Detection of mycoplasma contamination through modulation (stimulation or inhibition) of thymidine incorporation by unstimulated mouse spleen cells.

In the present report we describe a rapid and sensitive assay for mycoplasma detection in cell cultures. The assay is based on the ability of contaminated culture supernatants to modulate [3H]TdR incorporation by unstimulated mouse splenocytes. Several mycoplasma species (Mycoplasma orale, culturable and non-culturable strains of Mycoplasma hyorhinis) inhibited [3H]TdR incorporation and permitted the detection of some contaminated cell cultures that would otherwise have escaped detection in assays measuring [3H]TdR incorporation by mitogen-stimulated splenocytes. On the other hand, several other mycoplasma species (Mycoplasma arginini, Mycoplasma hominis) strongly enhanced [3H]TdR incorporation by unstimulated splenocytes. This enhancement was optimally detectable on day 2 after initiation of the cultures. The sensitivity of the assay was determined for a mycoplasma species (culturable M. hyorhinis) that inhibited as well as for one (M. arginini) that enhanced [3H]TdR incorporation. In both cases, the sensitivity was such that 1-3 x 10(2) mycoplasma colony-forming units (CFU) could be detected.