Construction of the standard curves for <i>bla</i> and <i>dxs</i>.

<p>(A) The standard curves were calculated with serial 10-fold dilutions of pGEM-dxs, ranging from 1 × 10⁵ to 1 × 10⁹ copies μl^-1. Each standard dilution was amplified by qPCR using <i>bla</i> and <i>dxs</i> primer sets (<i>n</i> = 2). For each gene, the determined C_T values were plotted against the logarithm of their known initial copy number. A standard curve was generated by linear regression through these points. (B) Validation of the ΔΔC_T calculation. The ΔC_T deviation of <i>bla</i> vs. <i>dxs</i> was calculated for each dilution and plotted (<i>n</i> = 2). Average ΔC_T = average ± SD (<i>n</i> = 10).