pH Responded Colorimetric ELISA for Sensitive Detection of Salmonella Choleraesuis in Milk

Human maybe get poisoning after eating Salmonella choleraesuis-infected food. Thus,developing a new analytical technology for rapid and sensitive detection of Salmonella choleraesuis in food is urgently needed. Hence,a pH responded colorimetric enzyme-linked immunosorbent assay(pH-ELISA)was developed for sensitive detection of Salmonella choleraesuis in milk. In this method,glucose oxidase(GOx)was used to catalyze glucose for the generation of gluconic acid. The color of bromocresol purple(BCP)was changed from purple to bright yellow because the pH of sample solution decreased. Under the optimal conditions,the proposed method achieved two linear independent regression equations. When Salmonella choleraesuis concentration increased from 2.54×10³ to 6.17×10⁵ CFU/mL,the first regression equation was described as y₁=0.1051ln(x)+0.7024(R²=0.7513). With the increase of Salmonella choleraesuis concentration from 6.17×10⁵ to 1.67×10⁷ CFU/mL,the second regression equation was expressed as y₂=1.3216ln(x)-15.797(R²=0.9711). The average recoveries of the proposed method for spiked milk samples at Salmonella choleraesuis concentrations ranging from 2.5×10³~5.6×10⁶ CFU/mL were 72.16%~103.58% with the relative standard deviations ranging from 7.54%~15.30%. In conclusion,the developed colorimetric ELISA is suitable for the rapid and sensitive quantitation of Salmonella choleraesuis in milk.