Observation of the Growth Trends of Mycoplasma bovis with Four Different Antigen Quantitation Methods

To explore the antigen harvest time of Mycoplasma bovis (M.bovis) and the antigen quantitation alternative method,M.bovis 08M strain was inoculated in the Thiaucourt's medium.Four growth curve plottings were made by measuring color change units (CCU),colony forming units (CFU),protein concentration and nucleic acid levels.Both the results of CCU and CFU counts showed that the growth of M.bovis was divided into four phases,the logarithmic phase appeared after being cultrured 10 h,the stationary phase appeared at 30 h with the highest number of viable cells up to 1.0×10⁸ CCU/mL and 7.7×10⁷ CFU/mL,and the decline phase started at 75 h.The protein concentration of M.bovis increased rapidly from 15 to 35 h,reached 72.06 μg/mL at 35 h,then maintained at 58.38 to 70.65 μg/mL.The nucleic acid levels of M.bovis increased rapidly from 15 h,and the cycle threshold (Ct) values were maintained between 15.32 to 17.84 after 25 h.These results indicated that there was a good correlation between the protein concentration and viable count of M.bovis at the early stationary phase,which was the best time period to harvest antigen.The protein concentration determination could be an alternative method to quantify antigen contents of M.bovis when preparing inactivated M.bovis vaccine.