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By Sheryl Lindros Dolan and Heather F. Collins, M.S.

On September 29, 2017, the U.S. Environmental Protection Agency (EPA) announced the availability of two final test method Standard Operating Procedures (SOP) for evaluating the efficacy of antimicrobials against spores of Clostridium difficile (C. diff)

EPA also released regulatory guidance for test criteria and pesticide claims for these products, specifically “Methods and Guidance for Testing the Efficacy of Antimicrobial Products Against Spores of Clostridium difficile on Hard Non-Porous Surfaces.”  EPA states that these test methods and guidance “provide a framework for registrants who seek to make a claim for antimicrobial pesticide products to control C. difficile spores on hard, non-porous surfaces.”

C. diff is an anaerobic, spore-forming bacterium and a frequent cause of hospital-acquired infections.  The spores survive on hard surfaces such as glass, metals, and plastics that are commonly found in health-care settings.  Hospitals and other health care facilities often use antimicrobial pesticides to reduce the number of spores on environmental surfaces.  Registrants seeking antimicrobial product registrations with claims to control C. diff will need to carefully review these documents as they consider the efficacy data that EPA will likely require to support these claims, as well as the claims that can be made and supported for these products.

EPA MLB SOP MB-28 describes the test methodology for producing and storing standardized spore suspensions of C. diff based on ASTM E2839, Standard Test Method for Production of C. difficile Spores for Use in Efficacy Evaluation of Antimicrobial Agents (ASTM International).  A spore suspension should be developed and qualified according to EPA MLB SOP MB-28 before an efficacy evaluation can be performed using method EPA MLB SOP MB-31.  EPA MLB SOP MB-31 describes a quantitative method intended for evaluating the sporicidal efficacy of liquid disinfectants against spores of C. diff on inanimate, hard, non-porous surfaces. 

EPA solicited comments on the clarity of the test method SOPs and the regulatory guidance in December 2016.  EPA received comments from 12 entities.  The primary areas of comment included the following:

  • Test carrier interaction;
  • Additional method validation;
  • Verification testing;
  • Soil load;
  • Use of a standard setting organization to publish test methods;
  • Proposed revisions to the guidance document; and
  • Proposed revisions to the standard operating procedures.

EPA revised the drafts to incorporate suggested changes.  EPA posted its response to those comments in Docket No. EPA-HQ-OPP-2016-0753-0026

Some of the changes to the guidance document based on submitted comments include clarifying:

  • Three batches of test product should be tested on independent test days;
  • The inclusion of the three-part soil load is used for all test, control, and test system control carriers; and
  • The current document supersedes the previous 2014 guidance document.

The new guidance proposes updated standard label claims and special instructions that are intended to provide greater clarity to the user community.

EPA’s response to comments and other documents associated with this action are available in Docket No. EPA-HQ-OPP-2016-0753 at www.regulations.gov.  The methods and guidance also are found on EPA’s Antimicrobial Testing Methods & Procedures Developed by EPA's Microbiology Laboratory webpage, at the Methods tab as Method IDs MB-28 and MB-31, and at the Guidance tab as Sporicidal Claims Against Clostridium difficile.

Commentary

C. diff is widely recognized as one of the most common causes of healthcare-acquired infection.  C. diff infections, spread by transmission of bacterial spores, have proven difficult to prevent.    EPA’s new guidance and test methods are intended to clarify the efficacy standards that pesticide products claiming to reduce C. diff spores must meet, as well as the associated claims that can be made.  This guidance should bring more clarity to pesticide registrants seeking to register such products and to healthcare facilities in their identification of registered pesticide products that may help them to reduce C. diff spores and thus help with prevention efforts. 


 

By Sheryl L. Dolan and Margaret R. Graham

On August 1, 2017, the U.S. Environmental Protection Agency (EPA) announced the availability of two final test method Standard Operating Procedures (SOP) for evaluating the efficacy of antimicrobial pesticides against two biofilm bacteria, Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus):

EPA also released regulatory guidance for test criteria and pesticide claims for these products, specifically Guidance for Testing the Efficacy of Antimicrobial Products Against Biofilms on Hard, Non-Porous Surfaces.  Drafts of the SOPs and the guidance were initially released in October 2016 for comment.  EPA received comments from nine entities and revised the drafts to incorporate suggested changes.  EPA posted its response to those comments in Docket EPA-HQ-OPP-2016-0357

EPA states that the two methods are adapted from ASTM International (ASTM) standard methods.  EPA MLB SOP MB-19 is used to generate the P. aeruginosa or S. aureus biofilm on coupons.  EPA MLB SOP MB-20, the Single Tube Method, then is used to determine the effectiveness of an antimicrobial product in reducing bacteria in biofilm on the coupons. 

Notable aspects of the test criteria and claims guidelines include:

  • The mean log density for the test organisms of 8.0 to 9.5 for P. aeruginosa and 7.5 to 9.0 for S. aureus; and
  • Product performance criterion of a minimum 6-log reduction.

The guidance lists several examples of claims for efficacy against public health biofilm that EPA states are acceptable.

EPA MLB SOP MB-20 is designed to evaluate the efficacy of antimicrobial products that are water soluble powders or liquid formulations.  If a company wishes to test a different type of product formulation, or test different target microorganisms, or make any other proposed modifications, it would be well advised to submit proposed alternatives to EPA for review and approval.  EPA specifically cautions that the current methodologies are intended for data development to support claims for products registered for use on hard, non-porous surfaces and are not suitable for use sites associated with water systems.

The EPA’s Office of Pesticide Programs’ (OPP) regulation of biofilms has been the subject of increasingly intense commercial interest for years and the availability of this testing guidance is welcome news.  While not all will agree with the approach, the new guidance is a helpful addition to OPP’s testing guidance portfolio.  

More information on antimicrobial pesticides is available on our blog under key phrase Antimicrobial Pesticide.  More information on the methods and guidance is available on EPA’s website and in Docket No. EPA-HQ-OPP-2016-0357.


 

By Lisa M. Campbell, Lisa R. Burchi, and Margaret R. Graham

The U.S. Environmental Protection Agency (EPA) has recently announced the availability of two proposed test methods and associated testing guidance for evaluating antimicrobial pesticides against two biofilm bacteria, Pseudomonas aeruginosa and Staphylococcus aureus, for comments.  EPA states that registrants of antimicrobial products with public health claims are “required to submit efficacy data to EPA in support of the product’s registration” under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).  EPA is soliciting comments on the clarity of the standard operating procedures and the regulatory guidance.  The two test methods are:

The Draft Guidance to Assess the Efficacy of Antimicrobial Pesticide Products Intended to Control Public Health Biofilms on Hard, Non-Porous Surfaces describes biofilms and their public health significance; the two test procedures for developing efficacy data supporting biofilm claims; products that may be eligible for biofilm claims; test criteria; data submission procedures for efficacy data; and labeling guidance.

The draft guidance states that the term biofilm “is reserved for claims against biofilm that contain specific bacteria that are directly or indirectly infectious or pathogenic to humans,” and “biofilm claims are considered to be public health claims for which the agency must review and approve appropriate efficacy data.”  EPA states: “Examples of use sites that may be supported by the biofilm test methodologies herein, and found acceptable, include restrooms, shower stalls, sink basins or drains (excluding the drain pipe) and nearby hard, non-porous surfaces of walls, countertops, and instrument trays in patient care areas of hospitals.  In contrast, claims against non-public health slimicides must also be supported by appropriate efficacy data, however, submission of the data is only required when requested by the EPA.” 

The Draft Guidance also sets forth examples of acceptable label claims against public health biofilms and acceptable non-public health claims.  The examples of acceptable label claims against public health biofilms are:

  1. Kills 99.9999% of bacteria* in biofilm on a hard, non-porous surface;
  2. Kills a minimum of 99.9999% of bacteria* in biofilm;
  3. Reduces at least 99.9999% of bacteria* growing in biofilm;
  4. Formulated to kill 99.9999% of bacteria* in biofilm;
  5. Other related claims:
  • Kills biofilm bacteria*; and
  • Penetrates biofilm, killing the bacteria* living there.

*[List of bacteria “tested as a biofilm”; at a minimum, Pseudomonas aeruginosa and Staphylococcus aureus].

Examples of acceptable non-public health claims supported by appropriate efficacy data include:

  • Slimicide;
  • Cleans away microorganism slime/grunge;
  • Maintains control of slime; and
  • Controls slime-forming microorganisms.

Comments will be accepted until December 5, 2016.