Characterization of toxic extracts of in vitro cultured human plaque

Studies were conducted to characterize the water soluble cytotoxic substances elaborated in vitro by cultured human plaque. A complex bacterial plaque, derived from scrapings of whole human plaque, was cultured in a programmable culture apparatus. Exposure of tissue culture media to the cultured plaque rendered it toxic to mouse L929 fibroblasts. This toxic activity was not alleviated by addition of exogenous tissue culture nutrients, fractionated with a molecular weight of less than 1000 daltons and was heat stable. Water extracts of the cultured plaque contained similar low molecular weight toxic factors. In contrast, extracts prepared from vigorously disrupted plaque contained high molecular weight toxins which were in part sensitive to heat inactivation. These findings demonstrate that a heterogenous cultured plaque does elaborate water soluble toxins and that such factors represent only a fraction of the total complement of water soluble toxins contained within that plaque.