from L. Jesús Garcia-Gil writing in Real-Time PCR in Food Science: Current Technology and Applications:
Campylobacter is a microaerophilic, spiral shaped, Gram-negative bacterium comprising 16 species. Although many of these species are thermotolerant, i.e. able to grow at 42 degrees C, C. jejuni, C. coli, C lari, and C. upsaliensis are the most prevalent foodborne pathogens. The need for a fast detection of these bacteria in foodstuff has fostered the development of rapid method, most of them based on PCR techniques. Nevertheless, the use of the appropriate targets has limited the development of reliable methods. This difficulty arises, in part, from the fact that target genes used commonly, either virulence genes or ribosomal, contain high variability, even among strains. This has serious implications, for instance, as false negative results. As a consequence, the number of available PCR protocols to detect thermotolerant Campylobacters is very limited. The use of strongly conserved, housekeeping genes as PCR targets has resulted in a good approach to the ideal real-time PCR based method. The difficulty in such a task is actually reflected in the scarce officially certified tools commercially available.
Further reading: Real-Time PCR in Food Science: Current Technology and Applications