The technology does, however, have its drawbacks. Besides the cost implications, the major issue is the effect of the sample matrices. Many sample matrices, such as water or raw meat, contain interfering inhibitory substances that can reduce or completely prevent the amplification process. It is possible to reduce the effect of such compounds by undergoing a secondary enrichment to dilute out the problem; however this makes the methods somewhat less rapid.
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Other technologies exist, such as enzyme-linked immunosorbent assay, or ELISA, and other immunological methods. These methods rely on specific antibodies that capture the target organism, which, in combination with further enzyme chemistry, yields a detectable signal. For this technology to perform, the antibodies utilized must be able to capture all species of interest, which can have highly variable immunological statuses, meaning the antibodies will have variable performance. The detection limit is also lower than that of PCR, but the technology is often cheaper.
Another technology that is gaining greater approval in the food and water testing industry is matrix-assisted laser desorption ionization time-of-flight, or MALDI-TOF. Here laser irradiation is used to vaporize a sample (in the form of biomass from an agar plate), releasing charged ions, which are attracted to a detector. The speed at which the ions reach the detector yields a pattern specific to a given organism from a database, thereby giving an identification. Though this technology is proving popular, its reproducibility and reliability is only as good as the library database it is linked to, and the results can be affected by the state of the cell prior to analysis.
Finally, the most exciting technologies to emerge in pathogen testing as a whole are single nucleotide polymorphisms (SNP) analysis and whole genome sequencing (WGS). These technologies, whilst not quite ready for widespread microbiological food testing, represent a giant leap forward in modern microbiology and further progress our understanding of Campylobacter and its pathogenesis.
An example of implementation and successful use of WGS is the PHE food pathogen reference laboratory. After several years of development, infrastructure building and protocol validation, PHE successfully implemented WGS of Salmonella spp. sent to the reference laboratory. This replaced the lengthy conformation protocol including serotyping and phage typing. A combination of multilocus sequence typing and SNP analysis provide a powerful tool to correctly identify and characterize food pathogens faster and more in depth than able to do before. As well as allowing faster identification and greater ability to source and deal with outbreaks, this technology gives a better understanding of the organism and its source by assessing similarity between genomes. The greatest disadvantage with the technology is, however, the cost and time required to develop a working system for any given organism.
A drawback of all the rapid methods is that, without effective control measures in place to deal with Campylobacter once detected, they might not be able to be utilized as well as they could be.
Clearly there is a great deal of work and development ahead for dealing with Campylobacter. It is evident from current efforts that there is no single step that will solve the problem. It will mostly like be a collection of efforts from all aspects of the food industry—from production all the way to final product testing—that will prevent the prevalence of Campylobacter in poultry.
Elmerhebi is the technical product specialist at Lab M. Reach him at firstname.lastname@example.org.