Electrochemical DNA biosensor for rapid detection of Listeria monocytogenes in meat samples

Introduction: Listeriosis, a zoonosis caused by the consumption of food contaminated with L. monocytogenes, shows the highest fatality rate in Europe. Official methods are laborious and time-consuming; moreover, an underestimation of the microorganism number is possible due to a viable but non-culturable (VBNC) state. Vibrio cholerae, E. coli, Campylobacter jejuni, Salmonella spp., Listeria monocytogenes, and Yersinia enterocolitica have been identified in the VBNC state, highlighting the importance of specific detection of L. monocytogenes. Materials and methods: A biosensor based on a screen-printed gold electrode coupled to voltammetry analysis of the redox couple ferrocyanide/ferricyanide was used. The bio-recognition element was a DNA probe (ListE) designed to detect L. monocytogenes and previously tested with the dot blot technique. The differential pulse voltammetry technique was adopted for the analysis of genomic DNA, raw meat and industrial environmental samples. The AFNOR (French Association for Standardization) validated Listeria Precis™ method (Thermo Scientific, Basingstoke, UK) was also used to verify the presence of the target microorganism. Results: The electrochemical biosensor showed a good linear response between signal decrement and the amount of target hybridized on the electrode both in ListE complementary sequence, used as a control, and in DNA extracted from pure cultures. The system showed a good performance when utilized for analyses on raw meat and industrial environmental samples comparing the outcomes with the results produced with the AFNOR validated Listeria Precis™ method. Conclusions: Considering these preliminary results, the biosensor represents a promising tool for the detection of L. monocytogenes that is rapid, easy to use and cheap, although some aspects need to be further investigated.