Agriculture and Agri-Food Canada, Lethbridge Research Centre, 5403 1 Avenue South, P,O, Box 3000, T1J 4B1 Lethbridge, AB, Canada.
Ir Vet J. 2013 Oct 3;66(1):17. doi: 10.1186/2046-0481-66-17.
In the less-sensitive mouse model, Shiga toxin-producing Escherichia coli (STEC) challenges result in shedding that reflect the amount of infection and the expression of virulence factors such as Shiga toxins (Stx). The purpose of this study was to characterize the contribution of STEC diversity and Stx expression to shedding in beef feeder calves and to evaluate the effectiveness of a prebiotic, Celmanax®, to alleviate STEC shedding. Fecal samples were collected from calves at entry and after 35 days in the feedlot in spring and summer. STECs were evaluated using selective media, biochemical profile, serotyping and Stx detection. Statistical analysis was performed using repeated measures ANOVA and logistic regression.
At entry, non-O157 STEC were dominant in shedding calves. In spring, 21%, 14% and 14% of calves acquired O157, non-O157 and mixed STEC infections, respectively. In contrast, 45%, 48% and 46% of calves in summer acquired O157, non-O157 and mixed STEC infections, respectively. Treatment with a prebiotic, Celmanax®, in spring significantly reduced 50% of the O157 STEC infections, 50% of the non-O157 STEC infections and 36% of the STEC co-infections (P = 0.037). In summer, there was no significant effect of the prebiotic on STEC infections. The amount of shedding at entry was significantly related to the number and type of STECs present and Stx expression (r2 = 0.82). The same relationship was found for shedding at day 35 (r2 = 0.85), but it was also related to the number and type of STECs present at entry. Stx - producing STEC infections resulted in 100 to 1000 × higher shedding in calves compared with Stx-negative STECs.
STEC infections in beef feeder calves reflect the number and type of STECs involved in the infection and STEC expression of Stx. Application of Celmanax® reduced O157 and non-O157 STEC shedding by calves but further research is required to determine appropriate dosages to manage STEC infections.
在敏感性较低的小鼠模型中，产志贺毒素大肠杆菌（STEC）感染会导致脱落，反映感染程度和志贺毒素（Stx）等毒力因子的表达。本研究的目的是描述 STEC 多样性和 Stx 表达对育肥牛犊脱落的贡献，并评估益生元 Celmanax®减轻 STEC 脱落的效果。在春季和夏季，在牛只进入育肥场和 35 天后采集粪便样本。使用选择性培养基、生化特征、血清型和 Stx 检测来评估 STEC。使用重复测量方差分析和逻辑回归进行统计分析。
在进入时，非 O157 STEC 在脱落牛中占主导地位。在春季，分别有 21%、14%和 14%的牛获得了 O157、非 O157 和混合 STEC 感染。相比之下，在夏季，分别有 45%、48%和 46%的牛获得了 O157、非 O157 和混合 STEC 感染。在春季使用益生元 Celmanax®治疗可显著降低 50%的 O157 STEC 感染、50%的非 O157 STEC 感染和 36%的 STEC 混合感染（P=0.037）。在夏季，益生元对 STEC 感染没有显著影响。进入时的脱落量与存在的 STEC 数量和类型以及 Stx 表达显著相关（r2=0.82）。在第 35 天的脱落时也发现了同样的关系（r2=0.85），但它也与进入时存在的 STEC 数量和类型有关。与 Stx 阴性 STEC 相比，产 Stx 的 STEC 感染导致牛的脱落量增加了 100 到 1000 倍。
育肥牛犊中的 STEC 感染反映了感染中涉及的 STEC 数量和类型以及 Stx 的 STEC 表达。应用 Celmanax®可减少牛犊中 O157 和非 O157 STEC 的脱落，但需要进一步研究确定适当的剂量来管理 STEC 感染。
