Department of Microbiology, Universitry Campus, State University of Londrina, Londrina, Brazil.
Department of Food Technology, Campus of Londrina, Federal Technological University of Paraná, Londrina, Brazil.
J Environ Sci Health B. 2019;54(12):925-929. doi: 10.1080/03601234.2019.1647753. Epub 2019 Aug 5.
Dissemination of vancomycin resistance in enterococci has been associated with horizontal transfer of mobile genetic elements. Aim of the study was to evaluate if milk matrix is a suitable environment to support transferability of vancomycin resistance (A) gene from clinical vancomycin-resistant to vancomycin-sensitive . Enterococci strains were firstly screened for the presence of (inducible sex pheromone determinant) gene, A and L genes (vancomycin and tetracycline resistance markers, respectively) and the E (extracellular metalloendopeptidase) gene to define the mating pairs. Based on these selection markers, we investigated the transferability of eight plasmid-borne A harbored by (A+, -L and E-) into two (A-, +L + and E+) recipient strains in milk matrix. The strains were mated in a 1:1 ratio in 7% reconstituted milk and incubated at 37 °C. Transconjugants emerged from all 16 matings within 2 h of incubation and were evidenced by dual antibiotic resistance (vancomycin and tetracycline). The vancomycin-resistance of trasconjugants was maintained even after ten subsequent passages on nonselective medium. Transconjugants were positive for A, L and E genes. This study indicates milk matrix as suitable environment to support gene exchange between species.
肠球菌中万古霉素耐药性的传播与可移动遗传因子的水平转移有关。本研究旨在评估牛奶基质是否是支持临床万古霉素耐药肠球菌将万古霉素耐药（A）基因转移至万古霉素敏感肠球菌的合适环境。首先筛选肠球菌菌株中是否存在（诱导性性信息素决定因子）基因、A 和 L 基因（分别为万古霉素和四环素耐药标记物）和 E（细胞外金属内肽酶）基因，以确定交配对。基于这些选择标记，我们研究了 8 株质粒携带的 A 基因在牛奶基质中从（A+、-L 和 E-）转移到 2 株（A-、+L+和 E+）受体菌株的可转移性。将菌株以 1:1 的比例在 7%重组牛奶中交配，并在 37°C 下孵育。在孵育 2 小时内，所有 16 次交配中均出现了转导子，并且通过双重抗生素耐药性（万古霉素和四环素）得到证实。即使在非选择性培养基上进行了十次后续传代，转导子的万古霉素耐药性仍得以维持。转导子对 A、L 和 E 基因呈阳性。本研究表明牛奶基质是支持 种间基因交换的合适环境。
