Figure 1.
Quantitative real-time polymerase chain reaction (RT-PCR) standardization for enteropathogenic Escherichia coli (EPEC). A, RT-PCR results from representative experiments using DNA from a pure culture of EPEC E2348/69. Fluorescence from the PCR products is plotted against the corresponding number of copies of intimin (eaeA) gene, corresponding to 101 to 106 bacilli, to obtain the threshold cycle (CT). B, Standard curve for the RT-PCR analysis was done from the same stock of DNA diluted 10-fold. We plotted CT against the log of the number of eaeA copies; the reaction efficiency was >97.3%. C, The melting temperature for the eaeA gene was 83.8 ± 0.23°C; curves are superimposed for the different DNA concentrations used in the analysis. D, Agarose gel (2%): (1–8) PCR products (248 pb) corresponding to the 10-fold dilutions (108 to 101 bacilli); C, No template control; (M) 100-bp molecular weight ladder.