Strategies for the inclusion of an internal amplification control in conventional and real time PCR detection of Campylobacter spp. in chicken fecal samples.

To illustrate important issues in optimization of a PCR assay with an internal control four different primer combinations for conventional PCR, two non-competitive and two competitive set-ups for real time PCR were used for detection of Campylobacter spp. in chicken faecal samples. In the conventional PCR assays the internal control was genomic DNA from Yersinia ruckeri, which is not found in chicken faeces. This internal control was also used in one of the set ups in real time PCR. In the three other set-ups different DNA fragments of 109 bp length prepared from two oligos of each 66 bp by a simple extension reaction was used. All assays were optimized to avoid loss of target sensitivity due to the presence of the internal control by adjusting the amount of internal control primers in the duplex assays and the amount of internal control in all assays. Furthermore, the assays were tested against faecal inhibitors to ensure that the internal control and the target PCR had the same sensitivity towards inhibitors.