 50 ml Bicinchononic acid (Sigma Aldrich cat. B9643) into a beaker, and adding 1 ml of 4% copper (II) sulfate solution (Sigma Aldrich cat. No. C2284). The samples were then incubated for 60 minutes at 60? C., and the absorbance at 562 nm read using a spectrophotometer (see Table 17).
(141) TABLE-US-00017 TABLE 17 Derived Percentage concentration reduction of Sample Absorbance (ppm) protein Concn. BSA (ppm) 0 0 0.5 0.027 1 0.042 2.5 0.085 5 0.144 10 0.32 20 0.682 40 1.209 Test samples Example 9 0.249 0.249 66.4 Matrix 0.362 0.362 50.5 Water 0.721 0.721 0.0
(142) As can be seen, Example 9 gives a significantly higher reduction of protein than Matrix when tested against 12 day dry surface biofilm.
Example 13
(143) The efficacy of protein removal from coupons coated in 12 day dry surface biofilm using Example 9, 1000 ppm sodium hypochlorite solution and Chlorclean, (a sodium diisocyanurate (SDIC) tablet formulated with adipic acid and a sodium toluenesulfonate and marketed as a 2-in-1 Hospital Grade Disinfectant with detergent action by Helix Solutions (Canning Vale South, Western Australia) were assessed as described in Example 11. Both chlorine solutions were shown to give 1000 ppm, available chlorine. In this test a 10 minute contact time was used. Percentage reductions were calculated from the positive control (Milli-Q water).
(144) As can be seen in Table 18, Example 9 gives the highest protein reduction. Chlorclean, a formulated SDIC tablet marketed as a 2-in-1 cleaning/disinfecting product was also observed to be more efficacious than sodium hypochlorite solution.
(145) TABLE-US-00018 TABLE 18 Percentage protein Detergents tested reduction 1000 ppm Chlorine (sodium hypochlorite) 11.50 1000 ppm Chlorine (Chlorclean tablet) 39.26 Example 9 (17 g/L) 63.65
Example 14
(146) In order to determine whether the presence of detergent moieties within the cleaning products were responsible for the difference in performance between sodium hypochlorite and the proprietary Chlorclean tablet, the methodology of example 13 was repeated, only with the sodium hypochlorite solution being replaced with a solution of sodium diisocyanurate, giving 1000 ppm available chlorine.
(147) TABLE-US-00019 TABLE 19 Detergents tested Percentage reduction 1000 ppm Chlorine (SDIC) 17.65 1000 ppm Chlorine (Chlorclean tablet) 13.12 Example 9 (17 g/L) 64.69
(148) Of note here is the marked reduction in efficacy of Chlorclean with the shorter contact time. The protein reduction observed with the Example 9 was observed to be substantially the same despite the difference in contact times.
Example 15
(149) The bacterial reductions obtained from a 12 day dry surface biofilm were assessed under clean conditions using Example 9, Chlorclean tablets and a generic SDIC tablet
(150) Each test product was dissolved in water.
(151) Coupons coated in 12-day dry surface biofilm were produced as per Example 8. 2 ml of each test solution, followed by 2 ml of water were added to the wells in a tissue culture plate.
(152) After a 5 minute contact time, coupons were removed from the disinfectant solutions, rinsed twice using 30 ml phosphate buffered saline for 5 seconds, and then placed into 5 ml tubes containing 2 ml of a neutralizer solution comprising 6% Tween 80 plus 1% sodium thiosulfate plus 5% bovine serum plus 10% Bovine Serum Albumin.
(153) The tubes were sonicated for 20 minutes and then vortexed for 2 minutes. Serial 10-fold dilutions were then made and 100 ul of neat, 10.sup.?1, 10.sup.?2, 10.sup.?3 and 10.sup.?4 dilutions were plated on Horse Blood Agar plates. The plates were incubated at 37? C. overnight and then enumerated.
(154) Control coupons, not exposed to disinfectant were similarly worked up to allow the log reductions to be calculated
(155) As can be seen in Table 20, the disinfectant according to Example 9 gave the largest log reduction of biofilm.
(156) TABLE-US-00020 TABLE 20 Log reduction Neutraliser control Example 9 6.556 0.0437 Chlorclean (1000 ppm Cl) 4.411 0.017 SDIC (1000 ppm Cl) 6.55 0.045
Example 16
(157) The bacterial reductions obtained from a 12 day dry surface biofilm were assessed under dirty conditions using Example 9, Chlorclean tablets and a generic SDIC tablet. Each test product was dissolved in artificial hard water containing 340 ppm CaCO.sub.3 to which was added 5% Bovine Calf Serum.
(158) Coupons coated in 12-day dry surface biofilm were produced as per Example 8. 2 ml of each test solution, followed by 2 ml of hard water to which was added 5% bovine calf serum were added to the wells in a tissue culture plate.
(159) After a 5 minute contact time, coupons were removed from the disinfectant solutions, rinsed twice using 30 ml phosphate buffered saline for 5 seconds, and then placed into 5 ml tubes containing 2 ml of a neutralizer solution comprising 6% Tween 80 plus 1% sodium thiosulfate plus 5% bovine serum plus 10% Bovine Serum Albumin.
(160) The tubes were sonicated for 20 minutes and then vortexed for 2 minutes. Serial 10-fold dilutions were then made and 100 ul of neat, 10.sup.?1, 10.sup.?2, 10.sup.?3 and 10.sup.?4 dilutions were plated on Horse Blood Agar plates. The plates were incubated at 37? C. overnight and then enumerated.
(161) Control coupons, not exposed to disinfectant were similarly worked up to allow the log reductions to be calculated.
(162) As can be seen in Table 21, the disinfectant according to Example 9 gave a log reduction essentially equivalent to that seen under clean conditions (see Table 20). It was also observed that both chlorine tablets gave essentially no log reduction of bacteria, suggesting complete neutralisation of the chlorine disinfectant by the proteinaceous soil.
(163) TABLE-US-00021 TABLE 21 Log reduction Neutraliser control Example 9 6.531 0.010 Chlorclean (1000 ppm Cl) 0.002 0.005 SDIC (1000 ppm Cl) 0.007 0.018
Example 17
(164) In this example, the disinfectant according to Example 9 was tested against planktonic S. aureus, and compared to two commercially obtained oxidising disinfectants, Chlorclean and Oxivir Tb (Diversey Australia Pty Ltd, Smithfield, NSW, Australia), a ready to use solution comprising 0.5% hydrogen peroxide, formulated with other proprietary ingredients.
(165) Alongside these commercial products some generic equivalents were also tested. These comprised Proxitane (Solvay Interox, Botany, NSW, Australia), an equilibrium solution of hydrogen peroxide, acetic acid and Peracetic acid containing 27% hydrogen peroxide, 7.5% acetic acid and 5% of peracetic acid, an unformulated SDIC tablet (Redox Chemicals, Minto, NSW Australia) that released 1000 ppm chlorine on dissolution in 10 litres of water, and a 6% solution of hydrogen peroxide (Gold Cross, Biotech Pharmaceuticals Pty Ltd, Laverton North, Victoria, Australia). These generic products were selected to try to match the active ingredients in the formulated product, thus assess the role of the product formulation.
(166) Where applicable, the disinfectant products were diluted using artificial hard water prepared by dissolving 0.304 g anhydrous CaCl.sub.2) and 0.065 g anhydrous MgCl.sub.2 in distilled water to make one litre of hard water.
(167) Table 22 shows the products tested, and the concentrations of active materials in the test samples.
(168) TABLE-US-00022 TABLE 22 Concentration of active Product Sample preparation ingredients Example 9 8.5 g powder dissolved in 1100 ppm hydrogen peroxide 500 ml hard water 2200 ppm PAA Chlorclean 1 tablet dissolved in 1 litre 1000 ppm chlorine hard water Oxivir Tb Used undiluted 0.5% (5000 ppm) Accelerated? hydrogen peroxide Generic equivalents Proxitane 4 ml Proxitane diluted to 10,080 ppm hydrogen 100 ml with hard water peroxide 2,200 ppm PAA 20 g SDIC 1 tablet dissolved in 10 1000 ppm chlorine tablets litres hard water 6% hydrogen 10 ml diluted to 100 ml 0.6% (6000 ppm) hydrogen peroxide with hard water peroxide
(169) Disinfectant efficacy in the absence of soil was tested by mixing 1 ml of test disinfectant with 1 ml of hard water and immediately adding 10 ?l of Tryptone Soy Broth (TSB) containing approximately 10.sup.9 planktonic bacteria for 5 minutes contact time. 1 ml neutralizer (1% Na-thiosulphate, 6% Tween 80, 5% BCS and 10% BSA in PBS) was then added.
(170) Disinfectant efficacy in the presence of soil was tested by mixing 1 ml of test disinfectant with 1 ml of 5% bovine calf serum in hard water and immediately adding 10 ?l of Tryptone Soy Broth (TSB) containing approximately 10.sup.9 planktonic bacteria for 5 minutes contact time for 5 minutes contact time. prior to the addition of 1 ml of neutralizer. 1 ml neutralizer (1% Na-thiosulphate, 6% Tween 80, 5% BCS and 10% BSA in PBS) was then added
(171) Testing of these disinfectant systems against planktonic S. aureus showed that each one was capable of achieving a 7 log.sub.10 reduction in the absence of organic soil. However, when tested under dirty conditions, only Example 9 retained its full efficacy.
(172) As can be seen in
Example 18
(173) The efficacy of the test disinfectants shown in Table 22 to kill the organisms within a dry surface biofilm of S. aureus was determined in the presence and absence of biological soil. Each condition was tested with five replicates for determining residual bacterial number (colony forming unitsCFU) using a 5-minute contact time.
(174) Disinfectant efficacy in the absence of soil was tested by mixing 1 ml of test disinfectant with 1 ml of hard water and immediately adding a biofilm coated coupon for 5 minutes contact time. 1 ml neutralizer (1% Na-thiosulphate, 6% Tween 80, 5% BCS and 10% BSA in PBS) was then added.
(175) Disinfectant efficacy in the presence of soil was tested by mixing 1 ml of test disinfectant with 1 ml of 5% bovine calf serum in hard water and immediately adding a biofilm coated coupon for 5 minutes contact time prior to the addition of 1 ml of neutralizer.
(176) Positive (biofilm covered coupons) and negative (clean sterile coupons) control were subjected to the same treatments as described above but test disinfectants were replaced with hard water. Confirmation that disinfectant activity was completely inactivated by the addition of 1 ml of neutraliser was tested by adding 1 ml of neutraliser to test mixture (1 ml disinfectant plus 1 ml of either soil or hard water), immediately adding a biofilm covered coupon and reacting for 5 minutes (results not shown).
(177) Determination of residual biofilm viability was determined by subjecting control and test coupons to sonication at 80 kHz for 20 minutes prior to serial 10-fold dilution and overnight plate culture at 37? C. and CFU determination.
(178) Results
(179) Positive control coupons had a mean of 2.6?10.sup.6CFU/coupon.
(180) In the absence of biological soil, and with a five minutes contact time, example 9 was observed to give a 6.42 log.sub.10 reduction, whilst the diluted Proxitane sample gave only a 2.04 log.sub.10 reduction. The chlorine-based disinfectants, SDIC and Chlorclean reduced biofilm viability by 2.85 log.sub.10 and 2.82 log.sub.10 respectively. Oxivir was found to give approximately a 1 log.sub.10 reduction whereas the unformulated hydrogen peroxide gave essentially a zero log.sub.10 reduction under both clean and dirty conditions.
(181) Under dirty conditions (ie in the presence of an organic soil), Example 9 again gave a 6.42 log.sub.10 reduction. Both SDIC and Chlorclean disinfectant efficacy was significantly decreased in the presence of soil, giving log.sub.10 reductions of 0.03 and 0.02 respectively. Oxivir Tb also gave a reduced efficacy, giving a 0.24 log.sub.10 reduction of biofilm viability (See
(182) Conclusions
(183) The disinfectant solution according to Example 9, along with two other formulated, commercially available disinfectant systems, each of which contained an oxidising biocide, along with other ingredients such as surfactants. The effect of addition of the proprietary ingredients to disinfectant efficacy was evaluated by comparing the formulated disinfectants with generic equivalents in a bid to determine if biofilm removal is due to the active ingredient alone or if proprietary ingredients act in synergism with the active ingredient.
(184) The outstanding performer in this study was Example 9 which completely inactivated the Dry Surface Biofilm in the presence or absence of soil.
(185) The formulated chlorine-based product Chlorclean, as well as unformulated SIDC tablets were the next best performers, although they killed significantly less biofilm bacteria (3 Log.sub.10) than Example 9, and only in the absence of soil.
(186) Previous studies have demonstrated that, chemicals such as hypochlorite are consumed by the surface layers of the biofilm causing depletion of the neutralizing capacity before the disinfectant can penetrate into deeper layers (see reference 13) making traditional hydrated biofilm more tolerant than planktonic cells to these disinfectants. However, a study on the efficacy of hypochlorite against Dry Surface Biofilm found that this semi-dehydrated biofilm was more tolerant to hypochlorite than traditional hydrated biofilm (see reference 6).
(187) Even in the absence of soil, the hydrogen peroxide-based disinfectants killed significantly less biofilm bacteria than disinfectants based on chlorine or a combination of peracetic acid and hydrogen peroxide. Oxivir Tb killed approximated 1 Log.sub.10 of the biofilm bacteria while hydrogen peroxide solution had no effect. It is noted however that Oxivir's manufacturer's recommended contact time for killing bacteria is 10 not five minutes as used in the study and this could explain its lower performance. However, even a contact time of 5 minutes is probably excessive given the way that dry hospital surfaces are cleaned. The majority of disinfectants have no residual effect and remain active only when wet.
(188) The differences in kill rate between Example 9 (formulated additives) and diluted Proxitane (no additives) suggests that the activity of Example 9 against DSB may be governed not only by the active ingredients (hydrogen peroxide and peracetic acid), but also by other factors such as the added surfactants or excipients, chelating agents or its solution pH.
(189) Surfactants may increase diffusion of the active ingredients into the biofilm (due to a lowering of the solution surface tension, and hence improved wetting of the biofilm surface).
(190) Increased diffusion is likely to result in increased biofilm kill as all these tested disinfectants, in the absence of organic soil, can kill 7 Log.sub.10 of planktonic organisms. Chelating agents complex any calcium and magnesium ions present in the hard water, plus any other interfering metals often present in tap water such as iron, manganese and thus increase disinfectant performance in hard water.
REFERENCES
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