81 suspension, ranging 2.5 × 102 to 2.5 × 107 CFU/g of faeces and (b) C. jejuni NCTC 11168 suspension, ranging 2.0 × 102 to 2.0 × 107 CFU/g of faeces, each dot representing the result of duplicate amplification of each dilution. The coefficients of determination R2 and the slopes of the regression curve are indicated. The standard curve is obtained by correlation of the threshold cycle values (Ct) and log10 input CFU/g of faeces (Log CO) from the amplification plot. To obtain values for the intra- and inter-assay variation of each real-time PCR assay with field samples, DNA extracted from the Campylobacter-negative spiked faecal samples was subjected to each real-time PCR in ten duplicates, find more with

10 different mixes performed on different runs. The results

are reported in Table 2. The CV of the Ct values for the ten different intra-assay experiments ranged from 1.15 to 4.40% for C. coli real-time PCR and from 0.91 to 2.53% for C. jejuni real-time PCR. selleckchem The standard curves were y = -3.33x + 45.82 with R2 = 0.98 for C. coli and y = -3.24x + 46.00 with R2 = 0.98 for C. jejuni. The CV of the Ct values for the ten different inter-assay experiments, including the DNA extraction procedure, ranged from 0.57 to 2.58% and from 0.70 to 2.10% respectively for C. coli and C. jejuni real-time PCR assays. The mean standard curves were y = -3.36x + 43.70 and y = -3.25x + 46.20 respectively. Analysis of faecal samples of experimentally infected pigs The numbers of positive

and negative samples for experimentally infected pigs determined by either real-time PCR or bacteriological method are summarized in Table 3. There was an excellent correlation at the qualitative level with both techniques with a kappa of 0.94 and 0.89 respectively for C. coli and C. jejuni real-time PCR assays. Indeed, for C. jejuni experimentally infected pigs, only two culture-positive samples were negative by real-time PCR, and one culture-negative sample stiripentol was positive by real-time PCR (specificity of 96.2%). In addition, for pigs experimentally infected with C. coli, only one culture-negative sample was positive by real-time PCR and inversely (specificity of 96.2%). Table 3 Comparison of real-time PCR and microaerobic culture in faecal samples of experimentally infected pigs for the detection of (3.1) Campylobacter coli and (3.2) Campylobacter jejuni       Microaerobic culture         + – Total     + 40 1 41 3.1 Campylobacter coli detection Real-time PCR – 1 25 26     Total 41 26 67     + 24 1 25 3.2 Campylobacter jejuni detection Real-time PCR – 2 25 27     Total 26 26 52 3.1 Sensitivity Se = 97.6%, Specificity Sp = 96.2%, Kappa K = 0.94 3.2 Sensitivity Se = 92.3%, Specificity Sp = 96.2%, Kappa K = 0.89 The estimate of Campylobacter CFU/g of faeces by both C. coli and C. jejuni real-time PCR assays was compared to the bacteriological enumeration method (Figure 4).