Tyramine-producing enterococci are equally detected on tyramine production medium, by quantification of tyramine by HPLC, or by tdc gene-targeted PCR.

摘要

Presence of biogenic amines (BA) in foods is not acceptable as the consumption of food and beverages containing high levels of BA could result in toxicological effects upon human health. BA are mainly produced by the microbial decarboxylation of certain amino acids. Among the various BA, tyramine is one of the most commonly cited and abundant, produced by several bacterial genera. Various biochemical, chromatographic and molecular methods are used for the detection of BA. Among different lactic acid bacteria, enterococci have been found to be abundant tyramine producers. Thus, 28 dairy-derived bacteriocinogenic strains of Enterococcus spp. were tested for their ability to produce tyramine by qualitative, quantitative and molecular methods. Correlations between these methods were also investigated. A total of 19 enterococcal strains were found to produce tyramine by all the methods used. A low level of correlation was found between the results of 2 different decarboxylating media (improved medium and tyrosine production medium; TPM). Improved medium detected more tyrosine-positive colonies than TPM. However, 100% correlation was observed between the results observed with TPM, tdc gene-targeted PCR and tyramine quantification using HPLC. It is suggested that these methods could be used to complement each other in the detection of tyramine-producing enterococci in foods.