General principles of laboratory diagnosis of mycoplasma infections

Laboratory diagnosis includes 1) methods for direct microscopic demonstration of mycoplasma cells and antigens in animal and plant tissues or excreta, and cell cultures, 2) methods for isolation and growth of mycoplasmas from the said sources, and 3) techniques for identification and classification of mycoplasma isolates by a) determination of biochemical characteristics, and b) serological tests. A great many techniques are available for each of these purposes. Some of them have been used routinely for several years. Other methods that appeared promising when they were first introduced have never obtained general usage or they have more limited applications. Pertinent techniques will be reviewed and described. For demonstration of mycoplasmas in tissues, particular emphasis will be placed on immunofluorescence and immunoperoxidase tests. Attempts at isolation and cultivation of mycoplasmas should take into consideration the source, collection and transport of materials, elimination of growth-inhibiting factors in animals and plant tissues, special growth requirements of mycoplasmas, and the importance of cloning of cultures as a preliminary to further characterization. Although a number of biochemical tests are available for general characterization of mycoplasma isolates, precise identification of the species can usually be made only by serological techniques. For that purpose, growth inhibition, immunofluorescence, and (in the case of spiroplasmas) the deformation test combine the advantages of being highly specific and relatively easy to perform, and hence have obtained most widespread usage.