Contaminated hospital surfaces are an important source of nosocomial infections. A major obstacle in marketing antimicrobial surfaces is a lack of efficacy data based on standardized testing protocols. Four clinical isolates were used: one Escherichia coli , one Klebsiella pneumoniae , and two Staphylococcus aureus strains. At 2 only ISO and 24 hours following inoculation, bacteria were collected from film surfaces and enumerated. Compared to untreated films in all protocols, there were no significant differences in recovery on either commercial brand at 2 or 24 hours after inoculation.
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The ASTM E method, titled "Determining the Antimicrobial Activity of Immobilized Antimicrobial Agents Under Dynamic Contact Conditions" is a sensitive test, often used to measure the antimicrobial activity of non-leaching, irregularly shaped or hydrophobic surfaces.
Microchem Laboratory finds the method to be far fetched as a model system, but we conduct it regularly anyway. Because it's one of the only ways to test an irregularly shaped antimicrobial object, such as a thread, powder, or 3D molded plastic in a standardized fashion. Though the ASTM E method has some drawbacks, it is relied upon heavily in the industry and can serve to benchmark your company's products against those offered for sale by other companies.
One aspect of testing " treated articles " which are normally exempt from EPA data review is that there is ample opportunity to develop scientifically defensible and realistic test models to verify antimicrobial efficacy. If your company's antimicrobial product or antimicrobial technology is particularly efficacious, we would love to talk with you about setting up a custom test that will help to differentiate your company's product in the marketplace.
Breadcrumb Home. ASTM E The concentration of the test microorganism is standardized. The microbial culture is diluted in a sterile buffer solution. For each product to be tested, 50 mL of the standardized microbial culture is placed into 3 containers sterile glass jars work well. One jar receives only bacterial suspension, another receives the antimicrobial test substance 1g or 4in 2 , and the last receives a control object an untreated object substantially similar to the test object, without the active ingredient.
Microbial concentration from the bacterial suspension only jars are enumerated at "time zero. Concentration of microorganisms in the jar that contained the antimicrobial product are compared to either the jar that contained only microbial suspension or the jar that contained the untreated control, depending on certain circumstances specified by the method.
A Solution Test is conducted per the method to determine leaching of the antimicrobial agent. The ASTM E method is written to allow experimental flexibility, which allows researchers to adapt the method to test antimicrobial products of various shapes and sizes. Weaknesses of the ASTM E Test Method Although this method is routinely used by manufacturers of antimicrobial surfaces, it is removed from actual usage of most antimicrobial products. The types of products commonly tested by this method include antimicrobial countertops, antimicrobial toilet seats, antimicrobial pens, or antimicrobial films.
In Microchem Laboratory's experience, many products that "pass" the ASTM E test do not produce an appreciable antimicrobial effect in more realistic situations such as when a dilute suspension of bacteria is placed directly on the product and then re-analyzed an hour later - often there is no difference between the "antimicrobial" sample and a negative control sample. An antimicrobial surface that "passes" at one hour of contact is almost certainly more effective than a surface that "passes" at 24 hours contact.
There is no clear criteria set by the method with respect to what constitutes "antimicrobial activity.
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Active view current version of standard. Other Historical Standards. Work Item s - proposed revisions of this standard. More E This dynamic shake flask test was developed for routine quality control and screening tests in order to overcome difficulties in using classical antimicrobial test methods to evaluate substrate-bound antimicrobials. These difficulties include ensuring contact of inoculum to treated surface as in AATCC , flexibility of retrieval at different contact times, use of inappropriately applied static conditions as in AATCC , sensitivity, and reproducibility. This standard does not purport to address all of the safety concerns, if any, associated with its use.
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The Activity of Antimicrobial Surfaces Varies by Testing Protocol Utilized
Historical Version s - view previous versions of standard. Work Item s - proposed revisions of this standard. More E This test method ensures good contact between the bacteria and the treated fiber, fabric, or other substrate, by constant agitation of the test specimen in a challenge suspension during the test period.