Safety Assessment of Enterococcus faecium and Enterococcus faecalis Strains Isolated from Turkish Tulum Cheese

Abstract

The aim of this study was to evaluate several genetic and phenotypic traits of clinical significance in 21 Enterococcus faecium and seven E. faecalis strains previously isolated from Turkish Tulum Cheese. Enterococcus strains were tested for the presence of 14 virulence genes and two vancomycin resistance genes by polymerase chain reaction (PCR). Biogenic amine production was also investigated by decarboxylase medium and PCR. Investigation of virulence factors by PCR amplification revealed the presence of genes encoding for gelatinase (gelE), cell wall adhesin (efaAfm and efaAfs), sex pheromone (ccf), cell wall‐associated protein (espfm and espfs) and aggregation substance (agg). Other presumed virulence genes (cpd, cob, cad, ace, cylM, cylB and cylA) were not detected. At least one virulence gene was detected in all strains. The ccf (85.7%), efaAfm (75.0%) and gelE (32.1%) were detected most frequently present virulence genes in enterococcal strains. Phenotypic gelatinase testing revealed the existence of apparently silent gelE gene. None of the strains carried the vanA and vanB genes. Enterococcus strains did not decarboxylate histidine, lysine or ornithine, but the majority of strains (92.9%) produced tyramine from tyrosine. The tyrosine decarboxylase gene (tdc) was detected in all tyraminogenic strains. Practical Application Enterococci are lactic acid bacteria that are important both in food and clinical microbiology. Enterococci species especially E. faecium and E. faecalis play an important role in the development of sensory characteristics of different traditional fermented foods such as dairy and meat products. On the other hand, E. faecium and E. faecalis are recognized as nosocomial pathogens. Results of this study indicated that E. faecium and E. faecalis strains isolated from Turkish Tulum Cheese carried some virulence genes and most of them produce tyramine. The findings of our study suggest that E. faecium and E. faecalis strains isolated from Turkish Tulum Cheese may be potential risk factors for consumer health. For this reason, use of Enterococcus strains as starter cultures requires thorough safety evaluation.

Determination of antibiotic susceptibility and decarboxylase activity of coagulase-negativeStaphylococcusandMacrococcus caseolyticusstrains isolated from fermented Turkish sausage (sucuk)

“…PCR experiments confirmed the amino acid decarboxylase medium results. It was determined that there is a 100% correlation between tyramine production and presence of tdc gene, as previously reported by Kalhotka et al () and Inoglu and Tuncer ().…”

Antimicrobial Activity, Antibiotic Resistance and the Safety of Lactic Acid Bacteria in Raw Milk Valtellina Casera Cheese

“…; Martín‐Platero et al . ; Inoğlu and Tuncer ). Nevertheless, with the exception of hyl and cyl A, these antigens should not be considered as true virulence determinants but rather as auxiliary factors associated with colonization abilities, promoting the persistence of the bacterium in the gastrointestinal tract and hence demonstrating its potential probiotic properties (Vankerckhoven et al .…”

Determination of Antibiotic Resistance and Biogenic Amine Production of Lactic Acid Bacteria Isolated from Fermented Turkish Sausage (Sucuk)

“…After 7 days of aerobic incubation, BA production of the isolates was determined phenotypically by yellow to purple color changes in the Petri dishes. Tyraminogenic E. faecium NYE54 strain obtained from Inoğlu and Tuncer () was used as the positive control.…”

“…Several genera among LAB may produce BA by decarboxylation of amino acids, e.g., Lactobacillus, Carnobacterium , Pediococcus , Lactococcus , Enterococcus and Leuconostoc (Silla‐Santos ; Suzzi and Gardini ; Komprda et al . ; Inoğlu and Tuncer ).…”