24 Apr 17 Rapid pathogen detection methods — what to consider
With over 40 different assays on the market it is increasingly more difficult for companies to choose a new rapid method and to decide to invest in it. This article discusses the options… [there is some focus on new US regulations the article has plenty of global relevance. Ed]
Why rapid methods?
Rapid methods of pathogen testing have been gaining acceptance in the food industry. Recent advances in technology result in faster detection and identification of pathogens, more convenient, more sensitive, more reproducible, and more specific than conventional methods.
The main reasons for their adaptation are because faster results mean:
- Faster intervention and corrective actions
- Fewer lost lots or reduced amount of product in a contamination event
- Faster reaction to a problem
- Improved throughput and reduced warehouse space
- Decreased manufacturing cycle through faster release of inventory
- Ability to link strains of pathogens to a specific case
- Accelerates root cause analysis
- Rapid pathogen testing can be useful in preventing an outbreak of illness
For ready-to-eat products, the new FSMA [the US’s Food Safety Modernisation Act] proposal requires environmental pathogens to be controlled. As a result, environmental pathogen testing is required in some segments of the industry.
In most cases, the cost of assay materials increases with new methods. However, the operational and financial benefits far outweigh the expense.
It is important to remember, in most foods, rapid methods still lack sufficient sensitivity and specificity for direct testing of the food. Therefore, the foods still need to be enriched in a culture media before the rapid method analysis.
New methods include antibody-based assays, genetic amplification methods, and newer sensor development methods.
Growth-based methods include unique-enrichment methods, chromogenic plates, and film-based methods.
Immunological-based methods include enzyme-linked immunosorbent assay (ELISA) and lateral-flow immunoassay. Also included are immune separation methods, such as immunomagnetic separation (IMS).
Molecular detection methods (nucleic acid-based methods) include simple polymerase chain reaction (PCR), multiplex PCR, real-time PCR (qPCR), nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP) and oligonucleotide DNA microarray.
Biosensor devices are analytical devices consisting of two main elements: a bioreceptor and a transducer. The bioreceptor is responsible for recognizing the target analyte and can either be a biological material (enzymes, antibodies, nucleic acids and cell receptors), or biologically-derived material, or Biomimic: imprinted polymers and synthetic catalysts.
The transducer converts the biological interactions into a measurable electrical signal. It can be optical, electrochemical, mass-based, thermometric, micromechanical, or magnetic.
Whole Genome Sequencing (WGS) has been adopted by regulatory agencies, and is quickly becoming the preferred method for organism identification and comparison.
The FDA has created a whole-genome sequencing network. The GenomeTrakr network is leading investigations of outbreaks of foodborne illnesses and compliance actions. Sequencing provides a much faster response time and means the outbreaks of foodborne illness decrease, as does the number of cases in each outbreak. Some in the food industry have started to use this technology.
Criteria for selecting new methods
Below are a few criteria to consider when investing in new methods of pathogen detection.
Accuracy of results — the degree of accuracy and specificity, ease-of-use, low false positive and negative rate.
Timeliness and automation — the advantages of fast results are listed above. However, the results must be actionable and compatible with the laboratory day. Automation allows the transfer of data to where it is needed.
Platform depth — the range of raw materials, in process, and finished products that can be analyzed, as well as the breadth of assays that can be performed on the platform. The full economic benefits of the new method can only be realized if the vast majority of the company products can be analyzed with it.
System capacity — how many samples can be processed by the system on a daily basis, what is its ease of use, and the training level of the system operators?
The system capacity needs to fit ones requirement for testing and he system must be able to process all the required samples. The labor involved in sample preparation, sample monitoring, and results analysis, as well as the system ability to minimize operator errors must all be taken into consideration.
System support — the commitment of the systems vendor to support the system and provide timely answers to questions is another consideration…..