Detection of Listeria innocua by acoustic aptasensor

Early detection of foodborne pathogens is significant for ensuring food safety. Nowadays, the detection of pathogens found in food can take up to 72 hours and it might take a week to confirm positive sample. While standardized methods give test results in a shorter period of time, the reoccurring costs for each measurement are high. That is why it is necessary to develop technology that will be cheap, fast, simple and accurate enough. Biosensors in combination with aptamers offer such possibilities.

This work is focused on the development and testing of a biosensor based on DNA aptamers for detection of pathogenic bacteria Listeria innocua using the method of quartz crystal microbalances (QCM). The aptasensor was formed on the surface of an oscillating piezo crystal, whose frequency was affected by deposited mass. An aptamer specific to the genus Listeria spp was used for detection of pathogen, which includes 16 subspecies. 3 subspecies are excluded as their antigen structure differs from other species (L. murrayi, L. grayi, L. ivanovii).

We found that when Listeria innocua cells interacted with an aptamer specific for Listeria spp. Addition of the pathogens at the QCM transducer modified by aptamers resulted in decrease of the resonant frequency in concentration depending manner. We also confirmed the specificity of the aptamer used for Listeria innocua, as neglected response of the sensor took place for E. coli for which Listeria spp. has some partial antigens identical and thus can cause cross-reactions in serological tests. The developed aptasensor showed promising sensitivity and specificity for real-time detection of Listeria innocua, with a detection time of 30 min. The achieved limit of detection was approximately 1.6 x 10³ CFU / ml.

Acknowledgement

This work was funded by the European Union, project Horizon 2020, Marie Skłodowska-Curie, contract number 690898 and was also supported by the scientific grant agency VEGA, project number: 1/0419/20.