Microbicidal composition

Abstract

A synergistic microbicidal composition comprising a non-ionic surfactant and glutaraldehyde and a method for inhibiting the growth of microorganisms in an aqueous medium.

Claims

1. A synergistic microbicidal composition comprising: (a) a nonionic surfactant with structure:
R.sup.2O(CH.sub.2CH(CH.sub.3)O).sub.3(CH.sub.2CH.sub.2O).sub.7H where R.sup.2 is a mixture of C.sub.8-C.sub.14 linear alkyl groups; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 17:1 to 1:4.

2. A method for controlling the growth of microorganisms in an aqueous medium; the method comprising adding to the aqueous medium the synergistic microbicidal composition of claim 1.

3. A synergistic microbicidal composition comprising: (a) a nonionic surfactant with structure:
R.sup.2O(CH.sub.2CH(CH.sub.3)O).sub.3(CH.sub.2CH.sub.2O).sub.5H where R.sup.2 is a mixture of C.sub.8-C.sub.14 linear alkyl groups; and (b) glutaraldehyde; wherein a weight ratio of glutaraldehyde to nonionic surfactant is from 17:1 to 3:1.

4. A method for controlling the growth of microorganisms in an aqueous medium; the method comprising adding to the aqueous medium the synergistic microbicidal composition of claim 3.

5. A synergistic microbicidal composition comprising: (a) a nonionic surfactant with structure:
R.sup.2O(CH.sub.2CH(CH.sub.3)O).sub.3(CH.sub.2CH.sub.2O).sub.13H where R.sup.2 is a mixture of C.sub.8-C.sub.14 linear alkyl groups; and (b) glutaraldehyde; wherein a weight ratio of glutaraldehyde to nonionic surfactant is from 8:1 to 1:1.

6. A method for controlling the growth of microorganisms in an aqueous medium; the method comprising adding to the aqueous medium the synergistic microbicidal composition of claim 5.

Description

EXAMPLES

(1) Surfactants and biocides were evaluated for synergy by determining the synergy index (S.I.) of the combination. Synergy index was calculated based the concentration required to achieve a certain level of bacterial kill when the two antimicrobial compounds (A and B) alone and in combinations. The tests organisms were anaerobic sulfate-reducing bacteria (Desulfovibrio longus ATCC #51456), facultative bacteria Pseudomonas aeruginosa ATCC #10145 and Staphylococcus aureus ATCC #6538,
R.sup.2O(CH.sub.2CH(CH.sub.3)O).sub.3(CH.sub.2CH.sub.2O).sub.7HSurf. A
R.sup.2O(CH.sub.2CH(CH.sub.3)O).sub.3(CH.sub.2CH.sub.2O).sub.5HSurf. B
R.sup.2O(CH.sub.2CH(CH.sub.3)O).sub.3(CH.sub.2CH.sub.2O).sub.13HSurf. C
where R.sup.2 is a mixture of C.sub.8-C.sub.14 linear alkyl groups.

Example 1. Synergistic Effect of Glutaraldehyde and Surf A-C Against Anaerobic Sulfate-Reducing Bacteria

(2) Inside an anaerobic chamber (Bactron anaerobic chamber), a deoxygenated sterile salt solution (3.1183 g of NaCl, 1.3082 mg of NaHCO.sub.3, 47.70 mg of KCl, 72.00 mg of CaCl.sub.2, 54.49 mg of MgSO.sub.4, 172.28 mg of Na2SO.sub.4, 43.92 mg of Na.sub.2CO.sub.3 in 1 L water) was inoculated with Desulfovibrio longus ATCC 51456 to a final bacterial concentration of 10.sup.6 to 10.sup.7 CFU/mL. Aliquots of this cell suspension were then treated with glutaraldehyde, and each of Surf A-C at selected active concentrations. After incubation at 35 C. for 2 hours, viable bacteria in the aliquots were enumerated using serial dilution method. Synergistic combinations and their biocidal efficacy as well as Synergy Index were summarized in Table 1 to Table 3.

(3) The test results for demonstration of synergy of the combinations are shown in the tables below. Each table shows the results for combinations of two components against the microorganisms tested with incubation times; the end-point activity in ppm measured by the level of kill for compound A alone (CA), for component B alone (CB), and the mixture (Ca) and (Cb); the calculated SI value; and the range of synergistic ratios for each combination tested. SI is calculated as follows:
Ca/CA+Cb/CB=Synergy Index (SI)

(4) Wherein: Ca=Concentration of biocide A required to achieve a certain level of bacterial kill when used in combination with B CA=Concentration of biocide A required to achieve a certain level of bacterial kill when used alone Cb=Concentration of biocide B required to achieve a certain level of bacterial kill when used in combination with A CB=Concentration of biocide B required to achieve a certain level of bacterial kill when used alone
When the sum of Ca/CA and Cb/CB is greater than one, antagonism is indicated. When the sum is equal to one, additivity is indicated, and when less than one, synergism is demonstrated.

(5) TABLE-US-00001 TABLE 1 Biocidal efficacy of glutaraldehyde (Glut) and Surf. A against anaerobic sulfate-reducing bacteria, and Synergy Index Concentration (active ppm) for 99.99% bacterial kill Active weight in 2 hours Synergy ratio of Glut:Surf. A Glut Surf. A Index 1:0 13.2 0.0 17.1:1 8.8 0.5 0.67 11.4:1 8.8 0.8 0.67 3.4:1 8.8 2.6 0.69 1:3.4 8.8 29.6 0.96 0:1 0.0 >100

(6) TABLE-US-00002 TABLE 2 Biocidal efficacy of glutaraldehyde (Glut) and Surf C against anaerobic sulfate-reducing bacteria, and Synergy Index Concentration (active ppm) for complete bacterial kill Active weight in 2 hours Synergy ratio of Glut:Surf C Glut Surf C Index 1:0 29.6 0.0 8:1 13.2 1.6 0.46 6.7:1 13.2 2.0 0.46 5:1 19.8 4.0 0.71 3:1 13.2 4.4 0.49 1:1 13.2 13.2 0.58 0:1 0.0 >100

(7) TABLE-US-00003 TABLE 3 Biocidal efficacy of glutaraldehyde (Glut) and Surf. B against anaerobic sulfate-reducing bacteria, and Synergy Index Concentration (active ppm) for more than 99.999% Active bacterial kill weight ratio in 2 hours Synergy of Glut:Surf. B Glut Surf. B Index 1:0 29.6 0.0 17.1:1 19.8 1.2 0.68 11.4:1 19.8 1.7 0.68 7.6:1 19.7 2.6 0.69 3.4:1 19.7 5.9 0.73 0:1 0.0 >100

Example 2. Synergistic Effect of Glutaraldehyde and Surf. B Against Bacteria

(8) Sterile 0.85% NaCl solution was inoculated with approximately 10.sup.7 CFU/mL of Pseudomonas aeruginosa ATCC 10145 and Staphylococcus aureus ATCC 6538. Aliquots of the cell suspension were then treated with glutaraldehyde, and Surfs. A-D at selected concentrations. After incubating at 37 C. for 2 hr, viable bacteria in the aliquots were enumerated using serial dilution method. Synergistic combinations and their biocidal efficacy as well as Synergy Index* were summarized in Table 4.

(9) TABLE-US-00004 TABLE 4 Biocidal efficacy of glutaraldehyde (Glut), Surf. B against aerobic bacteria, and Synergy Index Concentration (active ppm) for more than 99.999% Active weight bacterial kill ratio of in 2 hours Synergy Glut:Surf. B Glut Surf. B Index 1:0 29.6 0.0 17.1:1 19.8 1.2 0.68 11.4:1 19.8 1.7 0.68 7.6:1 19.7 2.6 0.69 3.4:1 19.7 5.9 0.73 1:1 19.8 19.8 0.86 0:1 0.00 >100