Candida auris is an emerging, often multidrug-resistant yeast that has caused severe healthcare outbreaks in recent years. The fungus survives on surfaces and spreads easily in hospitals and long-term care facilities. In the United States, clinical cases of C. auris have risen sharply (4,514 new cases in 2023), and its infections are associated with high mortality – roughly one-third of hospitalized patients die due to multidrug-resistant C. auris infections. These statistics highlight the huge impact of this pathogen on already vulnerable patients.

To control C. auris, the Centers for Disease Control and Prevention (CDC) and the U.S. Environmental Protection Agency (EPA) recommend maintaining strict environmental hygiene. The CDC advises thorough daily and post-discharge cleaning of hospital rooms and medical equipment using EPA-registered hospital disinfectants with exclusively C. auris (List P) or C. difficile (List K) claims. In response, the EPA has issued guidance to help disinfectant manufacturers generate robust efficacy data for such claims through rigorous antifungal disinfectant testing. This guidance ensures that disinfectants marketed for C. auris control truly meet the said standards.

EPA Guidance on Efficacy Testing of Disinfectants Against C. auris

Purpose of the Guidance 

The sole purpose of EPA’s guidance is to outline how to conduct strict Candida auris testing for hospital-grade disinfectants (and related antimicrobial products). It applies to products used on hard, non-porous surfaces in healthcare settings. The goal is to provide standardized antifungal disinfectant testing methods so that products claiming C. auris efficacy are backed by scientific and reliable data.

Testing methodology

Manufacturers are recommended to follow EPA’s established antifungal disinfectant testing protocols to ensure their efficacy. EPA recommends using the latest Product Performance Test Guidelines (OCSPP 810.2200) for hospital disinfectants, and specifically the EPA Microbiology Laboratory Branch (MLB) Standard Operating Procedures (SOPs) MB-35 method for C. auris.

• Quantitative surface test (EPA MLB SOP MB-35): EPA MLB SOP MB-35 provides a standardized method to assess the product’s performance by evaluating antimicrobial efficacy of the product against C. auris on hard, non-porous surfaces.
• Neutralizer validation (MB-37): The latest version of EPA MLB SOP MB-37 can be used to verify the effectiveness of neutralizing agent in stopping the product’s activity at the end of the contact time.
  

EPA also states that in any case, if a test method requires modifications to suit the product needs, manufacturers must ensure that those changes are pre-approved by the agency before conducting the test.  

Additionally, manufacturers can also partner with third-party testing laboratories like MIS, to ensure that their products meet the requirements set by EPA, ultimately reducing the burden of navigating the complexities of Candida auris testing for disinfectants.

Products that must be tested

An EPA-approved product is allowed to make C. auris claims on hospital-based disinfectants, provided the claim is supported by acceptable efficacy data.  Eligible product types include:

• Liquids and water-soluble powders: Standard ready-to-use (RTU) or dilutable liquids and soluble powders. Pump or trigger spray liquids are tested as liquids, using the lowest usable concentration (LCL).
• Aerosols/mists: Products like aerosols, gels, or foams require prior consultation with EPA to design an appropriate test consistent with their use pattern.
• Towelettes (wipes): Wipe products are tested by expressing the liquid from a wipe onto a surface. Data must show how much liquid is deposited on a surface per label instructions.
  

In all cases, antifungal disinfectant testing must mirror the product’s intended use (e.g., dilution, application method) and meet hospital disinfectant standards for formulation and contact time.

Testing criteria

EPA specifies rigorous testing criteria for C. auris tests. Key points include:

• Test organism: A drug-resistant C. auris isolate must be used, specifically AR Bank #0385, as the standard test strain. The cultures can be grown and maintained by following the MLB SOP MB-35 test method.
• Test replicates: Two separate production batches of the product (one batch per day) must be tested at the lowest certified concentration. For each batch, 5 treated carriers and 3 untreated control carriers must be evaluated.
• Neutralizer check: The effectiveness of the neutralizer must be confirmed using EPA SOP MB-37.
• Contact time:  The total contact time between disinfectant and organism must not exceed more than 10 minutes.
• Dilution/preparation: Ready-to-use products can be tested as it is. Dilutable products must be diluted using a recommended diluent (as mentioned on the product label claim).
• Soil load: EPA’s standard three-part organic soil load must be included in the inoculum (e.g., blood, protein, mucin).
• Control counts: Each control carrier must have 1×105 to 1×106 CFU of C. auris before treatment.
• Success criterion: Each test must achieve at least a 5 log10 reduction in viable C. auris (99.999% kill) in each replicate.
  

Any deviations from these procedures must be documented and approved by EPA beforehand. Together, these criteria ensure that only highly effective formulations earn C. auris claims.

Data submission requirements

GLP compliance: 

• All efficacy studies must be conducted under Good Laboratory Practice (GLP) regulations and reported fully to EPA. 
• All antifungal disinfectant testing lab studies supporting registration must adhere to 40 CFR Part 160 (GLP).

Documentation: 

• Manufacturers should submit complete antifungal disinfectant testing reports following EPA’s data guidelines (OCSPP 810.2000)
• Antifungal disinfectant testing reports must describe test procedures, calculations, and results for each carrier. 
• Include control counts, treated counts, and log reductions. Raw data (e.g. actual colony counts) should be provided in appendices.
  

Protocol consistency:

• The test report should reference the specific SOPs used (MB-35 and MB-37) and any EPA-approved modifications.
  

Submitting accurate, GLP-compliant data ensures that EPA can properly review product performance. Well-documented results speed the approval of new claims.

Labeling criteria and claims

If data support a C. auris claim, product labels must use EPA-approved language. According to EPA guidance, acceptable claims include:

• “Kills and/or inactivates C. auris on hard, non-porous surfaces”
• “Kills a minimum of 99.999% of drug-resistant C. auris on hard, non-porous surfaces”.
  

EPA further requires products bearing these claims to include special cleaning instructions. These include:

• Directions to thoroughly remove visible soil and waste (especially feces) before disinfection. 
• Labels should instruct users to wear protective gear (gloves, gowns, masks or eye coverings) during cleaning. 

Including this pre-cleaning and PPE instructions helps ensure that the disinfectant can work effectively and safely against C. auris. It also aligns with EPA’s commitment to overall infection control.

The emergence of drug-resistant Candida auris brings to light the urgent need for effective disinfection protocols in healthcare settings. By strictly following EPA’s guidelines, manufacturers can ensure their products are both effective and compliant.

At MIS, we provide comprehensive antifungal disinfectant testing services to evaluate the effectiveness of your disinfectant products against C.auris. Contact us today to learn more about our testing services.

Reference: https://www.epa.gov/pesticide-registration/guidance-efficacy-evaluation-products-claims-against-drug-resistant-candida#:~:text=EPA%20recommends%20that%20in%20order,Performance%20Test%20Guidelines%2C%20OCSPP%20810.2200.