This approach could potentially shave days off currently used food-testing protocols and help minimize health risks, and economic losses, in the food industry. In addition to microbial food contaminations, the RAPID capture method can also be applied to the analysis of environmental samples, including water and soil samples, to improve environmental monitoring and microbial research at sites of interest.
Credit: Wyss Institute at Harvard University Wyss Institute researchers have leveraged their pathogen capture platform — originally developed for sepsis diagnosis and therapy — to devise a technology that is able to rapidly isolate contaminants from different food products in sufficient amounts to allow immediate testing for specific microorganisms without the need for further enrichment.
Such instruments measure changes in the growth medium at regular intervals for example, six minutes for the Bactometer and record the time required for sharp and significant changes in the impedance as the detection time DT or impedance detection time IDT. DTs and IDTs are inversely proportional to the initial microbial load in the sample. The IDT and slope of the impedance curves provide valuable information about the initial levels, generation times and growth densities in the sample.
These instruments can be used to detect poor quality or substandard samples in less than eight hours, offer low cost per test, and offer high capacity in terms of simultaneous tests up to in the case of the RABIT.
The computerized data handling, storage and retrieval is an attractive feature offered by these systems.
Numerous applications of the impedance and conductance methods in dairy microbiology have been recently developed. The Bactometer has been used for detection of abnormal milk, estimation of bacteria in raw and pasteurized milk and dairy products, detection of antibiotics, measurement of starter culture acitivity and determination of bacteriophage, and monitoring milk quality and predicting the shelf life of pasteurized milk.
The Malthus system has been used for detection of post-pasteurization contamination of pasteurized milk, estimation of lactic acid bacteria in fermented milks, detection of psychrotrophic bacteria in raw milk, and detection of microorganisms in powdered milks. Recently, conductance methods for detecting Salmonella and for the enumeration of Enterobacteriaceae in milk have been reported. The immunoassay is based on the qualitative or quantitative determination of antigen or antibody present in a sample by specific antigen- antibody reaction, which can be visualized in terms of clumping or agglutination, color or fluorescent development from an enzyme reaction or formation of an immunoband.
The development of monoclonal antibodies directed against specific antigenic fractions of targeted microorganisms or toxins has led to the application of a number of immunological techniques to the industry.
The enzyme immunoassay EIA and the enzyme-linked immunosorbent assay ELISA are the most commonly used techniques for rapid detection of pathogen and toxins. ELISAs have been designed for the detection of specific pathogens, toxins and enterotoxins, antibiotics, drug and pesticide residues, and some are designed to detect specific organisms such as Salmonella Enteritidis or Listeria monocytogenes from food or environmental samples.
There are many types of immunoassay from which to choose, as well. The highly automated and sensitive laboratory bench-top instruments based on immunoassay have increased time to result substantially over the last few years, as well. The use of immunomagnetic beads coated with antibodies specific for target organisms, once considered novel, are also now widely used. A recent spate of food product recalls due to Listeria contamination, particularly L.
The kit was validated to detect Listeria spp. Antibodies are coated onto magnetic beads that are used in the assay to capture the antigen. This system separates the cells from the food debris. The antigen reacts with the alkaline phosphatase conjugated antibody. The substrate is added resulting in a fluorescent signal. Samples are read on an EiaFoss Type instrument in which a program card is inserted to control specific ELISA kit operating parameters such as incubation times and cut-off points.
Q-Laboratories Ltd. The two methods agreed on out of analyses. Also of note are two AOAC International Official Methods previously validated for food testing that were also recently granted method applicability extensions to include Listeria environmental surface testing. The assays, which provide visual indicators within minutes, are the first two rapid tests to have been collaboratively validated and approved for this purpose.
This a pathogen for which many immunoassay-based systems and kits have been developed and successfully used by food manufacturers. The test requires a flail hour enrichment step that ensures that very low levels of sub-lethally injured cells are recovered and detected.
The method has been validated for composite gram ground beef samples to reduce the amount of testing to be performed. The EiaFoss E. The system can run up to 27 samples per run and the test time on the analyzer after enrichment is less than two hours, with a total test time, including enrichment, of 24 hours. The Detex system The MC system is designed to simultaneously assay up to 27 samples at a time, and allows the analyst to test for multiple pathogens at the same time with results in approximately two hours.
The rapidity and sensitivity of immunoassay-based test kits and systems have come a long way in the past few years due to developments in immuno-precipitation devices, lateral flow devices and immunomagnetic separation IMS techniques. For example, one can combine the IMS and differential plating media to isolate and detect pathogens such as Listeria monocytogenes, E.
This technique has been established for quite some time, but recently has enjoyed renewed interest by food industry scientists. The PCR method is a highly specific and sensitive method allowing the detection of low numbers of microorganisms. In the past, the general limitations of the technique have included difficulty in obtaining specific DNA primers and production of nonspecific PCR products.
Also, organisms that have been killed during processing were not recognized as dead if their DNA was still present, thus giving false-positive reactions. Automation and improvements in PCR systems have addressed some of these problems and made the technique an extremely attractive option. Validated to detect L. Detection of these DNA fragments provides a highly reliable indicator that L. The BAX system incorporates all necessary reagents, primers, and polymerase into a single tablet that is prepackaged in a PCR tube.
The test is easy to run, requiring only basic microbiology skills, and takes about three hours of processing time after pre-enrichment broth samples are incubated. This study had showed that the detection limit for Escherichia coli O without enrichment was 1. Niu et al. Moreover, Xu et al. Lateral flow immonuassay is also used for detection of other foodborne bacterial pathogens such as Listeria spp.
It can also be used to detect toxins which may cause foodborne diseases such as brevetoxins and staphylococcal enterotoxin B Zhou et al. Commercial immunochromatographic test strips are also available for the detection of foodborne bacterial pathogens. Examples of the application of immunological-based methods for the detection of various foodborne pathogens present in food samples. The summary of advantages and limitations of each rapid detection methods. Conventional methods for the detection of foodborne pathogens which based on culturing the microorganisms are selective, but they can be time-consuming and laborious.
Hence, various rapid detection methods have been developed in order to overcome the limitations of conventional detection methods. Rapid methods are important for the rapid detection of foodborne pathogens in food products to prevent outbreaks of foodborne diseases and the spread of foodborne pathogens. Rapid detection methods are generally more sensitive, specific, time-efficient, labor-saving, and reliable than conventional methods. Nucleic acid-based methods such as PCR, mPCR, qPCR, and DNA microarray have high sensitivity and they are widely used for the detection of foodborne pathogens, but these methods require trained personnel and specialized instruments.
They do not require thermocycling system therefore they are useful especially in low resource settings. Furthermore, numerous biosensors-based methods have recently emerged and employed in the field of foodborne pathogen detection due to their rapidness and cost effectiveness.
Biosensors-based methods are easy to operate and they do not require trained personnel, furthermore the techniques can be used for the detection of foodborne pathogens without sample pre-enrichment. However, improvement in food matrixes detection is still needed for these methods for on-site detection.
Immunological-based methods such as ELISA and lateral flow immunoassay are also used for the detection of foodborne bacterial pathogens and their toxins. Immunological methods work best in the absence of interfering molecules in the samples such as non-targeted cells, DNA or proteins. Combination of several rapid methods for the detection of a particular foodborne pathogen is also possible as the use of only one detection method may not be sufficient to confirm the detected pathogen.
Further studies on the effect of different combinations of rapid methods for foodborne pathogen detection are required in order to develop the most effective and accurate detection method.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. HA to Dr. GBA awarded to Dr. Lee Learn-Han. National Center for Biotechnology Information , U.
Front Microbiol. Published online Jan Author information Article notes Copyright and License information Disclaimer. This article was submitted to Food Microbiology, a section of the journal Frontiers in Microbiology. Received Oct 21; Accepted Dec The use, distribution or reproduction in other forums is permitted, provided the original author s or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice.
No use, distribution or reproduction is permitted which does not comply with these terms. This article has been cited by other articles in PMC. Abstract The incidence of foodborne diseases has increased over the years and resulted in major public health problem globally. Introduction Foodborne diseases have become a major public health problem worldwide due to the significantly increased incidence of foodborne diseases over the last 20 years Oliver et al.
Polymerase chain reaction PCR One of the most commonly used molecular-based method for the detection of foodborne bacterial pathogens is polymerase chain reaction PCR.
Table 1 Examples of the application of nucleic acid-based methods for the detection of various foodborne pathogens present in food samples. Open in a separate window. Oligonucleotide DNA microarray The recent progress in multi-gene detection technology includes the microarray technology Call et al.
Biosensor-based methods Biosensor is an analytical device that consists of two main elements: a bioreceptor and a transducer. The bioreceptor responsible for recognizing the target analyte can either be a: Biological material: enzymes, antibodies, nucleic acids and cell receptors, or Biologically derived material: aptamers and recombinant antibodies, or Biomimic: imprinted polymers and synthetic catalysts.
Table 2 Examples of the application of biosensor-based methods for the detection of various foodborne pathogens present in food samples. Optical biosensors The most commonly used optical biosensor for the detection of foodborne pathogen is surface plasmon resonance SPR biosensor due to their sensitivity.
Electrochemical biosensors Electrochemical biosensors are further classified into several types such as amperometric, impedimetric, potentiometric, and conductometric according to the measurement of changes in current, impedance, voltage and conductance respectively, which caused by antigen-bioreceptor interactions Zhang, Mass-based biosensors Mass-based or mass-sensitive biosensors operate based on the detection of small changes in mass.
Immunological-based methods The detection of foodborne pathogens by immunological-based methods is based on antibody-antigen interactions, whereby a particular antibody will bind to its specific antigen. Table 3 Examples of the application of immunological-based methods for the detection of various foodborne pathogens present in food samples. Table 4 The summary of advantages and limitations of each rapid detection methods. Mandal et al.
Conclusion Conventional methods for the detection of foodborne pathogens which based on culturing the microorganisms are selective, but they can be time-consuming and laborious.
Conflict of interest statement The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. References Adzitey F.
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