Edrington T S, Loneragan G H, Genovese K J, Hanson D L, Nisbet D J
U.S. Department of Agriculture, Agricultural Research Service, Food and Feed Safety Research Unit, 2881 F&B Road, College Station, Texas 77845, USA.
International Center for Food Industry Excellence, Department of Animal and Food Sciences, P.O. Box 42141, Texas Tech University, Lubbock, Texas 79409, USA.
J Food Prot. 2016 Jun;79(6):1032-5. doi: 10.4315/0362-028X.JFP-15-325.
Utilizing a transdermal method of inoculation developed in our laboratory, the duration of infection of Salmonella in the peripheral lymph nodes of steers was examined. Thirty-six Holstein steers (mean body weight of 137 kg) were inoculated with Salmonella Montevideo (day 0) on each lower leg and both sides of the back and abdomen. Calves were euthanized beginning at 6 h and subsequently on each of days 1, 2, 4, 7, 9, 11, 14, and 21 postinoculation (four animals each time). The subiliac, popliteal, and superficial cervical (prescapular) lymph nodes were collected and cultured (quantitatively and qualitatively) for the challenge strain of Salmonella. The challenge strain was detected via direct culture within the lymph nodes at 6 h postinoculation and on each subsequent necropsy date. Salmonella levels in lymph node were 0.8 to 1.8 log CFU/g. Lymph nodes were generally positive after enrichment culture throughout the experiment. Salmonella elimination appeared to begin approximately 14 days postinoculation. However, elimination was not completed by day 21; therefore, a second experiment was conducted identical to the first except that the time from inoculation to necropsy was extended. Salmonella was recovered via direct culture on each of the necropsy days, and results in general were similar to those of experiment I, except that on days 20, 24, and 28 isolates from serogroups C2 and E1 were identified in addition to the inoculation strain C1 in multiple animals. The data from both experiments indicate that after a single inoculation event, Salmonella would be completely cleared by approximately 28 days. Further research with expanded times between inoculation and necropsy is required for verification.
利用我们实验室开发的经皮接种方法，对公牛外周淋巴结中沙门氏菌的感染持续时间进行了研究。36头荷斯坦公牛（平均体重137千克）在每条小腿以及背部和腹部两侧接种蒙得维的亚沙门氏菌（第0天）。从接种后6小时开始，随后在接种后的第1、2、4、7、9、11、14和21天，每次对4头小牛实施安乐死。收集髂下、腘和浅表颈（肩胛前）淋巴结，并对沙门氏菌攻击菌株进行（定量和定性）培养。在接种后6小时以及随后每次尸检时，通过淋巴结直接培养检测攻击菌株。淋巴结中的沙门氏菌水平为0.8至1.8 log CFU/g。在整个实验过程中，富集培养后淋巴结通常呈阳性。沙门氏菌的清除似乎在接种后约14天开始。然而，到第21天时清除尚未完成；因此，进行了与第一个实验相同的第二个实验，只是将接种到尸检的时间延长。在每次尸检日通过直接培养回收沙门氏菌，总体结果与实验I相似，只是在第20、24和28天，除了接种菌株C1外，在多只动物中还鉴定出了血清群C2和E1的分离株。两个实验的数据均表明，单次接种后，沙门氏菌大约在28天内会被完全清除。需要进行进一步研究，扩大接种与尸检之间的时间间隔以进行验证。
