Title:  Control of microbial populations in the gastrointestinal tract of animals

United States Patent:  6,518,307

Issued:  February 11, 2003

Inventors:  McKenzie; K. Scott (Bryan, TX); Giletto; Anthony (College Station, TX); Hitchens; G. Duncan (Bryan, TX); Hargis; Billy M. (Fayetteville, AR); Herron; Kelly L. (Houston, TX)

Assignee:  Lynntech, Inc. (College Station, TX); The Texas A&M University System (College Station, TX)

Appl. No.:  981669

Filed:  October 17, 2001

The present invention provides a method for controlling microbial populations in the gastrointestinal tract of animals. The method comprises the step of orally administering an effective amount of a peracid to an animal. Percarboxylic acids useful in this invention include peracetic acid, perpropionic acid, perbutyric acid, peroctanoic acid, perglycolic acid, perglutaric acid, persuccinic acid, perlactic acid, percitric acid, perdecanoic acid or mixtures thereof. These percarboxylic acids have been found to provide good antimicrobial action with good stability in aqueous streams. In addition to peracetic, peroctanoic and perdecanoic, particularly preferred percarboxylic acids include perpropionic, perbutyric, perglycolic, perlactic and percitric acids.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method for controlling microbial populations in the gastrointestinal tract of animals. The method comprises the step of orally administering an effective amount of a peracid to an animal.

The term "animals" as used herein means humans and other vertebrate animals, including poultry, fish, cattle, swine, goats, lambs, dogs, cats, rodents, rabbits, birds, deer, non-human primates, and others.

If the peracid is to be delivered to a food animal for the purpose of preventing contamination of meat surfaces during slaughter, then it is preferred that the peracid is administered over a period just preceding slaughter.

The peracid is the reaction product formed by combining:

(i) an organic acid having one to eight carbon atoms;

(ii) an inorganic acid; and

(iii) an inorganic peroxide compound.

A method for controlling microbial populations in the gastrointestinal tract of animals, comprising the step of orally administering an effective amount of a compound having the formula: ##STR1##

where R is a group selected from alkyl, arylalkyl, cycloalkyl, aromatic or heterocyclic; and where n is one or more.

The peroxide of many organic acids have the attributes of hydrogen peroxide--effective germicidal and sterilizing capabilities, benign decomposition products, and infinite water solubility--but with greater lipid solubility and freedom from deactivation by catalase and peroxidases. The peroxide of acetic acid, peroxyacetic acid, or peracetic acid (PAA) is an effective biocide with no toxic residues and is widely used as a surface disinfectant in the food processing industry. PAA is a more potent antimicrobial agent than hydrogen peroxide alone, being rapidly active at low concentrations against a wide spectrum of microorganisms. It is sporicidal even at low temperatures and remains effective in the presence of organic matter. As a weak acid it is more active on the acid side but is germicidal with higher concentration in the alkaline range. Like hydrogen peroxide (HP), it is useful both in solution and as a vapor. These properties make it a remarkably valuable compound.

Peroxides in general are high-energy-state compounds, and as such can be considered thermodynamically unstable. PAA is considerably less stable than HP. 40% PAA loses 1 to 2% of its active ingredients per month, as compared with HP (30 to 90%), which loses less than 1% per year. The decomposition products of PAA are acetic acid, HP, oxygen, and water. Dilute PAA solutions are even more unstable: a 1% solution loses half its strength through hydrolysis in 6 days.

It may therefore be desirable for the practice of this invention to mix the components of the peracid or peroxygen solution at or near the location at which the biocidal solution is to be used. The individual componets may therefore be prepared commercially as separate containers or matched together such that the number of components for the final formulation is minimized but the stability of the precursor solutions is maximized. PAA is produced by the reaction of acetic acid or acetic anhydride with HP in the presence of sulfuric acid, which acts as a catalyst, as shown: ##STR2##

The oxidation of organic carboxylic acids with hydrogen peroxide and an inorganic acid catalyst is the best general method for the preparation of peroxy acids. The most common catalyst for aliphatic R in ##STR3##

is concentrated sulfuric acid. The reaction is an equilibrium and is driven to the right by removal of water or by the use of excess reagents. For aromatic R the best catalyst is methanesulfonic acid, which can be also used as the solvent.

Peroxygenated carboxylic acids have been shown to have excellent antimicrobial activity and have found utility in disinfecting diverse surfaces. These peroxy carboxylic acids are only moderately stable in aqueous solutions and therefore are most effective when used soon after the solutions are made. Examples of peroxygenated carboxylic acids include the following: performic, peracetic, perproprionic, peroxyheptanoic, peroxynonanoic, perlauric, monoperglutaric, diperglutaric, succinylperoxide, derivatives of perbenzoic acid, magnesium salt of peroxyphthalate, benzoyl peroxide, t-butylhydroperoxide, perlactic, percitric, perbutyric, peroctanoic, and perglycolic. Peroxygenated carboxylic acids are often known as, or referred to, by peracid compounds, peroxygen compounds, peroxo compounds and peroxides of organic acids.

Among other constituents, the invention comprises a carboxylic acid. Generally, carboxylic acids have the formula R--COOH wherein the R may represent any number of different groups including aliphatic groups, alicyclic groups, aromatic groups, heterocyclic groups, all of which may be saturated or unsaturated as well as substituted or unsubstituted. Carboxylic acids also occur having one, two, three, or more carboxylic groups.

Carboxylic acids have a tendency to acidify aqueous compositions in which they are present as the hydrogen atom of the carboxyl group is active. Therefore, the carboxylic acids may appear as an anion in solution. The carboxylic acid constituent within the present composition when combined with aqueous hydrogen peroxide generally functions as an antimicrobial agent as a result of the presence of the active hydrogen atom. Moreover, the carboxylic acid constituent within the invention maintains the composition at an acidic pH.

Carboxylic acids which are generally useful in the process of the invention are those which comprise percarboxylic acids. Percarboxylic acids generally have the formula R(CO₃ H)_n, where R is an alkyl, arylalkyl, cycloalkyl, aromatic or heterocyclic group, and n is one, two, or three, and named by prefixing the parent acid with peroxy.

Peracid powder disinfectants also useful in this invention can be derived from water plus mixtures of organic acid reservoirs (e.g., anhydrides, amides, and esters) added to hydrogen peroxide reservoirs (e.g., sodium peroxide).

While peroxy carboxylic acids are not very stable, their stability generally increases with increasing molecular weight. Thermal decomposition of these acids may generally proceed by free radical and nonradical paths, by photodecomposition or radical-induced decomposition, or by the action of metal ions or complexes. Percarboxylic acids may be made by the direct, acid catalyzed equilibrium action of 30-98 wt. % hydrogen peroxide with the carboxylic acid, by autoxidation of aldehydes, or from acid chlorides, and hydrides, or carboxylic anhydrides with hydrogen or sodium peroxide.

Percarboxylic acids useful in this invention include peracetic acid, perpropionic acid, perbutyric acid, peroctanoic acid, perglycolic acid, perglutaric acid, persuccinic acid, perlactic acid, percitric acid, perdecanoic acid or mixtures thereof. These percarboxylic acids have been found to provide good antimicrobial action with good stability in aqueous streams.

In addition to peracetic, peroctanoic and perdecanoic, particularly preferred percarboxylic acids include perpropionic, perbutyric, perglycolic, perlactic and percitric acids.

The process of the invention also uses a combination of peracetic acid with other percarboxylic acids, preferably, those named above and particularly, peroctanoic acid. This combination of percarboxylic acids has been found to provide preferred antimicrobial efficacy and stability in the presence of high organic loads. Generally, within the sanitizer, the concentration of, for example, peroctanoic acid may range from about 10 wt-% to 90 wt-% and preferably from about 10 wt-% to 20 wt-%. The concentration of peracetic acid may range from about 10 wt-% 90 wt-% and preferably from about 80 wt-% to 90 wt-%.

The process of the invention also uses peracetic acid. Peracetic acid is a peroxy carboxylic acid having the formula, CH₃ COOOH. Generally, peracetic acid is a liquid having an acrid odor at high concentrations and is freely soluble in water, alcohol, ether, and sulfuric acid. Peracetic acid may be prepared through any number of means known to those of skill in the art including preparation from acetaldehyde and oxygen in the presence of cobalt acetate. A 50% solution of peracetic acid may be obtained by combining acetic anhydride, hydrogen peroxide and sulfuric acid. Other methods of formulation of peracetic acid include those disclosed in U.S. Pat. No. 2,833,813, which is incorporated herein by reference.

In its most preferred embodiment, the process of the invention uses perlactic acid, CH₃ CH(OH)COOOH.

Generation of the peroxy acids may be accomplished in various manners known in the art. Specifically, the peroxy acids may be formed through the use of peroxy acid concentrate compositions. In such a case, the percarboxylic acid may either be generated naturally or through the combination of a hydrogen peroxide concentrate together with a carboxylic acid concentrate at the site of use such as that process which is disclosed in Lokkesmoe et al, U.S. Pat. No. 5,122,538, which is incorporated herein by reference. Furthermore, the peroxy acids may be formed by the methods disclosed in Lokkesmoe et al., U.S. Pat. No. 5,674,538, which is incorporated herein by reference.

Hydrogen Peroxide

The antimicrobial composition of the invention may also comprise a hydrogen peroxide constituent. Hydrogen peroxide in combination with the percarboxylic acid provides a surprising level of antimicrobial action against microorganisms despite the presence of skin, tissue and intestinal contents, mucose materials and membrane materials and sediment. Additionally, hydrogen peroxide may provide an effervescent action which may irrigate any surface to which it is applied. An additional advantage of hydrogen peroxide is that combinations of perlactic acid and hydrogen peroxide result in lactic acid, water, and oxygen upon decomposition all of which are food product compatible.

Generally, the concentration of hydrogen peroxide within the composition used in the process of the invention ranges from about 1 weight percent to about 50 weight percent, preferably from about 3 weight percent to about 40 weight percent, and most preferably from about 5 weight percent to about 30 weight percent. This concentration of hydrogen peroxide is most preferred as providing an optimal antimicrobial effect. These concentrations of hydrogen peroxide may be increased or decreased while still remaining within the scope of the invention.

Additives

The antimicrobial composition of the invention may also comprise any number of additives e.g. stabilizing agents, wetting agents, as well as growth factors, growth stimulants, vitamins, mineral supplements, antibiotics, drugs, and other nutrients that aid the growth and health of the animal receiving the formulation.

Stabilizing agents may be added to the composition of the invention to stabilize the percarboxylic and hydrogen peroxide formulation and prevent the premature oxidation of this constituent within the composition of the invention. Chelating agents or sequestrants generally useful as stabilizing agents include: alkyl diamine polyacetic acid-type chelating agents such as EDTA (ethylene diamine tetraacetate tetrasodium salt), acrylic and polyacrylic acid-type stabilizing agents, phosphonic acid, phosphonate-type chelating agents among others.

Preferable sequestrants include: phosphonic acids phosphonate salts including 1-hydroxy ethyldene-1, 1-diphosphonic acid (CH₃ C(PO₃ H₂)₂ OH), amino[tri(methylene phosphonic acid)] ([CH₂ PO₃ H₂ ]₂ (ethylene diamine[tetra methylene-phosphonic acid), 2-phosphene butane-1,2,4-tricarboxylic acid, as well as the alkyl metal salts, ammonium salts, or alkyloyl amine salts, such as mono, di, tri, or tetra-ethanolamine salts. The stabilizing agent is used in a concentration ranging from about 0 weight percent to about 20 weight percent of the composition, preferably from about 0.1 weight percent to about 10 weight percent of the composition, and most preferably from about 0.2 weight percent to 5 weight percent of the composition.

Also useful in the composition of the invention are wetting and defoaming agents. Wetting agents function to increase the penetration activity of the antimicrobial composition of the invention. Wetting agents which may be used in the composition of the invention include any of those constituents known within the art to raise the surface activity of the composition of the invention.

Along these lines surfactants, and especially nonionic surfactants, may also be useful in the present invention. Nonionic surfactants which may be useful in the present invention are those which comprise ethylene oxide moieties, propylene oxide moieties, as well a mixtures thereof, and ethylene oxide-propylene oxide moieties in either heteric or block formation. Additionally useful in the present invention are nonionic surfactants which comprise alkyl ethylene oxide compounds, alkyl propylene oxide compounds, as well as mixtures thereof, and alkyl ethylene oxide-propylene oxide compounds where the ethylene oxide-propylene oxide moiety is either in heteric or block formation. Further useful in the present invention are nonionic surfactants having any mixture or combination of ethylene oxide-propylene oxide moieties linked to a alkyl chain where the ethylene oxide and propylene oxide moieties may be in any randomized or ordered pattern and of any specific length. Nonionic surfactants useful in the present invention may also comprise randomized sections of block and heteric ethylene oxide propylene oxide, or ethylene oxide-propylene oxide.

Generally, the concentration of nonionic surfactant used in the invention may range from about 0 wt-% to about 5 wt-% of the composition, preferably from about 0 wt-% to about 2 wt-% of the concentrate composition, and most preferably from about 0 wt-% to about 1 wt-% of the composition.

The composition used in the process of the invention may also contain additional ingredients as necessary to assist in defoaming.

Generally, defoamers which may be used in accordance with the invention include silica and silicones; aliphatic acids or esters; alcohols; sulfates or sulfonates; amines or amides; halogenated compounds such as fluorochlorohydrocarbons; vegetable oils, waxes, mineral oils as well as their sulfated derivatives; fatty acid soaps such as alkali, alkaline earth metal soaps; and phosphates and phosphate esters such as alkyl and alkaline diphosphates, and tributyl phosphates among others; and mixtures thereof.

Especially preferable, are those antifoaming agents or defoamers which are of food grade quality given the application of the process of the invention. To this end, one of the more effective antifoaming agents comprises silicones. Silicones such as dimethyl silicone, glycol polysiloxane, methylphenol polysiloxane, trialkyl or tetralkyl silanes, hydrophobic silica defoamers and mixtures thereof may all be used in defoaming applications. Commercial defoamers commonly available include silicones such as Ardefoam.TM. from Armour Industrial Chemical Company which is a silicone bound in an organic emulsion; Foam Kill.TM. or Kresseo.TM. available from Krusable Chemical Company which are silicone and non-silicone type defoamers as well as silicone esters; and Anti-Foam.TM. ^RTM and DC-200^RTM from Dow Corning Corporation which are both food grade type silicones among others. These defoamers are generally present at a concentration range from about 0 wt-% to 5 wt-%, preferably from about 0 wt-% to 2 wt-%, and most preferably from about 0 wt-% to about 1 wt-%.

Food Agents

The formulation can contain flavoring agents, buffering agents and food preservatives: such as ascorbic acid, sorbic acid, citric acid, glutaric acid, phosphoric acid, and malic acid. These additives improve palatability and taste, thereby promoting consumption by the animals. These agents may also improve overall health and nutrition of the animals, as well as promoting further microbial destruction. Mineral salts may also be added. Glucose and sugars may also be added.

Generation of Peroxy Acids

The process of the invention may also be initiated through the use of peroxy acid concentrate compositions. In such a case, the percarboxylic acid may either be generated naturally or through the combination of a hydrogen peroxide concentrate together with a carboxylic acid concentrate at the site of use such as that process which is disclosed in Lokkesmoe et al, U.S. Pat. No. 5,122,538, issued Jun. 16, 1992, which is incorporated herein by reference.

Competitive Exclusion

The application of microorganisms as competitive exclusion microflora for the reduction of pathogen colonization in poultry has been discovered. Competitive exclusion microorganisms including Clostridium spp., Streptococcus faecalis, Bifidobacterium spp., and Bacteroides hypermegas have been examined. Furthermore, preparations containing several strains of single species, such as Bacteroides spp., Bifidobacterium spp., and Escherichia spp. have also been evaluated. Competitive exclusion diminish the populations of gram-negative enteropathogenic bacteria such as Campylobacter and Salmonella.

The method of this invention can also be applied in tandem with the addition of competitive exclusion microorganisms to the animal. The peroxygen formulation is added to destroy target pathogens, e.g., human enteropathogenic bacteria capable of colonizing poultry. Of particular interest are Salmonella and Campylobacter species. Competitive exclusion microorganisms can be introduced to the intestinal tract subsequently, allowing sufficient time for the active disinfection ingredients to dissipate. The intestines, now harboring reduced numbers of microbial pathogens are more capable of being colonized by the exclusion organisms.

Both peroxygen compounds and competitive exclusion microorganisms can be administered by oral gavage, in drinking water, in feed/foodstuffs, by spraying newly hatched chicks with an aqueous suspension, or a combination of the above. This combined treatment would preferably be performed early and as frequently as possible.

Claim 1 of 62 Claims

What is claimed is:

1. A biocide for ingestion by live animals, comprising:

an organic acid having one to eight carbon atoms;

an inorganic peroxide compound; and

at least one agent selected from wetting agents, stabilizing agents, defoaming agents, and combinations thereof.
 

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