US 5,206,151 AGranted

Rapid selection of biocide using a reduction oxidation indicator system

AssigneeNalco Chemical Company

InventorLinda R. Robertson

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Abstract

A rapid method for determining the minimum inhibitory concentration of biocides or biocidal agents for use in various microbiological contaminated aqueous systems is disclosed. This rapid technique provides for an opportunity to determine the minimum amount of anti-microbial agents, or biocides either singularly or combination, to control microbiological growth in aqueous streams contaminated by microorganisms. The test involves the use of reduction oxidation indicator dye systems which react to enhanced microbiological activity producing reducing enzymes such as dehydrogenase enzymes. The technique provides an answer within a time period of from about 30 minutes to about 8-10 hours as opposed to normal testing procedure that can require up to 1-2 weeks. The test procedures uses multiple columns of multiple sample wells on a microtitration plate and techniques for transferring prescribed aliquots of contaminated aqueous systems, nutrients, redox indicator dyes, and incremental and serially diluted concentrations of anti-microbial agents.

Claims11

Dependent claims

A method of determining the minimum inhibitory concentration of an antimicrobial agent in a contaminated aqueous system selected from the group consisting of stock or furnished solutions from a pulp and paper manufacturer, waters from open recirculating cooling water systems, waste effluent streams, chemical process streams and fermentation streams, which contain microbiological organisms, comprising the steps of:

(a) Obtaining a sample of said contaminated aqueous system;
(b) Adding a reduction oxidation indicator dye to said sample which reacts with microorganisms producing dehydrogenase enzymes;
(c) Adding dairy half and half creamer to said sample to form a dye treated nutrient aqueous system;
(d) Obtaining aliquots of the dye treated nutrient aqueous system;
(e) Performing multiple serial dilutions of an antimicrobial agent to be tested and forming mixtures of said aliquots of the dye treated nutrient aqueous system with each of the said serial dilutions;
(f) Incubating said mixtures at a temperature essentially equivalent to the temperature of the contaminated aqueous system for a period of time sufficient to develop the change in the dye color by the reaction of the dye with reducing enzymes;
and
(g) Determining the minimum inhibitory concentration of antimicrobial agent that inhibits those microbial organisms contained in said contaminated aqueous system by observing a change in color.

5 more elements

Dependencies are inferred from the claim text.