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Did You Know the Environmental Protection Agency (EPA) has Made Some Changes on How to Test Against Spores of Clostridium difficile?

By: Danina Rinaldi

Established in 1970, the Environmental Protection Agency (EPA) is purposed to protect human health and the environment.  One of the responsibilities of the EPA is to provide guidance on how to evaluate products in the marketplace with claims.  One of those claims is for hard non-porous surface antimicrobial product and its efficacy against a spore known as Clostridium difficile.

The new guidance would be effective September 2017 and is applicable to any product such as liquids, sprays or towellete formulations for sterilants, sporicides or hospital disinfectants.  For each of these products, the appropriate amount of liquid must be tested against C. difficile.  In the case of towelletes, the liquid expressed from the towellette is tested, in addition to the amount remaining on the hard non-porous surface treated/wiped with the towelette, per instructions after use.  In addition, visual and gravimetric wetness tests should be performed.

A general summary of the test includes testing three test batches at the lower certified limits (LCL) on three independent days.  Ten carriers are to be evaluated against the product, three test system control carriers and three unexposed carriers as controls in each test.  The test system control carriers are now to be performed on Sodium Hypochlorite (NaOCl).  The previous guidance used Hydrogen Chloride (HCl).  The contact time for efficacy testing should not exceed 10 minutes.

The EPA provides procedures readily available for review on their website.  These procedures must be followed in order for submission acceptance.  Applicants can also propose to the Agency alternate procedures or practices, however this must be done in advance and prior to testing.


Test Procedures for Developing Efficacy Data Supporting C. difficile Claims:

  • EPA MLB SOP MB-28– “Production and Storage of Spores of Clostridium difficile for Use in the Efficacy Evaluation of Antimicrobial Agents,” adapted from ASTM standard method E2839-11.
  • EPA MLB SOP MB-31– “OECD Quantitative Method for Testing Antimicrobial Products against Spores of Clostridium difficile on Inanimate, Hard Non-porous Surfaces,” adapted from the OECD Guidance Document, dated June 21, 2013.
  • EPA MLB SOP MB-28– is used to produce spores of C. difficile. The spores are used in the procedure described in EPA MLB SOP MB-31 to determine the effectiveness of the antimicrobial product.

If you have not tested your products according to the new EPA guidelines or would like to add this claim, contact us today.  The microbiology and chemistry department at Gibraltar Laboratories performs this testing on a routine basis.