Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom BT9 7BL.
Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom BT9 7BL.
J Dairy Sci. 2017 Dec;100(12):9723-9735. doi: 10.3168/jds.2017-13154. Epub 2017 Oct 4.
When advising farmers on how to control Johne's disease in an infected herd, one of the main recommendations is to avoid feeding waste milk to calves and instead feed calf milk replacer (CMR). This advice is based on the assumption that CMR is free of viable Mycobacterium avium ssp. paratuberculosis (MAP) cells, an assumption that has not previously been challenged. We tested commercial CMR products (n = 83) obtained from dairy farms around the United States by the peptide-mediated magnetic separation (PMS)-phage assay, PMS followed by liquid culture (PMS-culture), and direct IS900 quantitative PCR (qPCR). Conventional microbiological analyses for total mesophilic bacterial counts, coliforms, Salmonella, coagulase-negative staphylococci, streptococci, nonhemolytic Corynebacterium spp., and Bacillus spp. were also performed to assess the overall microbiological quality of the CMR. Twenty-six (31.3%) of the 83 CMR samples showed evidence of the presence of MAP. Seventeen (20.5%) tested positive for viable MAP by the PMS-phage assay, with plaque counts ranging from 6 to 1,212 pfu/50 mL of reconstituted CMR (average 248.5 pfu/50 mL). Twelve (14.5%) CMR samples tested positive for viable MAP by PMS-culture; isolates from all 12 of these samples were subsequently confirmed by whole-genome sequencing to be different cattle strains of MAP. Seven (8.4%) CMR samples tested positive for MAP DNA by IS900 qPCR. Four CMR samples tested positive by both PMS-based tests and 5 CMR samples tested positive by IS900 qPCR plus one or other of the PMS-based tests, but only one CMR sample tested positive by all 3 MAP detection tests applied. All conventional microbiology results were within current standards for whole milk powders. A significant association existed between higher total bacterial counts and presence of viable MAP indicated by either of the PMS-based assays. This represents the first published report of the isolation of viable MAP from CMR. Our findings raise concerns about the potential ability of MAP to survive manufacture of dried milk-based products.
在向受感染牛群的农场主提供有关如何控制约翰氏病的建议时，主要建议之一是避免用废奶喂养小牛，而改用牛犊代乳粉（CMR）。该建议基于这样的假设，即 CMR 不含活的分枝杆菌 avium ssp. paratuberculosis（MAP）细胞，这一假设以前从未受到过质疑。我们通过肽介导的磁分离（PMS）-噬菌体检测、PMS 后液体培养（PMS-culture）和直接 IS900 定量 PCR（qPCR），对从美国各地的奶牛场获得的商业 CMR 产品（n=83）进行了检测。还进行了常规微生物分析，用于检测总需氧细菌计数、大肠菌群、沙门氏菌、凝固酶阴性葡萄球菌、链球菌、非溶血性棒状杆菌和芽孢杆菌，以评估 CMR 的整体微生物质量。83 个 CMR 样本中有 26 个（31.3%）显示出存在 MAP 的证据。17 个（20.5%）通过 PMS-噬菌体检测呈活的 MAP 阳性，再制 CMR 中的噬菌斑计数范围为 6 至 1,212 pfu/50 mL（平均 248.5 pfu/50 mL）。12 个（14.5%）CMR 样本通过 PMS 培养呈活的 MAP 阳性；从所有 12 个样本中分离出的菌株随后通过全基因组测序被确认为不同的 MAP 牛株。7 个（8.4%）CMR 样本通过 IS900 qPCR 检测出 MAP DNA 阳性。4 个 CMR 样本通过基于 PMS 的两种检测方法均呈阳性，5 个 CMR 样本通过 IS900 qPCR 加一种或另一种基于 PMS 的检测方法呈阳性，但只有一个 CMR 样本通过应用的 3 种 MAP 检测方法均呈阳性。所有常规微生物学结果均符合全脂奶粉的现行标准。基于 PMS 的两种检测方法中的任何一种检测到活的 MAP 存在时，总细菌计数较高与该结果存在显著关联。这是首次报道从 CMR 中分离出活的 MAP。我们的研究结果引起了对 MAP 可能有能力在干奶基产品制造过程中存活的关注。
