[Experiences with the demonstration of Mycoplasma in cell cultures].

Over an eight years period about 6200 cell cultures, sera, cell culture media and supernatants were routinely monitored for contamination with mycoplasmas, bacteria and fungi. Mycoplasmas were detected in 24.0% of 4443 samples which were checked for possible contamination. In 1742 samples from a laboratory, known to have only mycoplasma free cultures, 2 were positive, both samples having an external origin. The value of routine monitoring to prevent the introduction of mycoplasma was confirmed. Culture and direct fluorescent assay using the fluorochrome bisbenzimide (Hoechst 33258) yielded comparable results. The applicability and significance of both methods is discussed. In spite of a few disadvantages the culture method is considered to be superior to the fluorescence assay, but both methods should be employed in order to obtain sufficiently reliable results. The importance of appropriate methods for the detection of mycoplasmas is stressed because of their potential influence on experimental results. The probable sources of cell culture contamination are also discussed.