IEH Laboratories and Consulting Group, 15300 Bothell Way N.E., Lake Forest Park, WA 98155, USA.
J Food Prot. 2012 Aug;75(8):1464-8. doi: 10.4315/0362-028X.JFP-11-540.
The objective of this study was to determine the source(s) of Salmonella contamination in ground beef. One hundred dairy cows were harvested in a U.S. commercial beef processing plant. Samples of hides, carcasses after hide removal and before exposure to antimicrobial intervention, carcasses after all antimicrobial interventions, superficial cervical lymph nodes from the chuck, trim, ground beef, and air were obtained. Ninety-six percent of the hide samples, 47% of the carcasses before intervention, 18% of the lymph nodes, 7.14% of the trim, and 1.67% of the ground beef samples were positive for Salmonella. None of the samples obtained from the carcasses after the full complement of interventions and none of the air samples were positive for Salmonella. All Salmonella-positive samples were subjected to pulsed-field gel electrophoresis, and eight DNA Xba I restriction patterns were identified. The majority of isolates had one of two restriction digest patterns. The strain isolated from ground beef had the same pattern as the strains isolated from hides and from carcasses immediately after hide removal. The Salmonella isolates from trim samples and lymph nodes also had the same restriction digest pattern. These results indicate that hide and lymph nodes are the most likely sources of Salmonella in ground beef. Dressing practices that effectively reduce or eliminate the transfer of bacteria from hide to carcass and elimination of lymph nodes as a component of raw ground beef should be considered as measures to reduce Salmonella contamination of ground beef. Because total elimination of lymph nodes from ground beef is not possible, other approaches should be explored. Easily accessible lymph nodes could be screened for Salmonella very early in the slaughter process. When the results are positive for Salmonella, the corresponding carcasses should be fabricated separately at the end of the production run, and the trim from these carcasses should be subjected to a treatment that destroys Salmonella.
本研究旨在确定碎牛肉中沙门氏菌的污染来源。在美国的一家商业牛肉加工厂，对 100 头奶牛进行了屠宰。采集了牛皮、去皮后的胴体（在进行抗菌干预之前）、所有抗菌干预后的胴体、肩部的浅表颈淋巴结、修整料、碎牛肉和空气样本。96%的牛皮样本、47%的干预前胴体、18%的淋巴结、7.14%的修整料和 1.67%的碎牛肉样本呈沙门氏菌阳性。在进行完所有抗菌干预措施后，从胴体中获得的所有样本以及空气中的样本均未检测到沙门氏菌。所有检测呈阳性的沙门氏菌样本均进行了脉冲场凝胶电泳，共鉴定出 8 种 Xba I 限制酶图谱。多数分离株有两种限制酶图谱之一。从碎牛肉中分离出的菌株与从牛皮和去皮后立即的胴体中分离出的菌株具有相同的图谱。从修整料和淋巴结中分离出的沙门氏菌分离株也具有相同的限制酶图谱。这些结果表明，牛皮和淋巴结是碎牛肉中沙门氏菌的最可能来源。应考虑采取一些措施，如对牛体进行有效处理，降低或消除细菌从牛皮向胴体的转移，以及不将淋巴结作为生碎牛肉的组成部分，以减少碎牛肉中沙门氏菌的污染。由于无法将淋巴结从碎牛肉中完全去除，因此应探索其他方法。可以在屠宰过程的早期非常容易地对易接近的淋巴结进行沙门氏菌筛查。当结果呈沙门氏菌阳性时，应在生产结束时将相应的胴体单独加工，并对这些胴体的修整料进行处理，以消灭沙门氏菌。
