The sensitivity for each PCR assay was determined using the standard curves prepared with purified genomic DNA of cultures of C. jejuni NCTC 11168 and C. coli CIP 70.81, ranging from 101 to 108 genome copies per 5 μL of template (PCR reaction). In order to mimic realistic conditions and to determine the detection limits of C. coli and C. jejuni real-time PCR assays for field samples, different standard curves were prepared to quantify C. coli or C. jejuni in faecal, feed, and environmental samples. Campylobacter-negative faecal samples

were spiked with 10-fold dilutions series of viable suspensions of each reference strain (C. EPZ015938 order jejuni NCTC 11168 and C. coli CIP 70.81), ranging from 101 to 108 Colony Forming Units per gram of faeces (CFU/g). Standard curves for environmental and feed samples were constructed in a similar way. DNA was extracted from each of the spiked samples and tested in real-time PCR, where the standard curves were created automatically by the ABI PRISM® 7300 Sequence Detection System Software by plotting the Ct values against each standard dilution of known concentration. Intra- and inter- assay variabilities The assay variability was established by repeatedly testing samples containing several concentrations of C. coli and C. jejuni spanning the whole range covered

by each real-time PCR in different assays (10 consecutive runs) and within an assay (10 duplicates in the same assay), click here in order to calculate the inter- and intra-assay coefficients of variation (CV) for the Ct values experimentally determined, as previously described [63]. To assess the intra-assay variation,

each dilution of purified genomic DNA of cultures from C. jejuni NCTC 11168 and C. coli CIP 70.81 from approximately 101 to 108 CFU were measured 10 times each within one PCR run. The inter-assay variation was evaluated with the same different dilutions of purified genomic DNA in 10 independent PCR experiments on different days (10 different runs). For each PCR run, each dilution point was tested in duplicate and the mean standard curve was used for quantity estimation. To assess the method with field samples, the values for the intra- and inter-assay variations of the real-time PCR assays were Resminostat obtained with the DNA extracted from the Campylobacter-negative spiked samples. To assess the intra-assay variation, DNA extracted from the Campylobacter-negative faecal samples spiked with 10-fold dilutions of the Campylobacter suspensions, ranging from 2.5 × 107 to 2.5 × 102 CFU of C. coli/g of faeces and from 2.0 × 107 to 2.0 × 102 CFU of C. jejuni/g of faeces, were measured 10 times each within one real-time PCR run. The inter-assay variation was evaluated with different dilutions of DNA extracted each time with a specific extraction from the Campylobacter-negative spiked faecal samples in 10 independent real-time PCR experiments on different days. For each real-time PCR run (C.