Antimicrobials effectiveness

Pet Foods and Commercial Animal Feeds. Eor many years, it has been known that stable, long-shelf-life, intermediate-moisture pet foods can be prepared through the use of 0.1—0.3 wt % sorbates. In these products, the antimicrobial effectiveness of sorbates is enhanced by a combination of moderate heat treatment, pH adjustment, and reduced water activity via humectants such as propylene glycol, or by adjusting sugar and salt content. These techniques have been reviewed extensively (138,139). 

Astringents are designed to dry the skin, denature skin proteins, and tighten or reduce the size of pore openings on the skin surface. These products can have antimicrobial effects and are frequendy buffered to lower the pH of skin. They are perfumed, hydro-alcohoHc solutions of weak acids, such as tannic acid or potassium alum, and various plant extracts, such as bitch leaf extract. The alcohol is not only a suitable solvent but also helps remove excess sebum and soil from the skin. After-shave lotions generally function as astringents. 

Organic acids may inhibit growth when present in the undissociated form because of their abiHty to change the pH inside the ceU. The most efficient are benzoic acid and sorbic acid, but formic, acetic, and propionic acid also have this effect. The parabens, ie, -hydroxy benzoic acid esters, are also used because of their antimicrobial effect over a broad pH range. 

Relatively high levels of copper in pig diets can improve nutritional performance due to the antimicrobial effects in the gastrointestinal tract. However, if land is fertilized with dung from pigs and subsequently grazed by sheep, the sheep may suffer copper toxicity because of their increased susceptibility to copper compared with pigs. Similarly, pig diets would be unacceptable for sheep because of the high levels of copper therein. 

When examining this kind of data, one reahzes how difficult is to make general statements on the effects of chitosans on the cells another example is the antimicrobial effect of chitosans that varies with molecular size, degree of substitution and other parameters depending on the particular microorganism considered. 

Dykhuizen R., Frazer R., Benjamin N., Duncan C., Smith C.C., Golden M. and Leifert C. (1996). Antimicrobial effect of acidified nitrite on gut pathogens the importance of dietary nitrate in host defence . J Antimicrob Agents Chemothe, 40, 1422-1425. 

In the above trial [70] rifaximin was dissolved in chloroform and applied by repeated painting. After the solvent had dried a red sludge persisted over the dental structures allowing a continuous antimicrobial effect. Better delivery systems, such as subgingival controlled release preparations [12], are, however, needed to fully exploit the rifaximin potential in periodontal disease. In this connection, a gum-like device [71] has been developed that allows a controlled and continuous release of the antibiotic within the oral cavity. Large double-blind controlled trials using this and other formulations are now needed to establish the best therapeutic regimen for this indication. 

These tests would include compendial tests for Microbial Limits, Sterility, Bacterial Endotoxins, and Antimicrobial Effectiveness. 

The test for antimicrobial effectiveness is used to demonstrate the effectiveness of any added antimicrobial preservative(s). Compendial referenees include USP 24 Chapter (51) Antimicrobial Effectiveness Test JP XIII General Information 3, Pre-servatives-Effeetiveness Tests and the Ph. Eur. 3rd ed., Biologieal Tests, 5.1.3. Effi-eacy of Antimierobial Preservation. 

The selection of the preservative system for multiuse new products is the responsibility of the R D formulation group. Typical shelf specifications are 80 to 120% of label specifications. The appropriate preservative system for the particular formulation should be demonstrated to be effective by microbial challenge to at least 75% and preferably 50% of the target concentration. It is recommended that during development the product be formulated with preservative concentrations of 100, 75, and 50% of the labeled amount and be subjected to antimicrobial effectiveness testing to determine the lowest effective preservative concentration. 

The release and shelf-life specifications are established based on both the premarketed stability data for the preservative system concentration and the antimicrobial effectiveness test results. 

Abbreviations TAMC = total aerobic count TCYMC = total combined yeasts and molds AET = antimicrobial effectiveness test CCl = container-closure integrity A = water activity. 

A stability-indicating presrvative assay can be justified only at all time intervals as a substitute for the USP Antimicrobial Effectiveness Test by confirming preservative efficacy at 50, 75, and 100% of the lower shelf-life specification. 

If the study outlined above in paragraph 1 was not conducted during product development, it is recommended that QA and/or the technical services groups imder-take a study to justify the cmrent specifications and the elimination of routine antimicrobial effectiveness testing within the stability program. 

All preservative systems for both parenteral and nonsterile dosage forms should meet the 3 log reduction at 14 days for bacteria, that is, USP category I requirements. Both EP and BP Antimicrobial Effectiveness Testing would be run only if specially requested by the marketing group. 

USP 24 Testing Chapters (51) Antimicrobial Effectiveness Testing, (61) Microbial Limit Tests and (71) Sterility Tests, United States Pharmacopeial Convention, Inc., Rockville, MD, 2000. USP 24 Informational Chapters (1116) Microbiological Evaluation of Clean Rooms and other Controlled Environments, (1111) Microbiological Attributes of Pharmaceutical Articles, (1151) Pharmaceutical Dosage Forms, (1225) Validation of Compendial Methods, and (1231) Water for Pharmaceutical Purposes, United States Pharmacopeial Convention, Inc., Rockville, MD, 2000. 

The nitrogenous compounds produced in pepper fruit, which cause a burning sensation, are called capsaicinoids. Capsaicinoids are purported to have antimicrobial effects for food preservation [46], and their most medically relevant use is as an... 

Co-trimoxazole consists of trimethoprim and sulphamethoxazole combined because of their synergistic antimicrobial effects. Trimethoprim is a folate antagonist that poses a teratogenic risk. 

Haristoy X, Fahey JW, Scholtus 1, Lozniewski A. Evaluation of the antimicrobial effects of several isothiocyanates on Helicobacter pylori. Planta Med 71 326-330. 

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