Biosensor allows rapid testing of L. monocytogenes in food study

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By Jane Byrne, 23-Apr-2009

US and Indian scientists have developed a new biosensor for use in a faster, more sensitive test for detecting the deadliest strain of Listeria food poisoning bacteria, according to an article in the current issue of Analytical Chemistry.

The researchers note that numerous fast, highly effective tests already are available for five of the six known species of Listeria, which use antibodies that signal the presence of the bacteria. However, they claim that no rapid, sensitive tests are available for detecting Listeria monocytogenes.

The foodborne pathogen L. monocytogenes causes human listeriosis affecting pregnant women, newborns, the elderly and immunocompromised individuals, with the microbe causes hundreds of deaths and thousands of hospitalizations each year in the US.

Stubborn pathogen

According to the authors of the study, Listeria can tolerate salt, pH changes, inadequate thermal pasteurisation and refrigerated temperatures, with major sources of listeriosis outbreaks being fully processed ready-to-eat (RTE) foods, which can be contaminated by poor hygienic practices during post-processing handling and packaging.

The scientists explained that their biosensor uses heat shock proteins instead of the antibodies used in other tests, and they said the results of their study showed that their sensor was faster and more sensitive at detecting the bacterium than antibody-based tests, with a microbe capture rate up to 83 per cent higher than antibody-based tests.

The new biosensor will reduce the likelihood of false-positive results for L monocytogenes in food and may lead to improved tests for detecting other types of pathogens, added the researchers.

Inhibition using film

Meanwhile, an extruded composite food packaging film containing pectin, polylactic acids (PLAs) and nisin can inhibit L monocytogenes, according to scientists based at the Agricultural Research Service (ARS) of the US Department of Agriculture.

The scientists said that they chose brain heart infusion (BHI), orange juice and liquid egg white as the foods for the study as they serve as representatives for neutral, high acid and low acid foods respectively.

The film, found the researchers, was effective in reducing L. monocytogenes by 2.1, 4.5 and 3.7 log units mL-1 in the BHI, as well as in the orange juice and liquid egg after 48 hours at 24C.

The ARS scientists concluded that this composite film has great potential to reduce post-process growth of food pathogens, and they added that they will further explore the use of nisin containing films as packaging materials with antimicrobial activity against L. monocytogenes for solid foods such as meat products.

Source: Analytical Chemistry
Title: Targeted Capture of Pathogenic Bacteria using a Mammalian Cell Receptor coupled with Dielectrophoresis on a Biochip
Published online: DOI: 10.1021/ac9000833
Authors: Koo, OK; Liu, Y; Shuaib, S; Bhattacharya, S; Ladisch, M; Bashir, R; Bhunia, A.


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