Effects of pleuropneumonia-like organisms on cultured human cells

Abstract

A strain of PPLO isolated from contaminated tissue cultures exhibited the typical characteristics of mycoplasma by agar cultivation and electron microscopy and was sensitive to Aureomycin. Among many types of cultured cells studied, human amnion cells of the FL line showed the most pronounced morphological changes (cytopathic effect) and cell destruction as a result of infection with this strain. The mycoplasma, as observed by the direct microscopic demonstration method in association with FL cells, had an average diameter of 308 mμ. The titers in the tissue culture fluid approximated 10 7 colony-forming units (CFU) per ml. This PPLO strain, and many other strains, propagated to considerable titers (approximately 10 6 CFU/ml) also in two freshly prepared cell-free tissue culture media (slightly better in yeast extract-containing medium, LY medium). In infected FL cell cultures, after an initial period of normal division, the FL cell population decreased due to extensive cell destruction. Subsequently, a population of cells increased at a reduced rate. The latter population, which has been carried up to twelve months in serial transfer in the presence of high PPLO titers, is morphologically different from uninfected FL cells. The deleterious cell effects of this PPLO strain were not diminished by an increase in the l-arginine concentration in the culture medium.