Study On Cultural Character, Pathogenicity, Immunogenicity Of Mycoplasma Hyopneumoniae MY-99 Strain

The nutrition request of Mycoplasma hyopneumoniae MY-99 strain was very strict. The growth velocity in fluid medium was direct ratio to inoculation quantity and inverse ratio to cultivation volume.It grew slowly on the solid medium and appeared small colony 20 days after inoculated,the diameter of colony was 0.1mm-0.4 mm.The antiserum could suppress its growth and metabolism,the bacteriostasis diameter was 2.11 mm-2.5mm,the highest suppression price was 1:2⁶.Mycoplasma hyopneumoniae MY-99 strain could grow on the saccus vitellinus of chick embryo,and had lethal to chicken embryo.The density respectively was 1×10⁵CCU/ml,1×10⁷ CCU/ml,1×10⁹CCU/ml,1×10¹¹CCU/ml,the lethality respectively is 0,20%,60%,100%.MY-99 strain had pathogenicity which could be confirmed by following experiments.It could cause typical clinical symptom of swine enzootic pneumonia(SEP) to inoculated pigs,such as asthma,cough,and daily gain decrease.The symptom is gravest after 4 weeks.The pathological section demonstrated that the lung hyperemic and hemorrhage obviously,in the bronchial tube and pulmonary alveolus had a great of lymphocyte infiltration.The infected pigs could detect antibody after 2 weeks,the antibody titer achieved highest value 1:2^5.8 after 4 weeks.The average daily gain of inoculated pigs decreased significantly compared to the control pigs,30.01%decreased during postinoculation days 0-10(P＜0.01),35.39%decreased during postinoculation days 11-20(P＜0.01),and 16.18%decreased during postinoculation days 20-35(P＜0.01).The destroy infectivity antigen of Mycoplasma hyopneumoniae MY-99 strain could induce satisfactory humoral immunity.The level of antibody heightened 7days after initial immunity,slightly descended after 20 days and heightened quickly once again after secondary immunity.The antibody OD value achieved 0.68 at 95 day-age and began to descend after 120 day-age.The antibody level above 0.50 kept for 10 weeks,and the OD value of control group was about 0.33 in all experimental stage.The MY-99 strain show its satisfactory antigenicity. Mycoplasma hyopneumoniae MY-99 strain could induce cell immunity,the Ea-RFC%,Et-RFC%and results of T lymphproliferation response were all higher than control group during 0-28 days(P＜0.01).The Ea-RFC%,Et-RFC%and OD value achieved highest value after 14 days,respectively were 31.25%,60.16%and 0.465.The homeochronous value of control group were 17.26%,51.78%and 0.277 respectively.The MY-99 strain's high cell immunity level kept 4 weeks,indicated that the Mycoplasma hyopneumoniae MY-99 strain could stimulate the competence of cell immunity.