Isothiazolinone biocides enhanced by zinc ions

Information

  • Patent Grant
  • 9723842
  • Patent Number
    9,723,842
  • Date Filed
    Thursday, May 24, 2007
    17 years ago
  • Date Issued
    Tuesday, August 8, 2017
    7 years ago
Abstract
The present invention relates to an antimicrobial composition comprising an isothiazolinone, such as 1,2-benzisothiazolin-3-one, and a zinc compound selected from zinc salts, zinc oxides, zinc hydroxides or combinations thereof. Useful zinc salts include for example, oxides, sulfates, chlorides, and combinations thereof. In use, the zinc from the zinc compound enhances the antimicrobial activity to the isothiazolin-containing composition. This enhancement permits achieving the desired antimicrobial activity at a lower usage rate than is achieved using the isothiazolinone in the absence of the zinc compound. The antimicrobial composition can also contain co-biocides, such as pyrithiones, including zinc pyrithione or copper pyrithione.
Description
BACKGROUND OF THE INVENTION

Isothiazolinones, such as 1,2-benzisothiazolin-3-one ( also referred to as “BIT”), are know to be effective antimicrobials. BIT, as disclosed for example in formulations described in European patent EP 0 703 726, is widely used as a bactericide in a variety of applications. Illustratively, British patent publication GB2,230,190A discloses a preservative composition containing BIT and an adduct of zinc chloride (“ZC”), together with 2,2′-dithiopyridine-1,1′-dioxide (“DTP”). Example 3 of '190A publication compares compositions containing BIT plus ZC plus DTP against a control example containing only BIT plus ZC. The results given in Example 3 and Table 3 of the publication indicate that inclusion of DTP allows decreased usage of BIT in the composition. Nonetheless, the amount of BIT (2.5 ppm) employed in the control example has been found by the present inventors to be insufficient for antimicrobial efficacy in real-world applications.


While BIT has proven useful in a wide range of applications, the useful amount of BIT that can be added to a commercial product is limited by efficacy and economic considerations and to a lesser extent by environmental and toxicological concerns. Accordingly, alternative antimicrobial compositions are needed for wet state applications that are cost-effective and minimize the likelihood of adverse environmental and toxicological effects. The present invention provides one such alternative.


SUMMARY OF THE INVENTION

In one aspect, the present invention relates to an antimicrobial composition comprising (a) at least one isothiazolin-3-one and (b) at least one zinc compound selected from the group consisting of zinc salts, zinc oxides, zinc hydroxides, and combinations thereof. Illustrative zinc salts are zinc chloride, zinc sulfide, zinc carbonate, basic zinc carbonate, and combinations thereof. The zinc compound provides a source of metal ion in the antimicrobial composition. In the composition, the isothiazolin-3-one is present in an amount of from 1 to 500 ppm (preferably from 5 to 500 ppm), the zinc compound is present in an amount from 5 to 200,000 ppm (preferably from 5 to 500 ppm), and the weight ratio of the isothiazolin-3-one to the zinc compound is from 1:2000 to 100:1 (preferably from 1:100 to 100:1). Optionally, the antimicrobial composition additionally comprises a pyrithione salt or pyrithione acid. Useful pyrithione salts include copper pyrithione, zinc pyrithione, sodium pyrithione, pyrithione disulfide, and combinations thereof.


In another aspect, the present invention relates to an antimicrobial composition concentrate that, upon dilution with water, provides antimicrobial efficacy in a functional fluid. The concentrate comprises (a) at least one isothiazolin-3-one and (b) at least one zinc compound selected from the group consisting of zinc salts, zinc oxides, zinc hydroxides, and combinations thereof. In the concentrate, component (a) is present in an amount of from 1 to 95% w/w, and component (b) is present in an amount of from 1 to 50% w/w based on the total weight of the concentrate, with the proviso that the weight percent of (a) plus (b) does not exceed 100% by weight.


In yet another aspect, the present invention relates to functional fluid that comprises a base medium plus (a) at least one isothiazolin-3-one and (b) at least one zinc compound selected from the group consisting of zinc salts, zinc oxides, zinc hydroxides, and combinations thereof. Illustrative zinc salts are zinc chloride, zinc sulfide, zinc carbonate, basic zinc carbonate, and combinations thereof. In the composition, the isothiazolin-3-one is present in an amount of from 1 to 500 ppm (preferably from 5 to 500 ppm), the metal compound is present in an amount of from 5 to 200,00 ppm (preferably from 5 to 500 ppm), and the weight ratio of the isothiazolin-3-one to zinc ion is from 1:2000 to 100:1 (preferably from 100:1 to 1:100). Optionally, the antimicrobial composition additionally comprises a pyrithione salt or pyrithione acid. Useful pyrithione salts include copper pyrithione, zinc pyrithione, sodium pyrithione, and pyrithione disulfide. The base medium for the functional fluid can be, for example, a polymer useful in polymer emulsions. Examples of polymer systems are lattices, such as acrylic and substituted (meth)acrylates, styrene/butadiene, ethylene vinyl acetate, polyvinyl acetate, styrene/butadiene/N-methylol acrylamide, nitrile and copolymers of the aforementioned. Typical functional fluids include coating compositions, such as paints, adhesives, sealants, caulks, mineral and pigment slurries, printing inks, agricultural pesticide formulations, household products, personal care, metal working fluids and other aqueous based systems.


These and other aspects will become apparent upon reading the following detailed description of the invention.





BRIEF DESCRIPTION OF THE DRAWINGS


FIG. 1 provides a graphical depiction of an Isobologram showing Antimicrobial Activity of Mixtures of 1,2-Benzisothiazolin-3-one (“BIT”) and Zinc Chloride against Ps. aeruginosa based on Fractional Inhibitory Concentration values.



FIG. 2 provides a graphical depiction of an Isobologram showing Antimicrobial Activity of Mixtures of Kathon® (a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one (“CIMIT”) and 2-methyl-4-isothiazolin-3-one (“MIT”)) and Zinc Chloride against Ps. aeruginosa based on Fractional Inhibitory Concentration values.



FIG. 3 provides a graphical depiction of an Isobologram showing Antimicrobial Activity of Mixtures of MIT and Zinc Chloride against Ps. aeruginosa based on Fractional Inhibitory Concentration values.



FIG. 4 provides a graphical depiction of an Isobologram showing Antimicrobial Activity of Mixtures of N-(n-butyl)-1,2-benzisothiazolin-3-one (“BBIT”) and Zinc Chloride against Ps. aeruginosa based on Fractional Inhibitory Concentration values.



FIG. 5 provides a graphical depiction of an Isobologram showing Antimicrobial Activity of Mixtures of BIT and Sodium Chloride against Ps. aeruginosa based on Fractional Inhibitory Concentration values.





DETAILED DESCRIPTION OF THE INVENTION

It has now been surprisingly found in accordance with the present invention that an antimicrobial composition containing an isothiazolin-3-one, plus a zinc compound selected from the group consisting of zinc salts, zinc oxides, zinc hydroxides, and combinations thereof, exhibits enhanced antimicrobial efficacy, as compared to isothiazolin-containing compositions that do not contain the metal compound. Enhanced efficacy are suitably provided in antimicrobial compositions over a wide range of pHs of from 3 to 12.


The antimicrobial composition of the present invention is suitably incorporated into a functional fluid. The functional fluid suitably comprises a base medium plus (a) at least one isothiazolin-3-one and (b) at least one zinc compound selected from the group consisting of zinc salts of organic acids, zinc salts of inorganic acids, zinc oxides, zinc hydroxides, and combinations thereof. Illustrative zinc salts include zinc chloride, zinc sulfide, zinc carbonate, basic zinc carbonate (also known as “hydroxy-containing zinc carbonate”, also know as “zinc hydroxy carbonate” which is further identified by the empirical formula Zn5(OH)6(CO3)2), and combinations thereof.


The isothiazolinone useful in the present invention is preferably an isothiazolin-3-one that is selected from: 1,2-benzisothiazolin-3-one (“BIT”), N-(n-butyl)-1,2-benzisothiazolin-3-one (“BBIT”), 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (“DCOIT”), 2-methyl-4-isothiazolin-3-one (“MIT”), mixtures of 5-chloro-2-methyl-4-isothiazolin-3-one (“CIMIT”) plus MIT (available from Rohm and Haas Company, Philadelphia, Pa. under the tradename Kathon®) dithio-2,2′-bis(benzmethylamide), and combinations thereof. Particularly preferred isothiazolins are BIT, MIT and BBIT, and combinations thereof.


In the composition, the isothiazolin-3-one is present in an amount of from 1 to 500 ppm (preferably from 5 to 500 ppm), the zinc compound is present in an amount of from 5 to 200,000 ppm (preferably from 5 to 500 ppm), and the weight ratio of the isothiazolin-3-one to the zinc compound is from 1:2000 to 100:1 (preferably from 100:1 to 1:100).


Optionally, the antimicrobial composition additionally comprises a pyrithione salt or pyrithione acid. Useful pyrithione salts include copper pyrithione, zinc pyrithione, sodium pyrithione. If used, the pyrithione salt or pyrithione acid is suitably present in the composition in an amount of from about 0.001% w/w to about 1.0% w/w.


In one embodiment, the combination of antimicrobial components for the antimicrobial composition can be provided in the form of an antimicrobial composition concentrate that, upon dilution with water, provides antimicrobial efficacy in a functional fluid. The concentrate comprises (a) at least one isothiazolin-3-one and (b) at least one zinc compound selected from the group consisting of zinc salts, zinc oxides, zinc hydroxides, and combinations thereof. In the concentrate, component (a) is present in an amount of from 1 to 95% w/w, and component (b) is present in an amount of from 1 to 50% w/w.


The antimicrobial compositions of the present invention are suitably used in functional fluids such as polymer emulsions, or other coating compositions, to impart both wet state and dry film preservation. The base medium can be, for example, a polymer useful in polymer emulsions wherein the polymer is selected from the group consisting of acrylic and substituted (meth)acrylates, styrene/butadiene, ethylene vinyl acetate, polyvinyl acetate, styrene/butadiene/N-methylol acrylamide, nitrile and copolymers of the aforementioned. Typical functional fluids include coating compositions, such as paints, adhesives, sealants, caulks, mineral and pigment slurries, printing inks, agricultural pesticide formulations, household products, personal care, metal working fluids and other aqueous based systems.


The invention is further described in the Examples given below. All percentages given herein are weight percents based on the total weight of the composition, unless otherwise stated. All patents referred to in this application are incorporated herein by reference in their entirety.


EXAMPLE 1

In this example, samples of a commercial water based acrylic latex, trade name REVACRYL 1A, supplied by the Harlow Chemical Company, pH 8.1, containing antimicrobial additives in amounts as identified in Table I below, were challenged with a bacterial suspension consisting of

  • Pseudomonas aeruginosa, NCIMB 8295
  • Providencia rettgeri, NCIMB 10842
  • Serratia marcescens, NCIMB 9523
  • Aeromonas hydrophila, NCIMB9233
  • Alcaligenes spp. (Wet State Preservation isolate)
  • Burkholderia cepacia, ATCC 25416
  • Pseudomonas putida, NCIMB9494


All test species were cultured onto nutrient agar and incubated for 24 hours at 30° C. After this period individual suspensions of each test organism were prepared at a concentration of 106 colony forming units per ml in saline solution by means of a Thoma counting chamber, achieved by mixing equal volumes of the individual suspensions. The concentration of bacteria in each aliquot after each challenge was 2×106 per ml.


The antimicrobial additive-containing paint samples were stored at 40° C. for 7 days prior to commencing the test. The paint samples were challenged with 1% v/v of bacterial suspension as described above. All test samples were incubated at 30° C. for the duration of the test and examined for viable bacteria after 1, 3 and 7 days after each challenge. Viable bacteria were detected by streaking aliquots onto nutrient agar followed by incubation at 30° C. for 2 days.


Table I presents the results obtained after the third inoculation days 1, 3 and 7.










TABLE I








3rd inoculation











Sample
BIT/ppm
Day 1
Day 3
Day 7














BIT/ZnO
50
C
C
C



100
1+ (92)
1+ (27)




150
1+ (95)
S (7)




200
S (10)
T (4)




250
1+ (89)
1+ (22)




300
1+ (77)
1+ (12)



BIT/ZnCl2
50
C
C
C



100
++
1+ (30)




150
1+ (34)
1+ (21)




200
1+ (51)
1+ (14)




250
 ++ (185)
1+ (25)




300
1+ (58)
1+ (17)



PROXEL BD20
50
C
C
C



100
C
C
C



150
C
C
C



200
C
C
C



250
1+ (75)





300
1+ (54)





400
1+ (47)







Assessments are rated as:


— no growth detected


T 0-5 colonies present


S 5-10 colonies


1+ 20-100 colonies


+ light growth - no specified number of colonies


++ moderate growth - colonies visible, some coalescence


+++ heavy growth - coalescing colonies visible throughout


C confluent heavy growth






Results demonstrate a potentiating effect on BIT in combination with a zinc containing salt when compared against a commercial product, namely PROXEL BD20 a product of Arch Chemicals, Inc. containing only a BIT for the preservation of a commercial latex in that only 100 ppm of BIT is required in the presence of a zince containing salt compared to 250 ppm of BIT for sample containing only BIT.


EXAMPLE 2

Investigation of Potentiation Between 1,2-Benzisothiazolin-3-one (BIT) and Zinc Chloride (ZnCl2) Against Pseudomonas aeruginosa.


Bacteria



Pseudomonas aeruginosa (NCIB 10421) maintained on nutrient agar, were used to study the synergy between BIT and ZnCl2.


Calculation of Minimum Inhibitory Concentrations Against Mono-cultures


Bacteria were grown to stationary phase (approximately 24 hours) in nutrient broth (approximately 109 organisms per ml). A 0.1% (v/v) inoculum was used to seed fresh medium and 100 μl of the inoculum was then added to each well of a microtitre plate, except for the first well which contained 200 μl.


Using doubling dilutions, the concentration of the compounds under investigation were varied in each well along the ordinate axis. The presence or absence of growth was recorded by visual inspection after 24 hours incubation at 37° C.


Calculation of Antimicrobial Activity Against Mono-cultures


Microtitre plates were used for this assay. A simple matrix was constructed with varied concentrations of the two compounds from 2×MIC (minimum inhibitory concentration) down to zero concentration in a 10×10 array. As the microtitre plate has only 96 wells, the combinations of the two compounds that made up the extreme concentrations (highest and lowest) were omitted. Solutions were made up in broth at two times the final concentrations after pre-dissolving the compounds in distilled water.


The mixture (100 μl) was added to the plate so that the total volume in each well was 200 μl. Nutrient broth was used for Ps. aeruginosa. Plates were incubated for 16-24 hours at 37°. The presence or absence of growth was determined by visual inspection.


Results for Example 2


Table 2: Antimicrobial Activity of Compounds Under Investigation











TABLE 2








MIC (ppm) against





Ps. aeruginosa















COMPOUND
1
2
3
4
















BIT
30
42
42
30



ZnCl2
300
450
375
450





BIT is 1,2-benzisothiazolin-3-one available from Arch Limited PROXEL ® GXL.







Calculation of activity Against Mono-cultures


The Minimum Inhibitory Concentration (MIC) is the lowest concentration of biocide which showed growth inhibition when used alone. For the purpose of Fractional Inhibitory Concentration (FIC) calculations, if a single biocide did not control growth, the MIC was taken as the highest concentration used. A Fractional Inhibitory Concentration is the concentration of biocide which controlled growth in the mixture divided by the MIC of that biocide. FIC values for both compounds in the mixture were calculated and the results are shown in Table 3. The sum of these two figures gives an indication of the action of the two biocides. A value less than one indicates an enhanced effect, if the total is unity or greater the action is additive and if the value is greater than two the biocides are antagonistic.


Table 3: Fractional Inhibitory Concentrations for 1,2-Benzisothiazolin-3-one (BIT) and Zinc Chloride (ZnCl2) against Ps. aeruginosa










TABLE 3








FIC VALUES












COMPOUND
1
2
3
4
























BIT
1
0.20
0.20
0.40
0.14
0.14
0.29
0.29
0.43
0.14
0.20
0.40
0


ZnCl2
0
0.25
0.50
0.25
0.33
0.50
0.17
0.33
0.17
0.60
0.33
0.17
1


Total
1
0.45
0.70
0.65
0.47
0.64
0.46
0.62
0.60
0.74
0.53
0.57
1









If a graph with the axes representing the biocide Fractional Inhibitory Concentrations for the two biocides on linear scales is constructed, when the combination is additive the isobole ( i.e. the line joining the points that represent all combinations with the same effect including the equally effective concentrations of the biocides used alone) is straight, enhanced combinations give concave isoboles and antagonistic combinations give convex isoboles. As shown in FIG. 1, the combination of BIT and ZnCl2 has an enhanced effect against Ps. aeruginosa as confirmed by the concave isobole on the graph of FIG. 1.


EXAMPLE 3

Investigation of potentiation between Kathon® (CIMIT/MIT) and Zinc Chloride (ZnCl2) against Pseudomonas aeruginosa.


Bacteria



Pseudomonas aeruginosa (NCIB 10421) maintained on nutrient agar, were used to study the synergy of Kathon® and ZnCl2.


Calculation of Minimum Inhibitory Concentrations Against Mono-cultures


Bacteria were grown to stationary phase (approximately 24 hours) in nutrient broth (approximately 109 organisms per ml). A 0.1% (v/v) inoculum was used to seed fresh medium and 100 μl of the inoculum was then added to each well of a microtitre plate, except for the first well which contained 200 μl.


Using doubling dilutions, the concentration of the compounds under investigation were varied in each well along the ordinate axis. The presence or absence of growth was recorded by visual inspection after 24 hours incubation at 37° C.


Calculation of Antimicrobial Activity Against Mono-cultures


Microtitre plates were used for this assay. A simple matrix was constructed with varied concentrations of the two compounds from 2×MIC (minimum inhibitory concentration) down to zero concentration in a 10×10 array. As the microtitre plate has only 96 wells, the combinations of the two compounds that made up the extreme concentrations (highest and lowest) were omitted. Solutions were made up in broth at two times the final concentrations after pre-dissolving the compounds in distilled water.


The mixture (100 μl) was added to the plate so that the total volume in each well was 200 μl. Nutrient broth was used for Ps. aeruginosa. Plates were incubated for 16-24 hours at 37°. The presence or absence of growth was determined by visual inspection.


Results of Example 3


Table 4: Antimicrobial Activity of Compounds Under Investigation











TABLE 4








MIC (ppm)




against Ps. aeruginosa














COMPOUND
1
2
3
4
















Kathon
0.9
0.9
0.9
0.53



ZnCl2
294
294
210
600









The mixture of CIMIT and MIT is available from Rohm and Haas Company, Philadelphia, Pa. under the tradename Kathon®.


Calculation of Synergy Against Mono-cultures


The Minimum Inhibitory Concentration (MIC) is the lowest concentration of biocide which showed growth inhibition when used alone. For the purpose of Fractional Inhibitory Concentration (FIC) calculations, if a single biocide did not control growth, the MIC was taken as the highest concentration used. A Fractional Inhibitory Concentration is the concentration of biocide which controlled growth in the mixture divided by the MIC of that biocide. FIC values for both compounds in the mixture were calculated and the results are shown in Table 5. The sum of these two figures gives an indication of the action of the two biocides. A value less than one indicates an enhanced effect, if the total is unity or greater the action is additive and if the value is greater than two the biocides are antagonistic.


Table 5: Fractional Inhibitory Concentrations for Kathon (CIMIT/MIT) and Zinc Chloride (ZnCl2) against Ps. aeruginosa










TABLE 5








FIC VALUES












COMPOUND
1
2
3
4























Kathon
1
0.17
0.17
0.33
0.33
0.17
0.33
0.33
0.14
0.28
0.28
0


ZnCl2
0
0.14
0.29
0.14
0.29
0.29
0.14
0.29
0.50
0.38
0.50
1


Total
1
0.31
0.46
0.47
0.62
0.46
0.47
0.62
0.64
0.66
0.78
1









If a graph with the axes representing the biocide Fractional Inhibitory Concentrations for the two biocides on linear scales is constructed, when the combination is additive the isobole (i.e. the line joining the points that represent all combinations with the same effect including the equally effective concentrations of the biocides used alone) is straight, enhanced combinations give concave isoboles and antagonistic combinations give convex isoboles. As shown in FIG. 2, the combination of Kathon® and ZnCl2 has an enhanced effect against Ps. aeruginosa as confirmed by the concave isobole in FIG. 2.


EXAMPLE 4

Investigation of potentiation between MIT and Zinc Chloride (ZnCl2) against Pseudomonas aeruginosa


Bacteria



Pseudomonas aeruginosa (NCIB 10421) maintained on nutrient agar, were used to study the synergy between MIT and ZnCl2.


Calculation of Minimum Inhibitory Concentrations Against Mono-cultures


Bacteria were grown to stationary phase (approximately 24 hours) in nutrient broth (approximately 109 organisms per ml). A 0.1% (v/v) inoculum was used to seed fresh medium and 100 μl of the inoculum was then added to each well of a microtitre plate, except for the first well which contained 200 μl.


Using doubling dilutions, the concentration of the compounds under investigation were varied in each well along the ordinate axis. The presence or absence of growth was recorded by visual inspection after 24 hours incubation at 37° C.


Calculation of Antimicrobial Activity Against Mono-cultures


Microtitre plates were used for this assay. A simple matrix was constructed with varied concentrations of the two compounds from 2×MIC (minimum inhibitory concentration) down to zero concentration in a 10×10 array. As the microtitre plate has only 96 wells, the combinations of the two compounds that made up the extreme concentrations (highest and lowest) were omitted. Solutions were made up in broth at two times the final concentrations after pre-dissolving the compounds in distilled water.


The mixture (100 μl) was added to the plate so that the total volume in each well was 200 μl. Nutrient broth was used for Ps. aeruginosa. Plates were incubated for 16-24 hours at 37°. The presence or absence of growth was determined by visual inspection.


Results of Example 4


Table 6: Antimicrobial Activity of Compounds Under Investigation











TABLE 6








MIC (ppm)




against Ps. aeruginosa














COMPOUND
1
2
3
4
















MIT
9
6
10.5
8



ZnCl2
210
210
450
450










Calculation of Synergy Against Mono-cultures


The Minimum Inhibitory Concentration (MIC) is the lowest concentration of biocide which showed growth inhibition when used alone. For the purpose of Fractional Inhibitory Concentration (FIC) calculations, if a single biocide did not control growth, the MIC was taken as the highest concentration used. A Fractional Inhibitory Concentration is the concentration of biocide which controlled growth in the mixture divided by the MIC of that biocide. FIC values for both compounds in the mixture were calculated and the results are shown in Table 7. The sum of these two figures gives an indication of the action of the two biocides. A value less than one indicates an enhanced effect, if the total is unity or greater the action is additive and if the value is greater than two the biocides are antagonistic.


Table 7: Fractional Inhibitory Concentrations for (MIT) and Zinc Chloride (ZnCl2) against Ps. aeruginosa










TABLE 7








FIC Values












COMPOUND
1
2
3
4























MIT
1
0.17
0.33
0.33
0.50
0.25
0.50
0.75
0.14
0.29
0.17
0


ZnCl2
0
0.57
0.29
0.43
0.14
0.43
0.29
0.14
0.33
0.17
0.50
1


Total
1
0.74
0.62
0.76
0.64
0.68
0.79
0.89
0.48
0.46
0.67
1









If a graph with the axes representing the biocide Fractional Inhibitory Concentrations for the two biocides on linear scales is constructed, when the combination is additive the isobole (i.e. the line joining the points that represent all combinations with the same effect including the equally effective concentrations of the biocides used alone) is straight, enhanced combinations give concave isoboles and antagonistic combinations give convex isoboles. As shown in FIG. 3, the combination of MIT and ZnCl2 has an enhanced effect against Ps. aeruginosaas confirmed by the concave isobole in FIG. 3.


EXAMPLE 5

Investigation of Potentiation between BBIT and Zinc Chloride (ZnCl2) against Pseudomonas aeruginosa.


Bacteria



Pseudomonas aeruginosa (NCIB 10421) maintained on nutrient agar, were used to study the synergy between BBIT and ZnCl2.


Calculation of Minimum Inhibitory Concentrations Against Mono-cultures


Bacteria were grown to stationary phase (approximately 24 hours) in nutrient broth (approximately 109 organisms per ml). A 0.1% (v/v) inoculum was used to seed fresh medium and 100 μl of the inoculum was then added to each well of a microtitre plate, except for the first well which contained 200 μl.


Using doubling dilutions, the concentration of the compounds under investigation were varied in each well along the ordinate axis. The presence or absence of growth was recorded by visual inspection after 24 hours incubation at 37° C.


Calculation of Antimicrobial Activity Against Mono-cultures


Microtitre plates were used for this assay. A simple matrix was constructed with varied concentrations of the two compounds from 2×MIC (minimum inhibitory concentration) down to zero concentration in a 10×10 array. As the microtitre plate has only 96 wells, the combinations of the two compounds that made up the extreme concentrations (highest and lowest) were omitted. Solutions were made up in broth at two times the final concentrations after pre-dissolving the compounds in distilled water.


The mixture (100 μl) was added to the plate so that the total volume in each well was 200 μl. Nutrient broth was used for Ps. aeruginosa. Plates were incubated for 16-24 hours at 37°. The presence or absence of growth was determined by visual inspection.


Results of Example 5


Table 8: Antimicrobial Activity of Compounds Under Investigation











TABLE 8








MIC (ppm)




against Ps. aeruginosa














COMPOUND
1
2
3
4
















BBIT
315
360
42
180



ZnCl2
525
525
600
600





BBIT is N-(butyl)-1,2-benzisothiazolin-3-one.







Calculation of Synergy Against Mono-cultures


The Minimum Inhibitory Concentration (MIC) is the lowest concentration of biocide which showed growth inhibition when used alone. For the purpose of Fractional Inhibitory Concentration (FIC) calculations, if a single biocide did not control growth, the MIC was taken as the highest concentration used. A Fractional Inhibitory Concentration is the concentration of biocide which controlled growth in the mixture divided by the MIC of that biocide. FIC values for both compounds in the mixture were calculated and the results are shown in Table 9. The sum of these two figures gives an indication of the action of the two biocides. A value less than one indicates an enhanced effect, if the total is unity or greater the action is additive and if the value is greater than two the biocides are antagonistic.


Table 9: Fractional Inhibitory Concentrations for BBIT and Zinc Chloride (ZnCl2) against Ps. aeruginosa










TABLE 9








FIC values












COMPOUND
1
2
3
4


















BBIT
1
0.29
0.25
0.14
0.71
0.25
0


ZnCl2
0
0.43
0.43
0.50
0.38
0.38
1


Total
1
0.71
0.68
0.64
1.09
0.63
1









If a graph with the axes representing the biocide Fractional Inhibitory Concentrations for the two biocides on linear scales is constructed, when the combination is additive the isobole (i.e. the line joining the points that represent all combinations with the same effect including the equally effective concentrations of the biocides used alone) is straight, enhanced combinations give concave isoboles and antagonistic combinations give convex isoboles. As shown in FIG. 4, the combination of BBIT and ZnCl2 has an enhanced effect against Ps. aeruginosa as confirmed by the concave isobole shown in FIG. 4.


COMPARATIVE EXAMPLE A

Investigation of potentiation between 1,2-Benzisothiazolin-3-one (BIT) and Sodium Chloride (NaCl2) against Pseudomonas aeruginosa as compared to the Synergy between 1,2-Benzisothiazolin-3-one (BIT) and Zinc Chloride (ZnCl2) against Pseudomonas aeruginosa (Example 2)


Bacteria



Pseudomonas aeruginosa (NCIB 10421) maintained on nutrient agar, were used to study the efficacy of the combination of BIT with sodium chloride.


Calculation of Minimum Inhibitory Concentrations Against Mono-cultures


Bacteria were grown to stationary phase (approximately 24 hours) in nutrient broth (approximately 109 organisms per ml). A 0.1% (v/v) inoculum was used to seed fresh medium and 100 μl of the inoculum was then added to each well of a microtitre plate, except for the first well which contained 200 μl.


Using doubling dilutions, the concentration of the compounds under investigation were varied in each well along the ordinate axis. The presence or absence of growth was recorded by visual inspection after 24 hours incubation at 37° C.


Calculation of Antimicrobial Activity Against Mono-cultures


Microtitre plates were used for this assay. A simple matrix was constructed with varied concentrations of the two compounds from 2×MIC (minimum inhibitory concentration) down to zero concentration in a 10×10 array. As the microtitre plate has only 96 wells, the combinations of the two compounds that made up the extreme concentrations (highest and lowest) were omitted. Solutions were made up in broth at two times the final concentrations after pre-dissolving the compounds in distilled water.


The mixture (100 μl) was added to the plate so that the total volume in each well was 200 μl. Nutrient broth was used for Ps. aeruginosa. Plates were incubated for 16-24 hours at 37° . The presence or absence of growth was determined by visual inspection.


Results of Comparative Example A


Table 10: Antimicrobial Activity of Compounds Under Investigation











TABLE 10






COMPOUND
MIC (ppm) against Ps. aeruginosa








BIT
30



NaCl2
None detected (greater than 675)





BIT is 1,2-benzisothizolin-3-one available from Arch Limited as PROXELRTM GXL.







Calculation of Potentiation Against Mono-Cultures


The Minimum Inhibitory Concentration (MIC) is the lowest concentration of biocide which showed growth inhibition when used alone. For the purpose of Fractional Inhibitory Concentration (FIC) calculations, if a single biocide did not control growth, the MIC was taken as the highest concentration used. A Fractional Inhibitory Concentration is the concentration of biocide which controlled growth in the mixture divided by the MIC of that biocide. FIC values for both compounds in the mixture were calculated and the results are shown in Table 11. The sum of these two figures gives an indication of the action of the two biocides. A value less than one indicates an enhanced effect, if the total is unity or greater the action is additive and if the value is greater than two the biocides are antagonistic.


Table 11: Fractional Inhibitory Concentrations for 1,2-Benzisothiazolin-3-one (BIT) and Sodium Chloride (NaCl2) against Ps. aeruginosa











TABLE 11






COMPOUND
FIC VALUES




















BIT
1
1.00
0



NaCl2
0
0.33
1



Total
1
1.33
1









If a graph with the axes representing the biocide Fractional Inhibitory Concentrations for the two biocides on linear scales is constructed, when the combination is additive the isobole ( i.e. the line joining the points that represent all combinations with the same effect including the equally effective concentrations of the biocides used alone) is straight, enhanced combinations give concave isoboles and antagonistic combinations give convex isoboles. As shown in FIG. 5, the combination of BIT and NaCl2 is additive against Ps. aeruginosa as confirmed by the straight isobole in FIG. 5. Additionally, the results of this Example further illustrate that the combination of an isothiazolin-3-one such as BIT and a zinc compound such as ZnCl2, as shown in Example 2, show unexpected potentiation results against Ps. aeruginosa.

Claims
  • 1. An antimicrobial composition comprising: (a) at least one isothiazolin-3-one selected from the group consisting of 1,2-benzisothiazolin-3-one, N-(n-butyl)-1,2-benzisothiazolin-3-one, and combinations thereof; and(b) at least one zinc compound comprising zinc chloride, zinc oxide, or a combination thereof;wherein the isothiazolin-3-one is present in an amount of from 1 to 500 ppm,wherein the zinc compound is present in an amount of from 5 to 200,000 ppm, andwherein the weight ratio of the isothiazolin-3-one to the zinc compound is from 1:100 to 100:1.
  • 2. The composition of claim 1 wherein component (a) is present in an amount of from 5 to 500 ppm, and component (b) is present in an amount of from 5 to 500 ppm.
  • 3. A functional fluid composition comprising: a polymer emulsion; anda wet state preservative comprising an antimicrobial composition comprising at least one isothiazolin-3-one selected from the group consisting of 1,2-benzisothiazolin-3-one, N-(n-butyl)-1,2-benzisothiazolin-3-one, and combinations thereof, andat least one zinc compound comprising zinc chloride, zinc oxide, or a combination thereof,wherein the isothiazolin-3-one is present in an amount of from 1 to 500 ppm,wherein the zinc compound is present in an amount of from 5 to 200,000 ppm, andwherein the weight ratio of the isothiazolin-3-one to the zinc compound is from 1:100 to 100:1.
  • 4. The composition of claim 3 which further comprises a co-biocide selected from the group consisting of pyrithione salts, pyrithione acids, and combinations thereof, and wherein said co-biocide is present in said composition in an amount of from about 0.001 to about 1.0% w/w based on the total weight of said composition.
  • 5. The composition of claim 4 wherein said pyrithione salts are selected from the group consisting of copper pyrithione, zinc pyrithione, sodium pyrithione, and combinations thereof.
  • 6. A coating composition comprising: a base medium selected from the group consisting of paints, adhesives, sealants, caulks, mineral and pigment slurries, printing inks, agricultural pesticide formulations, household coating products, personal care products, metal working fluids, and combinations thereof; anda wet state preservative comprising an antimicrobial composition comprising at least one isothiazolin-3-one selected from the group consisting of 1,2-benzisothiazolin-3-one, N-(n-butyl)-1,2-benzisothiazolin-3-one, and combinations thereof, andat least one zinc compound comprising zinc chloride, zinc oxide, or a combination thereof,wherein the isothiazolin-3-one is present in an amount of from 1 to 500 ppm,wherein the zinc compound is present in an amount of from 5 to 200,000 ppm, andwherein the weight ratio of the isothiazolin-3-one to the zinc compound is from 1:100 to 100:1.
  • 7. An antimicrobial composition comprising: (a) 1,2-benzisothiazolin-3-one;(b) zinc oxide; andwherein the isothiazolin-3-one is present in an amount from 1 to 500 ppm,wherein the zinc oxide is present in an amount from 5 to 200,000 ppm, andwherein the weight ratio of the isothiazolin-3-one to the zinc oxide is from 1:100 to 100:1.
  • 8. The antimicrobial composition of claim 7 wherein component (a) is present in an amount of from 5 to 500 ppm, and component (b) is present in an amount of from 5 to 500 ppm.
  • 9. The antimicrobial composition of claim 7 which further comprises a co-biocide selected from the group consisting of pyrithione salts, pyrithione acids, and combinations thereof, and wherein said co-biocide is present in said composition in an amount of from about 0.001 to about 1% w/w based on the total weight of said composition.
  • 10. The antimicrobial composition of claim 1, wherein the at least one zinc compound is zinc oxide.
  • 11. The antimicrobial composition of claim 1, wherein the at least one zinc compound is zinc chloride.
  • 12. The antimicrobial composition of claim 1, wherein the composition further comprises a co-biocide selected from the group consisting of pyrithione salts, pyrithione acids, and combinations thereof.
  • 13. The functional fluid composition of claim 3, wherein the at least one zinc compound is zinc oxide.
  • 14. The functional fluid composition of claim 3, wherein the at least one zinc compound is zinc chloride.
  • 15. The coating composition of claim 6, wherein the at least one zinc compound is zinc oxide.
  • 16. The coating composition of claim 6, wherein the at least one zinc compound is zinc chloride.
  • 17. The antimicrobial composition of claim 1, the composition consisting of the at least one isothiazolin-3-one, the at least one zinc compound, optionally at least one polymer base medium, and optionally a co-biocide.
  • 18. The antimicrobial composition of claim 7 wherein the composition further comprises zinc pyrithione.
  • 19. The antimicrobial composition of claim 1, wherein the composition comprises 1,2-benzisothiazolin-3-one and zinc chloride.
  • 20. The antimicrobial composition of claim 10, wherein the composition further comprises a co-biocide selected from the group consisting of pyrithione salts, pyrithione acids, and combinations thereof.
  • 21. The antimicrobial composition of claim 20, wherein the pyrithione salt comprises zinc pyrithione.
  • 22. The antimicrobial composition of claim 11, wherein the composition further comprises a co-biocide selected from the group consisting of pyrithione salts, pyrithione acids, and combinations thereof.
  • 23. The antimicrobial composition of claim 22, wherein the pyrithione salt comprises zinc pyrithione.
  • 24. The antimicrobial composition of claim 1, wherein the composition further comprises a pyrithione salt selected from the group consisting of copper pyrithione, zinc pyrithione, sodium pyrithione, and combinations thereof.
  • 25. The antimicrobial composition of claim 24, wherein the pyrithione salt comprises zinc pyrithione.
  • 26. The composition of claim 4, wherein the pyrithione salt comprises zinc pyrithione.
  • 27. The composition of claim 13, wherein the composition further comprises a co-biocide selected from the group consisting of pyrithione salts, pyrithione acids, and combinations thereof.
  • 28. The composition of claim 27, wherein the pyrithione salt comprises zinc pyrithione.
  • 29. The composition of claim 14, wherein the composition further comprises a co-biocide selected from the group consisting of pyrithione salts, pyrithione acids, and combinations thereof.
  • 30. The composition of claim 29, wherein the pyrithione salt comprises zinc pyrithione.
  • 31. The composition of claim 3, wherein the composition further comprises a pyrithione salt selected from the group consisting of copper pyrithione, zinc pyrithione, sodium pyrithione, and combinations thereof.
  • 32. The composition of claim 15, wherein the composition further comprises a co-biocide selected from the group consisting of pyrithione salts, pyrithione acids, and combinations thereof.
  • 33. The composition of claim 32, wherein the pyrithione salt comprises zinc pyrithione.
  • 34. The composition of claim 16, wherein the composition further comprises a co-biocide selected from the group consisting of pyrithione salts, pyrithione acids, and combinations thereof.
  • 35. The composition of claim 34, wherein the pyrithione salt comprises zinc pyrithione.
  • 36. The composition of claim 6, wherein the composition further comprises a pyrithione salt selected from the group consisting of copper pyrithione, zinc pyrithione, sodium pyrithione, and combinations thereof.
  • 37. The composition of claim 36, wherein the pyrithione salt comprises zinc pyrithione.
  • 38. The composition of claim 7, wherein the composition further comprises a pyrithione salt selected from the group consisting of copper pyrithione, sodium pyrithione, and combinations thereof.
  • 39. A functional fluid composition comprising: a polymer emulsion; anda wet state preservative comprising an antimicrobial composition comprising at least one isothiazolin-3-one selected from the group consisting of 1,2-benzisothiazolin-3-one, N-(n-butyl)-1,2-benzisothiazolin-3-one, and combinations thereof, andat least one zinc compound comprising zinc chloride, zinc sulfide, zinc carbonate, zinc oxide, zinc hydroxide, or a combination thereof,wherein the wet state preservative is present in the fluid composition in a total amount from about 10 ppm to about 400 ppm, andwherein the molar ratio of the at least one isothiazolin-3-one to the at least one zinc compound is from about 4:1 and about 1:2.
CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/808,697, filed May 26, 2006, the disclosure of which is incorporated herein by reference in its entirety.

US Referenced Citations (31)
Number Name Date Kind
3403119 McCarthy et al. Sep 1968 A
3976501 Blue Aug 1976 A
4031055 Dupont et al. Jun 1977 A
4150026 Miller et al. Apr 1979 A
4241214 Miller et al. Dec 1980 A
4299749 McCarthy et al. Nov 1981 A
5059456 Larson et al. Oct 1991 A
5125967 Morpeth et al. Jun 1992 A
5208272 LeSota May 1993 A
5221530 Janchitraponvej et al. Jun 1993 A
5227156 Wiese Jul 1993 A
5290810 Austin Mar 1994 A
5696083 Nelson, Jr. Dec 1997 A
5723112 Bowser et al. Mar 1998 A
5840790 Ong Nov 1998 A
5883154 Kappock et al. Mar 1999 A
6133300 Smith et al. Oct 2000 A
6156108 Wachowiak, Jr. Dec 2000 A
6433056 Burdick et al. Aug 2002 B1
6455558 Bath et al. Sep 2002 B1
7025952 Traynor et al. Apr 2006 B1
20030071075 Frankenbach Apr 2003 A1
20040014736 El A'mma et al. Jan 2004 A1
20040014799 Antoni-Zimmermann et al. Jan 2004 A1
20040198713 Heer et al. Oct 2004 A1
20050065232 Okimoto et al. Mar 2005 A1
20050101487 Beilfuss May 2005 A1
20050197366 Chia et al. Sep 2005 A1
20060009553 Sin Jan 2006 A1
20060111410 Wachtler et al. May 2006 A1
20070275945 Lindner Nov 2007 A1
Foreign Referenced Citations (24)
Number Date Country
0249328 Dec 1987 EP
0425143 May 1991 EP
0455379 Nov 1991 EP
0492811 Jul 1992 EP
1527685 May 2005 EP
2200846 Aug 1988 GB
2230190 Oct 1990 GB
S62-070301 Mar 1987 JP
H04-273852 Sep 1992 JP
H08-231317 Sep 1996 JP
H09-301805 Nov 1997 JP
2003-055116 Feb 2003 JP
2004-051635 Feb 2004 JP
2005-281305 Oct 2005 JP
9201380 Feb 1992 WO
WO 9403146 Feb 1994 WO
9500019 May 1995 WO
9622023 Jul 1996 WO
WO 9836904 Aug 1998 WO
9965315 Dec 1999 WO
WO 0038520 Jul 2000 WO
WO 2004014416 Feb 2004 WO
WO 2004099308 Nov 2004 WO
WO 2007139645 Dec 2007 WO
Non-Patent Literature Citations (11)
Entry
Bulmer et al., “The antifungal action of dandruff shampoos”, 1999, Mycophathologia, vol. 147, pp. 63-65.
Simpson et al., Long term protection with fungicide and algicide development, PPCJ (1996).
Mattei et al., Formulating Stable Latex Paints With Zinc Oxide, Presented at the 68th Annual Meeting of the Federation of Societies for Coatings Technology in Washington, DC (1991).
Database WPI Section Ch, Week 8224, Derwent Publication Ltd., London, GB; Class C01, AN 82-94133E, XP002114948 & JP57156405A (Yoshitomi Pharm Ind KK), Sep. 27, 1982 (Sep. 27, 1982) abstract.
Third Party Observations for EP 07809194.9, Dated Feb. 27, 2015.
Proxel® BZ Preservative Technical Sheet, EPA Accepted Date of Apr. 22, 1999.
Proxel® BZ Preservative Technical Sheet, EPA Accepted Date of Feb. 27, 2002.
Examination Report of EP07809194.9, Dated Jan. 29, 2015.
Third Party Observations in EP07809194.9, Dated Dec. 3, 2014.
Third Party Observations for EP 07809194.9, Dated Jun. 8, 2016.
Third Party Observations for EP 07809194.9, Dated Jun. 23, 2016.
Related Publications (1)
Number Date Country
20070275094 A1 Nov 2007 US
Provisional Applications (1)
Number Date Country
60808697 May 2006 US