title: Safety evaluation in vitro of Enterococcus durans from Tibetan traditional fermented yak milk.
abstract: Despite its ubiquity in fermented dairy products, the safety of lactic acid enterococcal bacteria remains controversial. In this study, five Enterococcus durans strains - A1, A2, B1, B2, and C1 - were isolated from traditional fermented yak milk from Tibet. To evaluate the strains' safety, biogenic amine production, antibiotic resistance and presence of known virulence determinants were investigated. Strain A1 can produce biogenic amines for histamine, spermine, and spermidine (mean values: 8.64, 8.31, and 0.30 mg/L, respectively). Polymerase chain reaction amplification for Strain A1 found genes involved in expression of gelatinase (gleE), cytolysin (cylA, cylB, and cylM), sex pheromones (ccf and cpd) and cell wall adhesion (efaA). Strain A2 showed sensitivity or intermediate resistance to all tested antibiotics, and no virulence determinants except gelE and ccf, but did produce tyramine at a relatively high level (912.02 mg/L). Both strains B1 and B2 could produce histamine (10.43 and 10.56 mg/L, respectively), and showed vancomycin resistance; B1 also produced tyramine (504.02 mg/L). Strain C1 could produce all five biogenic amines tested in the study -putrescine, histamine, tyramine, spermine, and spermidine; concentrations were 6.51, 9.59, 205.85, 5.55, and 5.39 mg/L, respectively. All E. durans strains found in Tibetan traditional fermented yak milk thus offer potential risk.
authors: College of Food Science and Technology Engineering, Gansu Agricultural University, Lanzhou, 730070, P. R. China.
authors: Jing
authors: J
authors: Li
authors: Fazheng
authors: F
authors: Ren
authors: Huiyong
authors: H
authors: Gu
authors: Xiaopeng
authors: X
authors: Li
authors: Bozhong
authors: B
authors: Gan
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001679:Biogenic Amines / Q000378:metabolism; D002417:Cattle; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D016983:Enterococcus / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism / Q000502:physiology*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D018609:Tibet; D037521:Virulence Factors / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001679:Biogenic Amines; D004269:DNA, Bacterial; D037521:Virulence Factors