How Antimicrobial Treatment Can Improve

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How Antimicrobial Treatment Can Improve Nonwovens By Steven F. Hayes and W. Curtis White Introduction We can safely say that microbial problems associated with nonwovens can be found in all segments of the nonwovens industry. Problems range from control of germs on surgical nonwoven fabrics, to control of microbial levels on wet wipes, filters, towels, baby diapers, and apparel fabrics. Problems show up in the form of degradation, defacement, odor, and health related problems. The need for con
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    How Antimicrobial TreatmentCan Improve Nonwovens BySteven F. Hayes and W. Curtis White  Introduction We can safely say that microbial problems associated with nonwovens can be found inall segments of the nonwovens industry. Problems range from control of germs onsurgical nonwoven fabrics, to control of microbial levels on wet wipes, filters, towels,baby diapers, and apparel fabrics. Problems show up in the form of degradation,defacement, odor, and health related problems. The need for controlling theseproblems, we can report, is evident in both the disposable and nondisposablesegments. Proper control of microbial levels is important to the safety and marketacceptance of the finished product.There are to be sure numerous ways to attack microbially related problems. Many timesthe problem can be eliminated by proper choice of fabric composition. Also, the use of sterilization procedures and barrier packaging has been widely employed to minimizemicrobial contamination. However, when these methods have not been appropriate,treatment of the fabric with an antimicrobial agent is an approach that has provensuccessful. Antimicrobials, we should note, can increase the value and performance of nonwovens,but inherent with antimicrobials are a variety of risks. Risks include environmental andmammalian toxicological concerns, need for broad-spectrum antimicrobial activity, andthe need for minimizing microbial adaptation.There are primarily two major classifications of antimicrobial agents available to thenonwovens industry. These include either the nonleachable or leachable types.Leachable antimicrobial agents are not chemically bonded with the fabric and can beremoved by contact with moisture. This paper describes the unique nonleachableSylgard (now known as the  ÆGIS Microbe Shield) treatment technology, itsperformance characteristics, safety, appropriate mill application techniques, currentuses, and its potential utility on the full spectrum of nonwoven products. Treatment The active ingredient of   ÆGIS Microbe Shield ™ treatment, as we describe, is3-trimethoxysilylpropyldimethyloctadecyl ammonium chloride. The  ÆGIS Microbe Shieldis a safe, broad spectrum, durable, nonleachable antimicrobial treatment. Datagenerated on nonwoven fabrics show that the product will control the growth of bacteria,fungi, yeasts, and algae on a treated surface. The organosilane referred to as AEM5700 ™ offers safety and efficacy advantages not found with traditional leaching types of antimicrobials. Durability Durability of an antimicrobial used in nonwovens is desirable for at least two reasons, aswe will demonstrate. The first of these reasons would be to provide antimicrobialprotection through an extended period of time. Many nonwovens have a long service lifeor are expected to function in conditions of high moisture. Value is added to thesenonwoven materials if the negative effects of microorganisms can be minimized.  The second reason is one of safety to man and the environment. In applications such assurgical drapes, it must be assured that materials coming from the drape do not causecytotoxicity or other negative effects on the patient. In other applications effects onnormal skin microbial flora and the skin irritating, sensitizing, or absorptive properties of the antimicrobial must be considered. The ultimate fate of the nonwoven goods and anyenvironmental impact also needs to be understood. The value of a bound antimicrobialis certainly understandable as one considers the above statements.The  ÆGIS Microbe Shield treatment is certainly durable and resistant to repeatedwashing, contact with body fluids, and abrasion. This durability exists because of theunique organosilane technology that utilizes two diverse technologies. Thetrimethoxysilyl functionality of the molecule has the ability to bond covalently to a varietyof receptive surfaces. The octadecylammonium chloride portion of the molecule offersionic bonding capacity and the antimicrobial activity. A variety of previously reportedpractical real world tests have been run to confirm the durability of this uniquetechnology. 1,2   Antimicrobial Activity To show the value of controlling microorganisms on nonwovens using the  ÆGIS  Microbe Shield treatment a variety of tests have been conducted. Tests include worksignificant to all components of the nonwovens industry (Table I). Although AEM 5700 isnot an efficient solution active antimicrobial, the obligatory Minimum InhibitoryConcentration (MIC) tests have been run. Results of these tests show clearly the broad-spectrum activity of the AEM 5700.The relevance of MIC data to use on fabrics is said to be hard to interpolate, soadditional studies were done using AATCC-100 Antimicrobials On Fabrics Test (TableII). The broad-spectrum antibacterial and antiyeast nature of AEM 5700 when bound totextiles is clearly demonstrated. An extension of this test was done by AmericanConverters. Documentation of their work was done using Scanning ElectronMicroscopy. The hollow appearance of the test organisms on the treated nonwovensurface after 15 minutes of exposure show clearly their nonviable condition.Many nonwovens, it is said, are subject to attack by defacing and deteriorating fungalattack. The relationship of allergenic response to fungal spores can also be linked tocontaminated surfaces. Data here show clearly the variety of fungi that can becontrolled by AEM 5700 treated fabrics.Using classical laboratory microorganisms provides valuable data, but does not projectto the real world conditions of a hospital, a diaper, or our homes. To more closelysimulate real world conditions, a modification of the AATCC-100 Antimicrobials OnFabrics Test was run. This test essentially utilized a series of clinical isolates rather thanlaboratory organisms. Results are clear in that control of these organisms wasconclusively demonstrated (Table IV).  To further extend the database on the antimicrobial activity of AEM 5700 treatednonwovens, a series of tests were taken to understand performance in medical/surgicalapplications. Body fluids, such as human sweat, defibrillated blood, whole blood, andirrigation fluids were tested. A microbial load was added to each of the test fluids andthen aliquots were applied to treated and control fabrics. Results were very uniform andconfirm that microbial loads from such fluids are readily controlled on AEM 5700 treatedsurfaces (Table V).Nonwovens treated with an antimicrobial agent are often expected to perform inambient conditions, according to the authors. The traditional unbound types of antimicrobials must have significant amounts of water present for them to manifest their antimicrobial activity. A test was undertaken where treated and untreated samples wererandomly placed in several environments. Retrievals show +95% reductions in microflora on the treated surfaces.To demonstrate the actual reduction of microorganisms during surgical procedures, American Converters has been conducting a study at Northwestern University. AnIso ã BAC ® surgical drape was prepared with treated and untreated areas within thefenestration. Retrievals were done after each surgical procedure. At this point in thestudy, 98 surgical procedures have been monitored. Differences between the retrievedmicro flora on treated and untreated areas have been consistently over 99%. Adaptation Study It has been observed in the Dow Corning laboratory that many traditional leaching typesof antimicrobial agents are susceptible to inductive or mutative adaptation. Adaptation isa phenomenon whereby a cell adjusts enzymatically (inductive) or genetically(mutational) to a toxicant in its environment. A study was undertaken with AEM 5700treated surfaces to determine the potential adaptation of Gram (-) and Gram (+)organisms after contact exposure. No increase in adaptive potential was noted after fivesuccessive exposures. This indicates an extremely low potential for adaptation (TableVI).Environmental safety testing results reveal:1. Low Solution Activity - AEM 5700 antimicrobial agent is designed to exhibit itsmaximum antimicrobial activity only when chemically bonded to a surface.Therefore it is not very effective just diluted in water.2. Reactivity to Surfaces - The chemistry of AEM 5700 antimicrobial agent is suchthat it rapidly exhausts from water solutions onto any solid material present in thesystem. This means that little if any waste material remains.3. Non-Leaching Character - Once AEM-5700 antimicrobial agent has come incontact with a surface, chemical changes occur which prevent it from beingsubsequently removed. Therefore, the material remains on the substrate anddoes not enter the environment.
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