LISTERIA KNOWLEDGE STRENGTHENED Despite the high standards of cleanliness and hygiene in the food industry, Bacteria such as Listeria monocytogenes can still be found in food processing environments undergoing high standards of cleanliness and hygiene. A study published in Applied and Environmental 20 OCTOBER 2017 Microbiology by a team of Vetmeduni Vienna researchers found that certain Listeria strains take ‘refuge on an island’ made up of two genes located in one area of the genome, which increases the bacteria’s survival under alkaline and oxidative stress conditions. The team was able to identify the two genes as a functional unit termed a ‘stress survival islet’, and first author Eva Harter says understanding this genetic ‘lifesaver’ can help develop new strategies for food safety. Listeria monocytogenes is a foodborne pathogen that colonises and reproduces on diverse food products including cheese or meat, and without proper food hygiene, it represents a health risk. Hygiene standards in food production chains are therefore high, but Listeria is known for its ability to survive in environmental niches in which other microorganisms cannot, Harter says. “The key to the bacteria’s survival is its adaptability and persistence in stress situations. Certain genetic mechanisms allow L. monocytogenes to react to and block the effects of cleaning solutions and disinfectants.” Researchers from the Institute of Milk Hygiene were able to decipher this function for two of the food pathogen’s genes. They showed that these genes form a functional unit that ensures the bacteria’s survival despite the hygiene standards in the food production industry. Hypervariable (easily changeable) regions of the genome contain genetic inserts that help Listeria survive. “These inserts include a unit of gene sequences, the stress survival islet 1 (SSI-1), a ‘genomic island’ that helps the microorganisms to survive certain stress situations,” Harter says. “Depending on the specific bacterial strain, this region accommodates one of three different gene sequences whose function, with the exception of SSI-1, had so far not been known.” The genes in the stress survival islet 1 confer the bacteria a high tolerance toward acidic, bile, salt and gastric stresses, which has been characterised for years. However, Harter says this does not explain how the bacteria can survive the hygiene standards in the food processing industry, which involves different, namely alkaline and oxidative, stress situations for Listeria. The researchers therefore concentrated on two neighbouring gene sequences within the same hypervariable region, and were able to identify these as Gribbles Labnet: providing tailored solutions for all your food and environmental testing needs » Microbiology » Analytical chemistry » Pathogen testing » Nutritional analysis » Shelf life testing » Vitamins » Allergens » Hygiene monitoring » Elemental analyses Feed and meal (including meat and bone meal, blood meal, fish meal and feather meal) testing services also available. www.gribbleslabnet.co.nz sales@gribbleslabnet.co.nz 0800 GRIBBLES FT384 Talk to us about our real-time pathogen testing with new GENE-UP® PCR technology. • Fast detection of Salmonella, Listeria spp. and Listeria monocytogenes - in just one day • Dual detection using FRET technology and Melt analysis • Less false positive screen results Choose the test that you can trust. GENE-UP® is IANZ accredited and approved under MPI Recognised Laboratory Programme for export testing. Tel. 0508 00 11 22 www.asurequality.com FT339 MICROBIOLOGY
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