Detection of Mycoplasma gallisepticum by direct immunofluorescence using a species-specific monoclonal antibody

A monoclonal antibody against Mycoplasma gallisepticum (MG) (strain S6) was prepared in mice and identified as isotype IgG1 by standard procedures. Although it did react at high titers (1:100,000) in the enzyme-linked immunosorbent assay (the original method for its identification), it failed to react in the agglutination, hemagglutination-inhibition, and growth-inhibition tests. When conjugated to fluorescein isothiocyanate, the monoclonal antibody reacted with the homologous and eight "atypical" strains of MG but not with M. meleagridis or M. synoviae in the direct fluorescent-antibody test. This reagent may be useful for detecting field infections involving atypical strains of MG.