Use of the pour plate technique in tuberculocidal efficacy testing according to EN 14348 - a comparative study.

Effective disinfection strategies are essential to prevent the spread of Mycobacterium tuberculosis. Tuberculocidal efficacy of disinfectants can be demonstrated by testing disinfectants in in-vitro tests, such as the well-established quantitative suspension test EN 14348 using Mycobacterium terrae as a surrogate organism in European disinfectant testing. In other European standard tests, such as EN 13727 and EN 13624, use of the pour plate technique is well established; however, in EN 14348, the spread plate technique alone is considered. Comparative experiments according to EN 14348 with M. terrae were conducted using a peracetic-acid-based disinfectant. Either the pour plate technique or the spread plate technique was used for cultivation. Differences in colony size and morphology were observed when comparing the growth of M. terrae on pour plates compared with spread plates. However, no significant differences in biocidal efficacy data were obtained when applying either spread plates or pour plates in the quantitative suspension test described in EN 14348 under both clean and dirty conditions.

Comparison of a rapid detection fluorescence-based assay targeting tuberculocidal efficacy with EN 14348 and EN 14563.

BACKGROUND: A rapid test system using fluorescent Mycobacterium terrae to evaluate the tuberculocidal efficacy of disinfectants has recently been published. Results were obtained in a significantly shorter time than was previously possible. AIM: To compare the European Standard test system with the fluorescence assay and to validate the rapid test system, including particularly the quantitative suspension test. METHODS: Quantitative suspension tests and quantitative carrier tests were carried out according to EN 14348 and EN 14563, respectively. Quantitative carrier tests and subsequent green fluorescent protein (GFP)-based determination of germicidal efficacy were carried out as described previously. A peracetic acid-based formulation was used as a test germicide. FINDINGS: Testing of the germicide in the quantitative suspension test EN 14348 and in the quantitative carrier test EN 14563 revealed tuberculocidal efficacy at a concentration of 1% after 15 min contact time. Accordingly, data obtained from the fluorescence assay demonstrated that a germicide concentration of 1% was effective after 15 min, indicating no live mycobacteria following this treatment. Thus, identical in-use parameters for tuberculocidal efficacy were obtained either by applying the quantitative suspension and quantitative carrier tests EN 14348 and EN 14563 or by using the GFP-based rapid test system. CONCLUSION: The GFP-based rapid test system compares well with the established European Standard test procedure including both phase 2, step 1 and phase 2, step 2 tests and provides a rapid and sensitive tool for testing germicides for relevant in-use concentrations and contact times.