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.

Improved method for tuberculocidal and mycobactericidal activity testing of disinfectants based on the European Standard EN 14348.

Safe measurements to prevent the transmission of (multidrug-resistant) mycobacteria such as disinfection are essential in healthcare settings. In Europe chemical disinfectants are tested for their tuberculocidal and mycobactericidal efficacy by the internationally accepted test procedure described in EN 14348. However, especially for amine-based disinfectants, invalid results may occur by this procedure due to insufficient neutralization. In this multi-laboratory study the procedure described in EN 14348 was optimized by a combination of chemical neutralization and membrane filtration in order to obtain a valid and secure method especially for amine-based disinfectants.