Control of Escherichia coli O157:H7 in contaminated alfalfa silage: Effects of silage additives
Control of Escherichia coli O157:H7 in contaminated alfalfa silage: Effects of silage additives
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DOI：
10.3168/jds.2015-10766
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发表时间：
2016-06-01
影响因子：
3.5
通讯作者：
Adesogan, A. T.
中科院分区：
文献类型：
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作者：
Ogunade, I. M.;Kim, D. H.;Adesogan, A. T.
本研究旨在研究在受大肠杆菌O 157：H7污染的苜蓿青贮饲料中添加微生物菌剂或丙酸是否会抑制青贮期间或之后病原菌的生长。在开花初期收获苜蓿草，使其枯萎至干物质浓度为54%，切碎至19-mm长，并在用以下之一处理后青贮：（1）蒸馏水（对照）;（2）1 × 10（5）cfu/g E.大肠杆菌O 157：H7（EC）;（3）EC和1 × 106 cfu/g植物乳杆菌（EC+LP）;（4）EC和1 × 106 cfu/g布氏乳杆菌（EC+LB）;和（5）EC和2.2 g/kg丙酸（EC+PA）。每种处理在实验室青贮窖中进行0、3、7、16和100 d的四倍青贮，并分析EC计数、pH和有机酸。此外，分析了d 100的样品的化学成分、氨氮、酵母菌和霉菌计数以及有氧稳定性。大肠杆菌O 157：H7检测到所有青贮饲料中，直到第7天，但到第16天，它没有检测到在那些与EC+LB和EC+LP处理，虽然它仍然检测到EC和EC+PA青贮饲料。然而，到d 100，在任何青贮饲料中均未检测到病原体。pH下降至5.0的速度以EC+LP青贮最快（7 d），其次是EC+LB青贮（16 d）。然而，所有青贮饲料已达到pH值或小于5.0的d 100。EC+LP和EC+LB青贮饲料中的pH值的快速下降，观察到由于较高的乳酸盐和乙酸盐浓度，分别相对于其他青贮饲料在早期发酵阶段（d 3-16）。丙酸仅在EC+PA青贮中检测到。EC+LB和EC+PA青贮饲料中酵母菌数最低。所有d-100青贮饲料的子样品在筒仓打开后立即用1 x 10（5）cfu/g EC重新接种。当病原体随后计数后168小时的有氧暴露，它没有检测到在青贮饲料处理EC+PA，EC+LB，或EC+LP，其pH值均小于5.0。而EC青贮饲料的pH值为5.4，病原菌为2.3 log cfu/g。某些细菌接种剂能加速对大肠杆菌的抑制作用。coli O 157：H7，如丙酸等，也可防止其在青贮后被病原菌污染的青贮饲料上生长。
This study was conducted to examine if adding microbial inoculants or propionic acid to alfalfa silages contaminated with Escherichia coli O157:H7 would inhibit the growth of the pathogen during or after ensiling. Alfalfa forage was harvested at the early bloom stage, wilted to a dry matter concentration of 54%, chopped to 19-mm lengths, and ensiled after treatment with one of the following:(1) distilled water (control); (2) 1 x 10(5) cfu/g of E. coli O157:H7 (EC); (3) EC and 1 x 10(6) cfu/g of Lactobacillus plantarum (EC+LP); (4) EC and 1 x 10(6) cfu/g of Lactobacillus buchneri (EC+LB); and (5) EC and 2.2 g/kg of propionic acid (EC+PA). Each treatment was ensiled in quadruplicate in laboratory silos for 0, 3, 7, 16, and 100 d and analyzed for EC counts, pH, and organic acids. In addition, samples from d 100 were analyzed for chemical composition, ammonia-N, counts of yeasts and molds, and aerobic stability. Escherichia coli O157:H7 was detected in all silages until d 7, but by d 16 it was not detected in those treated with EC+LB and EC+LP, though it was still detected in EC and EC+PA silages. However, by d 100, the pathogen was not detected in any silage. The rate of pH decrease to 5.0 was fastest for the EC+LP silage (7 d), followed by the EC+LB silage (16 d). Nevertheless, all silages had attained a pH of or less than 5.0 by d 100. The rapid decrease in pH in EC+LP and EC+LB silages was observed due to higher lactate and acetate concentrations, respectively, relative to the other silages during the early fermentation phase (d 3-16). Propionic acid was only detected in the EC+PA silage. Yeast counts were lowest in EC+LB and EC+PA silages. Subsamples of all d-100 silages were reinoculated with 1 x 10(5) cfu/g of EC immediately after silo opening. When the pathogen was subsequently enumerated after 168 h of aerobic exposure, it was not detected in silages treated with EC+PA, EC+LB, or EC+LP, which all had pH values less than 5.0. Whereas the EC silage had a pH value of 5.4 and 2.3 log cfu/g of the pathogen. Certain bacterial inoculants can hasten the inhibition of E. coli O157:H7 during ensiling, such as propionic acid, and they can also prevent its growth on silage contaminated with the pathogen after ensiling.