Caseous lymphadenitis (CL) in sheep is a chronic contagious disease caused by Corynebacterium pseudotuberculosis, commonly characterized by abscess formation in peripheral lymph nodes and disseminated infections. Nonetheless, other microorganisms, including with zoonotic relevance, can be isolated from CL-resembling lymph nodes. Currently, mycobacteria have been reported in visceral granulomatous lesions in small ruminants, a fact that poses a public health issue, particularly in slaughtered sheep intended for human consumption. Cytology using fine needle aspiration and microbiological culturing are suitable tests for routine diagnostic, whereas present drawbacks and molecular methods have been confirmatory. Data about the occurrence of mycobacteria in both lymph nodes with aspect of CL and apparently healthy visceral nodes of sheep slaughtered for human consumption are scarce. In this study, 197 visceral lymph nodes of sheep showed lymphadenitis and 202 healthy visceral lymph nodes of slaughtered sheep intended for human consumption were submitted to conventional bacteriological diagnosis, mycobacteria culturing, and cytological evaluation. Compatible Corynebacterium isolates were subjected to multiplex PCR targeting 16S rRNA, rpoB, and pld genes to detect C. pseudotuberculosis. Based on microbiological identification, C. pseudotuberculosis (86/197; 43.7%), streptococci γ-hemolytic (17/197; 8.6%), and Trueperella pyogenes (12/197; 6.1%) were prevalent in lymph nodes with abscesses, as opposed to staphylococci (53/202; 26.2%) in apparently healthy lymph nodes. No mycobacteria were isolated. Cytology identified 49.2% (97/197) Gram-positive pleomorphic organisms (coryneform aspect). Multiplex PCR confirmed genetic material of C. pseudotuberculosis in 74.4% (64/86) of the samples with C. pseudotuberculosis isolation and 66% (64/97) samples with cytological coryneform aspect (κ = 86.78%; 95% CI = 79.87-93.68%). These findings emphasize the prevalence of C. pseudotuberculosis in abscess formation among peripheral lymph nodes of sheep. Other bacteria were also identified in lymph nodes sampled that resembling C. pseudotuberculosis-induced infections that may difficult the diagnosis. Multiplex PCR revealed a valuable assay to detect C. pseudotuberculosis, in addition to routine methods applied to CL-diagnosis. No mycobacteria were identified in lymph nodes sampled, with and without apparent lesions. Nonetheless, due to public health impacts, this pathogen should be considered as a differential diagnosis of C. pseudotuberculosis-induced infections during inspection procedures of slaughtered sheep intended for human consumption.

中文翻译：

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假结核棒状杆菌、分枝杆菌和其他细菌在屠宰羊的干酪性淋巴结炎和健康淋巴结中的细菌学、细胞学和分子学研究

绵羊干酪性淋巴结炎（CL）是由假结核棒状杆菌引起的慢性传染性疾病，通常以外周淋巴结形成脓肿和播散性感染为特征。尽管如此，可以从类似 CL 的淋巴结中分离出其他微生物，包括与人畜共患相关的微生物。目前，已经报道了小反刍动物内脏肉芽肿病变中存在分枝杆菌，这一事实构成了公共健康问题，特别是在供人类食用的屠宰羊中。使用细针抽吸和微生物培养的细胞学是常规诊断的合适测试，而目前的缺点和分子方法已得到证实。关于在 CL 方面的淋巴结和为人类屠宰的羊的明显健康的内脏淋巴结中出现分枝杆菌的数据很少。在这项研究中，197 只羊的内脏淋巴结显示淋巴结炎，202 只供人类食用的屠宰羊的健康内脏淋巴结接受常规细菌学诊断、分枝杆菌培养和细胞学评估。对兼容的棒状杆菌分离株进行靶向 16S rRNA、rpoB 和 pld 基因的多重 PCR，以检测假结核杆菌。根据微生物学鉴定，假结核杆菌（86/197；43.7%）、γ-溶血性链球菌（17/197；8.6%）和化脓性真丝菌（12/197；6.1%）在脓肿淋巴结中普遍存在，如反对葡萄球菌 (53/202; 26. 2%) 在明显健康的淋巴结中。没有分离到分枝杆菌。细胞学鉴定了 49.2% (97/197) 革兰氏阳性多形性生物体（棒状体）。多重 PCR 在 74.4% (64/86) 的具有假结核杆菌分离的样本和 66% (64/97) 具有细胞学棒状方面的样本 (κ = 86.78%; 95% CI = 79.87-) 中证实了假结核的遗传物质93.68%）。这些发现强调了在绵羊外周淋巴结形成脓肿中假结核棒状杆菌的流行。在采样的淋巴结中还发现了其他细菌，类似于假结核杆菌引起的感染，可能难以诊断。除了应用于 CL 诊断的常规方法外，多重 PCR 还揭示了一种有价值的检测方法来检测假结核杆菌。在采样的淋巴结中未发现分枝杆菌，有无明显病变。尽管如此，由于对公共健康的影响，在供人类食用的屠宰绵羊的检查程序中，这种病原体应被视为对假结核杆菌引起的感染的鉴别诊断。