Clostridioides difficile is an important concern for healthcare laundries because its spores can persist on contaminated textiles and resist many conventional disinfectants. Effective C. diff laundry disinfection depends on both the chemistry used and the conditions the textiles encounter throughout the wash process. Peracetic acid (PAA)-based laundry products provide healthcare laundries with an option for deactivating C. diff as part of a properly controlled wash formula.
While sodium hypochlorite has long been recognized for its sporicidal properties, less information has been available on how C. diff spores respond to the conditions found in a tunnel washer when PAA is used as the bleaching agent. A study funded by the American Reusable Textile Association (ARTA) examined that question. Their work evaluated individual laundry chemistries and then simulated the cumulative conditions that healthcare textiles experience as they pass through a tunnel washer. The actual peer-reviewed, published study can be found here: https://www.sciencedirect.com/science/article/pii/S0196655319304638
PAA-based laundry products vary in strength and formulation, with different concentrations of peracetic acid, hydrogen peroxide, and acetic acid. For example, formulations containing 15% PAA may include 10% or 22% hydrogen peroxide, with corresponding differences in acetic acid content. These variations can influence chemical performance, so healthcare laundry operators should select a formulation suited to their wash conditions and C. diff decontamination requirements.
What Kills C. diff in Laundry?
The testing was conducted in two phases. Phase I evaluated the ability of selected laundry chemistries to reduce viable C. diff spores on inoculated cotton swatches. The test conditions incorporated agitation and temperatures appropriate for the individual chemicals rather than evaluating chemistry under a single set of conditions.
Inoculated swatches were exposed for eight minutes to alkaline detergent, sodium hypochlorite, hydrogen peroxide, or PAA. Following exposure, surviving spores were recovered from both the textile swatches and chemical solutions and enumerated using standard microbiological assay methods. This test served as a control for comparison with Phase II, which tested the cumulative effect of the test chemicals.
Sodium hypochlorite produced greater than a 5-log10 reduction of spores on the swatches and greater than a 3-log10 reduction in the wash solution. A 5-log10 reduction means a 99.999% reduction in the number of live microorganisms, leaving only one survivor out of every 100,000 originally present. This is generally considered the threshold for achieving “sanitization.” PAA tested alone produced only a 0.26-log10 reduction in the wash solution during this phase. Those results confirmed the sporicidal performance of sodium hypochlorite but raised another question about PAA: How would it perform as part of an entire tunnel wash process rather than as an individual chemical exposure?
Testing C. diff Laundry Disinfection in a Tunnel Washer Process
Phase II was developed to more closely represent the conditions encountered in an operating healthcare laundry. C. diff-inoculated swatches were passed through a simulated 24-minute tunnel washer process using five wash liquids.
The sequence moved the swatches through alkaline and detergent modules, PAA bleaching, and a final rinse. Temperature, pH, agitation, chemical exposure, dilution, and successive wash solutions became parts of the overall process rather than evaluating PAA independently. Spore survival was again measured on the textiles and in the wash liquids.
The results differed considerably from the Phase I PAA test. The complete process using PAA at neutral pH achieved greater than a 5-log10 reduction of C. diff spores on the swatches. Cumulative reduction measured in the wash solutions reached greater than 3.08 log10 in the final module.
What the Results Mean for C. diff Laundry
For an existing healthcare laundry, the Phase II results are especially useful because textile decontamination takes place across a wash formula. Chemistry is one part of a process that also includes time, temperature, mechanical action, dilution, rinsing, pH control, and the movement of contaminants away from the textile.
The distinction between destruction and removal also matters. PAA alone showed minimal spore reduction in the Phase I wash solution, yet the complete PAA tunnel process reduced recoverable spores on the textiles by more than 5-log10. The data support evaluating the cumulative wash process when determining how effectively a tunnel formula controls C. diff contamination. They should not be interpreted as evidence that any PAA formula, concentration, or tunnel configuration will produce the same result.
Existing healthcare laundries can use these findings when reviewing chemical concentrations, pH, temperatures, module sequencing, wash time, rinsing, and water exchange. Effective microbial control depends on maintaining the conditions under which the complete process performs as intended.
Improve Your C. diff Laundry Disinfection Process
The study confirmed the sporicidal activity of sodium hypochlorite and demonstrated that a simulated tunnel washer process using PAA at neutral pH achieved greater than a 5-log10 reduction of C. diff spores on contaminated textiles through the cumulative impact of wash chemicals, temperature, and mechanical action. For healthcare laundries, the findings reinforce the need to evaluate the complete wash formula, including chemistry, operating conditions, dilution, and removal, when assessing C. diff control.
Gurtler Industries has a variety of PAA-based laundry products that may be of interest to laundries considering improvements to their laundry disinfection process. Contact Gurtler Industries, Inc. to review your healthcare laundry disinfection process and determine how your wash chemistry and tunnel operating conditions can be optimized for effective microbial control.
