Výskumný ústav potravinársky

Minarovičová, J. – Véghová, A. – Kaclíková, E.
Evaluation of immunomagnetic separation and polymerase chain reaction for culture-independent detection of Listeria monocytogenes low numbers in cheese


Eva Kaclíková, Department of Microbiology, Molecular Biology and Biotechnology, Food Research Institute, National Agricultural and Food Centre, Priemyselná 4, 82475 Bratislava, Slovakia. E-mail: eva.kaclikova@nppc.sk

Received 11 February 2020; 1st revised 6 April 2020; accepted 4 May 2020; published online 14 May 2020.

Súhrn: Listeria monocytogenes continues to be a major food-borne bacterial pathogen. Therefore, an improvement of rapid and reliable methods for its detection in food is still required. In our study, a potential of immunomagnetic separation (IMS) for culture-independent determination of low numbers of L. monocytogenes in cheese was evaluated. IMS using Dynabeads anti-Listeria (Thermo Fischer Scientific, Waltham, Massachusetts, USA) followed by simple thermal cell lysis and specific real-time polymerase chain reaction (PCR) was applied to various steamed cheeses artificially contaminated with L. monocytogenes strains. The described protocol was applied to six smoked and non-smoked steamed cheese products artificially contaminated at L. monocytogenes calculated levels ranging from 8.8 x 10⁴ CFU.g^-1 to 2.2 x 10¹ CFU.g^-1. Results were obtained in five hours with PCR detection limit of L. monocytogenes numbers (3.8–7.4) × 10² CFU.g^-1 as estimated in individual artificially contaminated test portions. An additional step of 5-fold concentration of the filtered sample homogenate by centrifugation prior to IMS improved the detection to the level of (1.6–2.0) × 10² CFU.g^-1 with no negative effect due to relatively higher content of natural microflora in cheese made from raw milk. The evaluated procedure proved to be a fast method for L. monocytogenes low numbers detection in cheese.

Kľúčové slová: Listeria monocytogenes, cheese, immunomagnetic separation, polymerase chain reaction, culture-independent detection

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