Study on the Correlation between Spectrophotometric Method and Live Bacterial Count Method for Determining the Concentration of Bacterium Solution of Avibacterium paragallinarum
In order to establish a rapid method for determining the concentration of Avibacterium paragallinarum in liquid form,representative strains of Avibacterium paragallinarum serotypes A,B and C were selected in this study(strains CVCC254,CVCC257 and CVCC256),The viable bacterial count value was determined at the same time.Regression analysis of the two sets of data,obtain the regression equation and the standard curve,analyse the coefficient of determination(R2)of the regression equation and the dispersion of the point line of the standard curve,and determine the optimal measurement wavelength.Then the bacterial solutions at different incubation time points(10 h,12 h,14 h,16 h,18 h,20 h)were selected,and their OD values were measured at the optimum wavelength and substituted into the regression equation to obtain the number of viable bacteria,the viable bacteria counting method was also used to obtain the viable bacteria count values,and the two sets of data were statistically analysed using SPSS 17.0 software to further validate the correlation between the spectrophotometric method and the viable bacteria counting method to determine the concentration of bacterial fluids.The results showed that there was an optimal linear relationship between the OD values and the viable bacterial count values of the three strains of bacterial fluids measured at 600 nm,and it was determined that the optimal wavelength for the determination of their bacterial concentration was 600 nm for all of them.The regression equations were y = 14.302x-0.1441(R2 =0.9962),y =14.464x-0.2746(R2 =0.995),and y =14.681x-0.01326(R2 = 0.9989),respectively,with y as the viable bacteria count value(×108 CFU/mL)and x is the OD600 value.The values of viable bacteria obtained by substituting the OD values of the three strains cultured to the pre-decline stage measured at 600 nm into the regression equation were not significantly different from their viable count values(P>0.05).The results of the study showed that the spectrophotometric method of pre-decline Avibacterium paragallinarum bacterial fluids correlated well with the viable count method.Therefore,the spectrophotometric method can be used for the rapid determination of the concentration of Avibacterium paragallinarum bacterial fluids before the decline period.
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