Biological enrichment of Mycoplasma agents by cocultivation with permissive cell cultures

In this study, we describe our results on the evaluation of the ability of different permissive mammalian cell lines to support the biological enrichment of mycoplasma species known to be bacterial contaminants of cell substrates. The study showed that this approach is able to significantly improve the efficiency of mycoplasma detection based on nucleic acid testing or biochemical technologies (e.g., MycoAlert mycoplasma detection). Of 10 different cell lines (Vero, MDBK, HEK-293, Hep-G2, CV-1, EBTr, WI-38, R9ab, MDCK, and High Five) used in the study, only MDCK cell culture was found to support the efficient growth of all the tested mycoplasmas (Mycoplasma arginini, M. bovis, M. fermentans, M. gallinaceum, M. gallisepticum, M. synoviae, M. hominis, M. hyorhinis, M. orale, M. salivarium, and Acholeplasma laidlawii) known to be most frequently associated with contamination of cell substrates and cell lines in research laboratories or manufacturing facilities. The infection of MDCK cells with serial dilutions of each mycoplasma species demonstrated that these common cell line contaminants can be detected reliably after 7-day enrichment in MDCK cell culture at contamination levels of 0.05 to 0.25 CFU/ml. The High Five insect cell line was also found to be able to support the efficient growth of most mycoplasma species tested, except for M. hyorhinis strain DBS1050. However, mycoplasma growth in insect cell culture was demonstrated to be temperature dependent, and the most efficient growth was observed when the incubation temperature was increased from 28 degrees C to between 35 and 37 degrees C. We believe that this type of mycoplasma enrichment is one of the most promising approaches for improving the purity and safety testing of cell substrates and other cell-derived biologics and pharmaceuticals.