Impact of enrichment medium on PCR-based detection of Listeria monocytogenes in food | Vpliv obogatitvenega gojišča na določanje bakterij vrste Listeria monocytogenes v živilih s PCR

Inglés.  The detection of Listeria monocytogenes in food samples using enrichment and PCR is described. The objectives were to determine whether the type of enrichment medium has the influence on the results obtained with PCR and to evaluate proposed method by analysing naturally contaminated food samples. Comparative evaluation of different enrichment media for bacteria of the genus Listeria (half Fraser - HF, buffered peptone water - BPW, triptic soy yeast extract broth -  TSBYE, universal preenrichment broth - UPB) showed that only the UPB enabled detection of L. monocytogenes in artificially contaminated food samples after 24h of incubation. The PCR-based method gave equal results as standard cultural method by analysis of naturally contaminated food samples. Described PCR-based procedure is comparable to some other PCR-based methods of L. monocytogenes detection in foods and shows promise as a rapid, routine method which requires 30-72 h, whereas cultural methods require 96-120 h.

Esloveno.  V prispevku je predstavljen postopek določanja bakterij vrste L. monocytogenes v živilih s PCR po obogatitvi vzorca živila. Namen raziskave je bil določiti, ali vrsta obogatitvenega gojišča vpliva na rezultate PCR, in vrednotenje predlagane metode s preiskavami naravno kontaminiranih živil. Primerjava različnih obogatitvenih gojišč za bakterije rodu Listeria (half Fraser - HF, buffered peptone water - BPW, triptic soy yeast extract broth -  TSBYE, universal preenrichment broth - UPB) je pokazala, da edino gojišče UPB omogoča določitev bakterij vrste L. monocytogenes v umetno kontaminiranih vzorcih živil po 24-urni inkubaciji. Rezultati določanja bakterij vrste L. monocytogenes v naravno kontaminiranih vzorcih živil dobljeni po obogatitvi s PCR so bili enaki rezultatom dobljenim s standardno gojitveno metodo. Opisana metoda PCR je primerljiva s podobnimi metodami, ki temeljijo na isti encimski reakciji in omogoča hitro, rutinsko določanje bakterij vrste L. monocytogenes v živilih v 30-72 urah, medtem ko je za rezultate gojitvenih metod potrebno 96-120 ur.