腹泻是全球新生儿和幼牛的主要健康问题。它可能是由多种传染因子引起的,包括都柏林肠道沙门氏菌(S.Dublin),产肠毒素大肠杆菌(ETEC),和产气荚膜梭菌.应确定抗生素治疗的预防性替代方案。作为迈向这一步的第一步,本研究的目的是检查由乳酸菌发酵的牛奶的无细胞上清液是否会影响都柏林菌株的毒力基因表达,ETEC大肠杆菌F5和产气荚膜梭菌。pH中和,无细胞,测定了由61种不同的乳酸菌(LAB)和属于17个属的非LAB发酵剂培养物发酵的牛奶(nCFSM)的废培养基对重要毒力因子表达的影响(S.都柏林hilA,ssrB,ssaG,flhD,prgI,F5fanC,estA,fim41a;产气荚膜梭菌cpa),当细菌在nCFSM中生长时。使用启动子-报告基因表达系统或RT-qPCR进行筛选。来自长双歧杆菌BL-15955和罗伊利氏杆菌LR-33016的nCFSM下调fanC的表达,fim41a和estA基因在四个测试的ETEC大肠杆菌F5菌株不影响其生长,而主要是长芽孢杆菌BL-15955下调了四株产气荚膜梭菌中cpa的表达。来自混合培养物的nCFSM;NU-TRISH®BY-Mild(德氏乳杆菌亚种。保加利亚,嗜热链球菌和双歧杆菌BL-15954)和COMBO4(德氏乳杆菌亚种。保加利亚和嗜热链球菌),以及瑞士乳杆菌CNRZ32下调了三个测试的都柏林菌株中测试的毒力基因。为了能够同时下调所有三种靶细菌中毒力基因的表达,nCFSM由NU-TRISH®By-Mild与长双歧杆菌BL-15955组合(即四菌株组合)制备。来自该组合的nCFSM下调了所有三个物种中的毒力基因表达。在未来,NU-TRISH®By-Mild和B.longumBL-15955的组合可用于预防由S.Dublin引起的新生儿小牛腹泻,大肠杆菌F5和产气荚膜梭菌,减少对抗菌治疗的需要,然而,需要实地研究来证明这一点。
Diarrhea is a major health problem in neonatal and young calves worldwide. It can be caused by a variety of infectious agents, including the bacteria Salmonella enterica serovar Dublin (S. Dublin), enterotoxigenic Escherichia coli (ETEC), and Clostridium perfringens. Preventive alternatives to antibiotic treatment should be identified. As a first step toward this, the aim of the current study was to examine whether cell-free supernatants from cow milk fermented by lactic acid bacteria affects virulence-gene expression in strains of S. Dublin, ETEC E. coli F5 and C. perfringens. pH-neutralized, cell-free, spent medium of milk (nCFSM) fermented by 61 different lactic acid bacteria (LAB) and non-LAB starter cultures belonging to 17 genera was assayed for their effect on expression of important virulence factors (S. Dublin hilA, ssrB, ssaG, flhD, prgI, fliC; ETEC E. coli F5 fanC, estA, fim41a; C. perfringens cpa), when the bacteria were grown in the nCFSM. Screening was done using either a promoter-reporter expression system or RT-qPCR. nCFSM from Bifidobacterium longum BL-15955 and Limosilactobacillus reuteri LR-33016 downregulated the expression of fanC, fim41a and estA genes in the four tested ETEC E. coli F5 strains without affecting their growth, while mainly B. longum BL-15955 downregulated expression of cpa in the four tested strains of C. perfringens. nCFSM from the mixed cultures; NU-TRISH® BY-Mild (Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus and Bifidobacterium BL-15954) and COMBO4 (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus), as well as Lactobacillus helveticus CNRZ32 downregulated the tested virulence genes in the three tested strains of S. Dublin. To enable possible downregulation of the expression of virulence genes in all three target bacteria simultaneously, nCFSM was prepared from NU-TRISH® By-Mild in combination with B. longum BL-15955 (i.e. a four-strain combination). The nCFSM from this combination downregulated the virulence genes expression in all the three species. In the future, NU-TRISH® By-Mild and B. longum BL-15955 in combination could potentially be used for prevention of neonatal calf diarrhea caused by S. Dublin, E. coli F5, and C. perfringens, reducing the need for antimicrobial treatment, however, field studies are needed to prove that.