Document ID: EPA-HQ-OPP-2016-0467-0014
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2016-08-10T04:00Z

Sehulster Responses

 Suitability of the Protocol:  The protocol has been revised to include additional methodology for preparing the test microbe, chemical and physical abrasion, details on materials and supplies, and quality control practices. Refer to Appendix A for an overview of the protocol changes. Please comment on the following issues:   
 Do the revisions summarized in Appendix A provide a substantial improvement and technically sound approach for testing the antimicrobial properties and product durability of solid copper/copper alloy materials?  If not, please provide advice on any additional elements that should be addressed or modified.

The modifications as outlined in Appendix A seem reasonable and provide some needed clarifications.  I have a question about the preparation of the carriers.  In the protocol it is stated that flaming, autoclaving, or using UV light is not recommended for carrier sterilization because of possible adverse effects on the carriers.  Has the use of a dry heat oven been ruled out at well?  I'm concerned that simple immersion in alcohol for a short period of time may not be a satisfactory alternative to a physical method of sterilization.
 
 Is the protocol of sufficient detail so that it may be conducted by a qualified testing laboratory and is likely to result in reproducible results when conducted in different testing facilities and/or at different times within the same laboratory?  If the protocol is not of sufficient detail, which areas require improvement?

Knowing the meticulous approach EPA uses for method development, I'm assuming the agency has conducted the intra-laboratory and inter-laboratory validation testing for the method.  If they have completed this phase of development, then I would be confident that the method can be performed reliably in a responsible testing laboratory.  There is one aspect of the protocol that concerns me, and that is the allowance of what could be a great deal of variability in materials, especially for the carrier materials.  The protocol indicates that descriptions must be entered into the results record, but does the agency have confidence that the reported culture results are accurate and valid, given the potential variability?  It would seem to me that the agency should specify the carrier materials so that all the labs would be using the same materials, thereby eliminating one major variable in the analysis of the results.
   
 Is the protocol suitable for evaluating the antimicrobial efficacy of solid copper/copper alloy materials, as well as copper-impregnated or coated surface materials?   If the protocol is not suitable for one or both, please provide advice on how to modify the protocol to cover both materials.

In my opinion, I would separate the testing of spray-on copper products from the copper-clad materials.  Statement #10 (under A. Carriers) is the statement of asking the lab to provide the agency with the details about the surfaces used for the spray-on product testing.  I see too much potential variation here.  In my opinion, I would suggest that the agency specify three or four standard materials (e.g., stainless steel, plastic, glass, a painted surface, etc.) and direct the labs to spray the copper product onto these standard materials as carriers and proceed with testing, including the necessary controls.  In addition, I would think that the agency would want to know how durable the antimicrobial properties are for spray-on products.  Can the product be "recharged" in some fashion, or must the product be re-applied?

One question  -  how does use of a spray-on copper product relate to EPA's Treated Article Exemption?  The whole purpose of a spray-on product under these circumstances would be to apply an antimicrobial residual to a surface in efforts to reduce microbial pathogen spread to and transfer from hard surfaces.  Is a sprayed surface to be tested for antimicrobial efficacy in a laboratory adequate to meet the criteria in this part of FIFRA? 
     
 There is an interest in using the protocol to evaluate other types of hard non-porous surfaces impregnated with antimicrobial agents other than copper (other solid metals, metal alloys, fabricated materials etc.).  Is the protocol suitable for testing the antimicrobial activity of other types of hard, non-porous surfaces treated or impregnated with antimicrobial agents?  If not, please explain why and offer advice on how to change the protocol so that it would produce reliable, reproducible results when testing these other surface types.

By saying "there is interest..." it's evident that the agency has not moved in this direction as yet.  The current protocol could be used to start the validation process, but as it stands now  -  no  -  there's a great deal more work to be done.  All the details of the experimental methods would need to undergo validation, complete with intra-lab and inter-lab testing.  It is possible that the method might need to be adjusted or revised as a result of the validation process.  Detailed descriptions of materials, experimental conditions (e.g., temperature, relative humidity, etc.), recommended suppliers of carrier materials, etc. would need to be included.  The challenge bacteria would have to be evaluated to determine if they are suitable.

 Controls:  Stainless steel was selected as the control carrier material due to the inert nature of the material.  The final log reduction values are calculated by taking the log 10 difference between the stainless steel control carriers and the product test carriers.
 In the protocol, the stainless steel control carriers are not subjected to the mechanical surface abrasion or the chemical treatments (A, B, and C). Please comment on the suitability of this approach.  If this approach is not appropriate, please provide advice on how to address the management of the control carriers.

In my opinion, you should limit the differences between controls and test carriers as much as possible, leaving that which is to be tested the only difference.  I think it would be important to include control carriers that have been subjected to the abrasion and chemical treatments.
 
 Please comment on whether the comparative analyses of log reduction values (i.e., the difference in the level of microbes on exposed carriers vs. unexposed carriers and stainless steel control carriers) is a technically sound approach to the assessment of the antimicrobial activity of the copper and copper alloy products.

In my opinion, I think the agency should continue to use the analyses of log reduction values as the description of the efficacy of the product.  This will help the manufacturers market their product to the customers  -  healthcare facilities.  The infection prevention nurses and environmental services directors/supervisors are familiar with this expression of potency and will be looking for this information on the product literature and basing their decision on this property (not to mention the cost).

 Contact Time:  EPA's current guidance requires that a hospital disinfectant kill between five to six logs (100,000 to 1,000,000) of the target microbe in a qualitative test system within the time frame specified on the product labeling.  The use of copper and copper alloy products in medical care facilities is a supplement to (not a replacement for) standard infection control practices and use of EPA registered hospital disinfectants.  
 In a standard chemical disinfectant test, the microbe is applied to the carrier surface, allowed to dry, and then exposed to the disinfectant.  The contact time for the chemical disinfectant begins upon application of the disinfectant.  For copper and copper alloy materials, the surface serves as the antimicrobial agent.  The protocol specifies that the contact time begin upon application of the microbe to the surface, not after the microbe has dried on the surface.  Please comment on whether it is appropriate for the contact time to begin upon inoculation of the surface, and if not, please offer alternative approaches for this step in the protocol.

In my opinion, the answer to this question is yes.  From my perspective, the whole rationale for having copper-clad items is/was to continually inactivate microorganisms, albeit on a lower level compared to a disinfectant, but the use of these surfaces does not eliminated the requirement that healthcare facilities continue with their routine surface disinfection.  With regards to starting the clock with the application of the challenge bacteria as opposed to allowing the inoculum to dry, this approach mimics a real situation.  Bacteria in droplets, moisture from the hands, etc. would be most likely to make initial contact with these and other surfaces.
   
 Please comment on whether a single inoculation per carrier (4-5 logs bacteria per carrier) for both Staphylococcus aureus and Pseudomonas aeruginosa provides adequate challenge to evaluate the level of antimicrobial activity.  A soil load (three-part) is also added to the inoculum before carrier inoculation.  If a single inoculation is not appropriate, explain why and provide suggestions on how to improve the inoculation procedure.

This is an interesting question, given it's been the agency's standard protocol to use the separate challenge approach (I.e., one genus/strain of bacteria as the challenge for each experiment).  While a mixed culture might be closer to the reality of what's on a hard surface in a real life setting, this still represents a major departure from agency protocol.  In addition, the vast majority of researchers use pure cultures for their experiments, not mixed cultures.  If you were to incorporate a mixed culture as the challenge inoculum, you would have to repeat basically all of the validation experiments to ensure that this does not generate problems that would interfere with the analyses and interpretation of the results.  What is your confidence level regarding the preparation of the mixed culture?  Would you use equal concentrations of each bacteria or more of one and less of the other?  Going with a mixed culture means another round of validation studies.
   
 Based on the Agency's experience in utilizing hard non-porous carriers in standard efficacy test methods, microbial populations on environmental surfaces decline naturally over time mainly due to desiccation.  This natural decline presents challenges in determining whether the decline in a microbial population is due to desiccation or antimicrobial activity. An antimicrobial surface such as copper should be capable of accelerating the decrease in the number of surface-associated bacteria.  The Agency expects that an antimicrobial effect due to the product should be measureable within a one hour timeframe. The original protocol specified a 99.9% reduction of viable bacteria within two hours of inoculation while the new protocol specifies a one hour timeframe.   Please comment on the suitability of reducing the timeframe from two hours to one hour, or if the specified timeframe is not reasonable, provide advice on a suitable timeframe.

Going with a one-hour contact time as opposed to a two-hour contact time signifies to me that the agency is expected a greater, more efficient antimicrobial effect with the current copper products.  I'm assuming the manufacturer of the copper has published evidence that the product achieves several log reductions in as little as one hour.  Experiments depicting inactivation over time elapsed will confirm this.  I don't envision a problem with setting the contact time at one hour.  In real life uses, however, the antimicrobial activity of copper is expected to be continual, so at any given time there will be numbers of inactivated microorganisms on a surface and numbers of live, freshly deposited microorganisms that will soon become inactivated.
         
 Please comment on whether copper and copper alloy products that kill 99.9% of target microbes within 1 hour would provide a significant benefit in reducing levels of target microbes in medical care facilities.  If you think that killing 99.9% of target microbes within 1 hour would not provide a significant benefit in reducing levels of target microbes in medical care facilities, please offer advice on the level of antimicrobial activity that would provide such benefits.  Please explain the basis for your conclusions.

Another interesting question.  I think the presence of a continual sanitizing property on a surface would be very beneficial to healthcare facilities, but the real proof of this would come from a well-designed epidemiological study that documents a reduction in healthcare-associated infections.  Such a study should be a prospective study that carefully identifies potential confounding variables and controls for them.

At one point in an EPA conference several years ago, manufacturers noted that the levels of microbial contamination on most hard surfaces was less than 10[6] per unit area, and they asked the question  -  why do we have to prove a 6 log reduction for their product to be registered.  Many manufacturers indicated that if they could promote sanitizers for hard surfaces in hospitals, the contact times would shorten significantly.  Perhaps the copper surfaces brings this debate to the forefront.   

 Abrasion/Chemical Treatment: The proposed protocol includes a requirement that the carriers made from the copper or copper alloy undergo both an abrasion step and a chemical treatment step in order to simulate actual conditions of use and to evaluate how abrasion and/or chemical treatment might affect the level of antimicrobial activity.  Note that some disinfectant and sanitizer products, as well as some cleaning agents, contain chelating agents (e.g., EDTA) intended to bind free metal ions.  
 Please comment on whether abrasion and/or chemical treatment is likely to affect the level of antimicrobial activity displayed by a product.  If not, please explain why.  If so, please comment on how well the proposed abrasion step and chemical treatment step reflect the likely range of actual use conditions.  To the extent that the simulated conditions do not reflect the likely range of actual use conditions, please comment on whether the additional requested information (quantitative and qualitative) about the durability of the product is sufficient to assess the potential for physical disruption of the product surface after long term use.

A surface that is no longer smooth can provide topography that may shield microorganisms present in the cracks, etc. from full contact with the antimicrobial product, in essence resulting in a diminished antimicrobial result.  With a copper-clad surface, this diminishing result could be avoided if the copper layer is deeper than the superficial rough surface.  If the cracks and depressions in the surface extend beyond the depth of the copper layer, we would expect that the performance of the product will be diminished.  

Since the incorporation of an abrasive and chemical treatment represents a departure from a more traditional method of evaluating a product's antimicrobial properties,  I think the agency should ask for as much manufacturer information about the physical durability of the product, both copper-clad and spray-on versions, as can be provided.  In addition, the agency should pose the durability question to the manufacturers of steel surfaces and equipment for comparison.  Somewhere between these two pieces of information you should get a reasonable idea of the wear-and-tear of hospital surfaces and how quickly this occurs.  What evaluation did you use to shorten the abrasive and chemical treatment time as described in your document?
     
 If you think that abrasion and/or chemical treatment may affect antimicrobial efficacy, but that the proposed protocol does not adequately evaluate the potential for such effects, please offer advice on how to change the protocol (e.g., what process and/or chemical solutions should be used to treat a carrier) so that the protocol will adequately evaluate the level of antimicrobial activity of a product.  Please comment specifically on whether the use of products containing chelating agents is likely to affect the level of antimicrobial activity of solid metal and metal alloy products. Also, please comment specifically on whether the cleaning step (thoroughly rinse with DI water) between exposure cycles is sufficient to remove residual chemical solutions (solutions A, B and C).

I think the inclusion of the abrasive and chemical treatment in the protocol is appropriate, but it would be important to know how thick the copper layer is.  A rough surface that is still copper-clad would still have antimicrobial activity, but if the cracks and crevices get down to base metal that could diminish the antimicrobial activity.  Furthermore, the deeper the cracks and crevices, the more likely you will have the opportunity for soil levels to build, thereby adding another factor to protect microbes.  With regards to the presence of chelating agents, I know they do have an effect on metal ions in solution, in essence removing them from solution, but I do not know much about their action on metal ions in hard metal.  With regards to whether or not the use of water to thoroughly rinse the chemicals away from the carriers is effective, my sense is that this rinse step should be adequate.  If the question involved the presence of soil or organic matter on the surface, then I would think that a surfactant would be needed.

All of this discussion about abrasive and chemical treatment center on the copper-clad surfaces and items.  With the spray-on products, I would think the manufacturers would have to advise their customers to reapply the product frequently to counter surface abuse over time.  How long does the effect remain active after the spray-on product is applied?  It would seem to me that any physical or chemical abuse to the treated surface would remove the product from the surface.    

 Residual/Continuous Activity:  Residual/continuous activity over time is claimed to be one attribute inherent to copper and copper alloy products.  
 Some technology developers would like to claim that solid copper and copper alloy products provide "residual/continuous activity."  Please comment on whether the proposed protocol is capable of determining if copper and copper alloy products provide such activity, and if not, what changes to the proposed protocol (e.g., instituting repeated inoculations of the carrier) would provide data to evaluate such activity.

If the manufacturer is claiming antimicrobial action over time, then a protocol would need to be developed to evaluate this.  I don't think the current protocol lends itself to measuring a continual action.  One problem to be addressed is this - is there an endpoint for a protocol that attempts to validate "continual" activity?

In my opinion, before the agency can develop a test protocol for continual antimicrobial action, it should spend some time to establish a definition for this phenomenon, and propose it as part of the pesticide registration regulatory program after a Federal Register comment period.  Once you have defined the property and established measureable, discreet aspects to that property, then you can develop a method to measure and validate this.