Demonstration of Mycoplasma gallisepticum in tracheas of healthy carrier chickens by fluorescent-antibody procedure and the significance of certain serologic tests in estimating antibody response.

Chickens naturally infected with Mycoplasma gallisepticum (MG) were cultured by tracheal swab. Although the chickens showed no signs of disease, they remained MG carriers many months after the acute phase of infection. When MG was isolated from tracheas, the agent was demonstrated also in smear preparations from tracheal mucus by the indirect fluorescent-antibody procedure. Humoral immune response to MG was low, as detected by rapid serum-plate-agglutination, micro-tube-agglutination, hemagglutination-inhibition, and agar-gel-precipitation tests. Antigens prepared from three different MG strains gave variable results on the same serum samples. Homologous or heterologous sera obtained from the tested chickens did not inhibit the growth of MG previously isolated from the tracheas.