Estimation of the growth of the T 1 strain of Mycoplasma mycoides in tryptose broth by the measurement of lactate dehydrogenase. I. Method.

A highly significant correlation coefficient (r = 0.97, n = 18) was found between the concentration of lactate dehydrogenase measurable after the organisms had been disrupted and the concentration of colony-forming units during the logarithmic phase of growth of a broth culture of the T(1) strain of Mycoplasma mycoides var. mycoides. A concentration of 4.60 x 10(-7) milliunits of lactate dehydrogenase for each colony-forming unit was established. This relationship was used to convert the concentration of lactate dehydrogenase in the culture into an estimate of the concentration of viable mycoplasma. The lactate dehydrogenase was estimated by following the oxidation of reduced nicotinamide adenine dinucleotide, in the presence of pyruvate substrate, at 366 nm in a spectrophotometer. The nicotinamide adenine dinucleotide oxidase system probably contributed a small amount of enzyme activity to the test when lactate dehydrogenase was measured in this way. The method has been described and evaluated for the estimation of titers from 10(7) to 5 x 10(9) colony-forming units per ml.