Pavel Pleva

Decarboxylation activity of enterococci isolated from rabbit meat and staphylococci isolated from trout intestines

The aim of the study was to explore production of seven biogenic amines (phenylethylamine, histamine, cadaverine, tyramine, putrescine, spermine and/or spermidine) by selected staphylococci and enterococci. Thirty three enterococcal strains isolated from rabbit meat (Oryctolagus cuniculus f. domesticus) and 21 staphylococcal strains isolated from intestinal content of trout (Salmo trutta morpha fario) were tested. Production of biogenic amines was evaluated after cultivation of the tested microorganisms in the de Man, Rogosa and Sharpe Broth (enterococci) or in the Brain Heart Infusion Broth (staphylococci). Both the above cultivation media were enriched with selected amino acids (histidine, tyrosine, arginine, ornithine and lysine; 2g/L each) serving as precursors of biogenic amines. After cultivation, levels of the monitored biogenic amines in broths were analysed by a high performance liquid chromatography equipped with a UV/VIS DAD detector. Among 21 staphylococci, 18 strains produced tyramine or cadaverine, 13 strains formed putrescine or phenylethylamine and only one strain generated histamine. Two staphylococcal strains produced cadaverine levels above 1000 mg/L. Among 33 enterococcal strains, 27 formed cadaverine, 18 strains produced tyramine, 10 strains generated phenylethylamine, and 2 strains gave putrescine. Most of the tyramine producing enterococci generated more than 1000 mg/L of this biogenic amine. Production of spermine or spermidine by the studied strains was not proved.

Decarboxylase‐positive Enterococcus faecium strains isolated from rabbit meat and their sensitivity to enterocins

Abstract Background The objective of the study was to determine sensitivity of Enterococcus faecium strains from rabbit meat to enterocins. Results Twenty‐five decarboxylase‐positive strains (from rabbit meat) allotted to the species E. faecium by genotypization and by MALDI TOF MS spectrometry identification (evaluation score value range 2.104–2.359; in the range for highly probable species identification‐score value 2.300–3.000 and secure probable species identification/probable species identification‐2.000–2.299) were studied. Seventeen strains were gelatinase positive. Although they did not produce histamine (HIS), spermidine, and spermine, they produce at least one among seven tested biogenic amines (BAs) in small amounts (2–10 mg/L) or up to very high amounts (>1000 mg/L). Putrescine was produced by two strains. These decarboxylase‐positive strains were sensitive to enterocins (Ents). All strains were sensitive to Ent 2019 and Ent 55 (inhibitory activity from 200 to 819 200 AU/mL). Twenty‐two strains were inhibited by Ent A(P) and Ent 4231; 20 strains were sensitive to Ent M. Conclusion Our results have spread the basic knowledge related to inhibitory spectrum of enterocins showing sensitivity of decarboxylase‐positive strains to enterocins. Protective possibilities of enterocins in meat processing were also indicated.

Biogenic amines in smear and mould-ripened cheeses.

The aim of the study was the monitoring of six biogenic amines (histamine, tyramine, phenylethylamine, tryptamine, putrescine, and cadaverine) and two polyamines (spermidine and spermine) in 30 samples of dairy products purchased in the Czech Republic, namely in 15 samples of mould-ripened cheeses and in 15 samples of smear-ripened cheeses. A further goal was the microbiological analysis of the individual samples of cheeses (total count of microorganisms, number of enterobacteria, enterococci, lactic acid bacteria, yeasts and moulds). The monitored biogenic amines were analyzed by a high performance liquid chromatography equipped with a UV/VIS DAD detector. The amount of enterobacteria in fresh cheese exceeded 10 5 CFU.g ‑1 . In smear-ripened cheese flavourless (Romadur type), the amount was >10 3 CFU.g -1 and 10 4 -10 5 CFU.g -1 in smear-ripened cheese with flavour. Biogenic amines were observed in two groups of blue cheeses (white veined cheese and blue veined cheese) and smear-ripened cheeses. In both groups, there is a possibility of the presence of biogenic amines because the number of microorganisms and concentration of free amino acids increase during ripening. In ten samples of soft smear-ripening acid cheese and in smear-ripened cheese, the total content of biogenic amines were 22-1000 mg.kg -1 and in 5 samples of these cheeses, it was in range 1000-6000 mg.kg -1 . The total amount of biogenic amines in the blue cheeses were in range 40-600 mg.kg -1 . The presense of the tyramine was observed in the all analysed cheeses. The tyramine producing strains generated more than 900 mg.kg -1 of this biogenic amine. The production of tryptamine in the analysed cheeses was not proved by this study. The results of this study show that biogenic amines and polyamines are common in cheese. However, in some cases, they can pose a significant health danger for consumers. Any legislative control authority does not monitor them, as they are secondary metabolites even though they are potential health risks.

FACTORS AFFECTED DECARBOXYLATION ACTIVITY OF ENTEROCOCCUS FAECIUM ISOLATED FROM RABBIT

Normal 0 21 false false false SK JA X-NONE Biogenic amines (BA) are basic nitrogenous compounds formed mainly by decarboxylation of amino acids. There are generated in course of microbial, vegetable and animal metabolisms. The aim of the study was to monitor factors affected production of biogenic amines by Enterococcus faecium, which is found in rabbit meat. Biogenic amines were analyzed by means of UPLC (ultrahigh performance liquid chromatography) equipped with a UV/VIS DAD detector. Decarboxylation activity of E. faecium was mainly influenced by the cultivation temperature and the amount of NaCl in this study. E. faecium produced most of the monitored biogenic amines levels: tyramine ˂2500 mg.l -1 ; putrescine ˂30 mg.l -1 ; spermidine ˂10 mg.l -1 and cadaverine ˂5 mg.l -1 . doi:10.5219/182

Characterization of Escherichia coli strains isolated from raw vegetables

Vegetables are an important part of the human diet. Sometimes, contamination by pathogenic Escherichia coli can be underestimated; moreover there is a risk of antibiotic resistance spreading via the food chain. The purpose of this study was to examine the prevalence of Escherichia coli in fresh vegetables sold in retail market in the Czech Republic and to evaluate the risk to human health. Antibiotic resistance against 12 antibiotics, the presence of 12 virulence and 15 resistance genes were determined among 15 isolated strains. Most of tested strains belonged to B1 phylogenetic group, less frequently represented was B2 and D phylogroup. These results indicate that most strains are probably of human origin. All E. coli strains were resistant to at least one of twelve tested antibiotics. A multidrug resistance was observed in four strains. In this study, the presence of virulence factors Einv and papC and also genes encoding toxins (CNF1, CNF2) was detected. Nevertheless, none strain can be considered as STEC or EHEC. The widespread appearance of a growing trend associated with the prevalence of antibiotic resistance among enterobacterial isolates is undeniable and the possibility of transfer to humans cannot be ignored. Nevertheless, these results indicate that raw vegetables sold in the retail market can constitute a potential health risk for consumers.

Biogenic amines content in the fermented asian food in the Czech Republic

Normal 0 21 false false false EN-GB X-NONE X-NONE The aim of this work was to study the typical fermented Asian food (miso paste, soy sauce, rice vinegar, kimchi and tempeh) to monitor their microbial quality and presence of biogenic amines in relation to time and temperature of storage. This study is focused on microbiological research in order to determinate presence of selected indicator groups of microorganisms during storage of individual products at three different temperatures, 8 °C, 23 °C, 30 °C. It was found that the highest increase of total viable counts was observed in products stored in 23 °C and 30 °C, especially in tempeh and miso paste. In soy sauce and rice vinegar were observed only very low amounts of microorganisms through the storage period. In the second part of the experiment, the biogenic amines were analyzed using high performance liquid chromatography. It was found that the levels of biogenic amines in tested products were low and does not affect human health.