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Laundry Additives - Residual Self-Sanitization

DIS/TSS-14 July 29, 1981
Efficacy Data Requirements
Laundry Additives – Residual Self-Sanitization

  1. Laundry operations.
  2. A clear distinction should be made on the label between products recommended for household and coin-operated laundering and products represented as commercial-industrial-institutional laundry additives. The water to fabric ratio in home or coin-operated machines is about 10:1 (w/w), whereas in industrial laundering operations the ratio is about 5:1. The effectiveness of products may be significantly altered by these differences; thus, demonstrated efficacy in one system may not be extrapolated to the other. In addition, directions for use of household laundering products may require different dosages for front-loading automatics (e.g., 8-10 gallon water capacity) and top-loading automatics and wringer-type washers (e.g., 12-15 gallon water capacity). Product dosages, in this instance, should be specified in household measurements. Dosage instructions for industrial laundering may be based on pounds of dry fabric.

    The directions for use of laundry additives should specify the machine cycle in which the product is to be added, water level, temperature range, and treatment time. Compatibility of the treatment with other common additives (e.g., soaps, detergents, bleach, starch, bluing, sours, fabric softeners) should be determined in testing an addressed in labeling, when applicable.

  3. Test standard.
  4. A suggested protocol published by Petrocci and Clarke (J. AOAC 52:836-842) is acceptable for treating the fabric. The basic elements outlined in the protocol of the "Quantitative Procedure" of the American Association of Textile Chemists and Colorists (AATCC) Test Method 100-1974 employing Staphylococcus aureus (ATCC 6538) and Klebsiella pneumoniae (ATCC 4352) are acceptable for evaluating the residual antimicrobial activity. However, 3 samples, representing 3 different product batches must be tested, and the following modifications to the method must be incorporated:

    1. Use a sufficient number of swatches placed exactly on top of each other so that they completely absorb 1 ml of inoculum which is prepared to contain at least 107 microorganisms/ml.

    2. The number of swatches used per jar must be reported.

    3. Incubation must be at 20-21 C (68-70 F).

    4. Quantitative bacteriological assays should be performed at the following time intervals: 0, 30 min., 1-hr, 3-hr, 6-hr, and 24-hr. Consideration could be given to fewer or different time intervals, depending on the label claims, on a case-by-case basis.

  5. Performance standard.
  6. For residual self-sanitizing claims against pathogenic microorganisms, the reduction of each test microorganism must be at least 99.9% over the "0-time" control and the parallel untreated inoculated control.

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