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.1O(CH.sub.2CH(CH.sub.3)O).sub.5(CH.sub.2CH.sub.2O).sub.6H where R.sup.1 is 2-ethylhexyl; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 8:1 to 1:1.

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

3. A synergistic microbicidal composition comprising: (a) a nonionic surfactant with structure:
R.sup.1O(CH.sub.2CH(CH.sub.3)O).sub.5(CH.sub.2CH.sub.2O).sub.9H where R.sup.1 is 2-ethylhexyl; and (b) glutaraldehyde; wherein a weight ratio of the glutaraldehyde to nonionic surfactant is from 8:1 to 1:4.

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

Description

EXAMPLE

(1) Surfactants and biocides were evaluated for synergy by determining the synergy index (S.I.) of the combination. Synergy index was calculated based on the concentration required to achieve a certain level of bacterial kill when the two antimicrobial compounds (A and B) alone and in combinations. The test organism was anaerobic sulfate-reducing bacteria Desulfovibrio longus ATCC #51456.
Surf. A R.sup.1O(CH.sub.2CH(CH.sub.3)O).sub.5(CH.sub.2CH.sub.2O).sub.6H
Surf. B R.sup.1O(CH.sub.2CH(CH.sub.3)O).sub.5(CH.sub.2CH.sub.2O).sub.9H
where R.sup.1 is 2-ethylhexyl.

Example: Synergistic Effect of Glutaraldehyde and Surf A and B 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 and B 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 and Table 2.

(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 Active weight ppm) for complete ratio of bacterial kill in 2 hours Synergy Glut:Surf. A Glut Surf. A Index 1:0 13.2 0.0 8:1 8.8 1.1 0.68 6.7:1.sup. 5.9 0.9 0.45 5:1 5.9 1.2 0.46 3:1 3.9 1.3 0.31 1:1 3.9 3.9 0.34 0:1 0.0 >100

(6) TABLE-US-00002 TABLE 2 Biocidal efficacy of glutaraldehyde (Glut) and Surf. B against anaerobic sulfate-reducing bacteria, and Synergy Index Concentration (active Active weight ppm) for 99.99% ratio of bacterial kill in 2 hours Synergy Glut:Surf. B Glut Surf B Index 1:0 5.9 0.0 7.6:1.sup. 3.9 0.5 0.67 3.4:1.sup. 3.9 1.2 0.67 1:1 3.9 3.9 0.70 .sup.1:3.4 3.9 13.2 0.79 0:1 0.0 >100