[A new method for the microbiological evaluation of disinfecting laundering procedures for textiles]

A new method is described to evaluate the efficacy of disinfecting laundering processes. Testpieces (contaminated cotton fabric patches) are enclosed between a pair of membrane-filter discs. Being immersed in the wash liquor this test system acts as a perfusion chamber permeable for detergent and disinfectant solution but retaining the testbacteria to the testpieces. Tests performed in a shaking water bath as well as practical laundering processes with detergents showed the following: from contaminated test pieces wrapped in cotton fabric - as commonly used in such experiments - test bacteria can hardly be recovered even after a non-bactericidal washing process. This is a result of mechanical wash-off. In contrary, with the new method reductions of viable counts are mainly due to bactericidal effects as physical removal of testbacteria is prevented by the filter membranes. Thus, disinfecting laundering procedures are readily distinguishable from merely cleaning ones. As additional advantage the filter-method prevents test pieces from being contaminated by other bacteria carried by the wash liquor.