Salmonellosis is one of the main foodborne diseases worldwide. Breeding sows asymptomatically infected with Salmonella can transmit the pathogen to piglets and humans. The isolation of Salmonella from mesenteric lymph nodes (MLNs) is considered a demonstration of asymptomatic infection in swine. As previous breeding sow studies have been performed using feces, the aim of this work was to study the occurrence of Salmonella infections by sampling MLNs, in comparison to their serological status. First, Salmonella fecal shedding was studied in 12/16 large breeding farms to establish the framework of study. Then, MLN (n = 264) and blood (n = 237) samples were obtained at an abattoir from sows of 15 of these 16 breeding farms. Additionally, risk factors associated with Salmonella MLN infection were analyzed. A total of 6.1% (16/264) sows, distributed in 40% (6/15) of the farms, had the pathogen in MLN. Salmonella Typhimurium was the most frequent serovar isolated. Interestingly, 43.8% (7/16) of MLN isolates were susceptible to all the antimicrobials tested and were found distributed throughout all farms with at least one sow positive. As well, one isolate of the emerging DT195 clone was detected and found to be resistant to six antibiotic families (ASSuTNx-Cfx). The serovars and the resistance profiles of the Salmonella isolates from feces were completely different to those obtained from MLNs. The seroprevalence (41.8% of sows and 100% of farms) was higher than that of MLN infections, showing no concordance (k = 0.15) between these two diagnostic tests in sows. Strategies directed to correct two risk factors (i.e., administration of dry food and old premises) would most likely help to reduce Salmonella infections in breeding sows.

中文翻译：

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繁殖母猪肠系膜淋巴结中的沙门氏菌感染。

沙门氏菌病是全球主要的食源性疾病之一。无症状感染沙门氏菌的繁殖母猪可以将病原体传播给仔猪和人类。从肠系膜淋巴结（MLN）分离沙门氏菌被认为是猪无症状感染的例证。由于以前使用粪便进行了繁殖母猪研究，因此这项工作的目的是通过对MLN的血清学状况进行比较来研究沙门氏菌感染的发生。首先，在12/16大型繁殖场中对沙门氏菌粪便脱落进行了研究，以建立研究框架。然后，MLN（n  = 264）和血液（n = 237）在这16个繁殖场中的15个繁殖场的母猪的屠宰场获得了样本。此外，分析了沙门氏菌MLN感染相关的危险因素。分布在40％（6/15）的农场中，共有6.1％（16/264）母猪在MLN中有病原体。鼠伤寒沙门氏菌是最常见的血清型。有趣的是，有43.8％（7/16）的MLN分离物易受所有测试的抗生素的影响，发现分布在所有农场中，其中至少有一个母猪呈阳性。同样，还检测到一种新出现的DT195克隆的分离株，发现对六个抗生素家族（ASSuTNx-Cfx）有抗性。沙门氏菌的血清型和耐药性粪便分离株与MLNs完全不同。血清阳性率（41.8％的母猪和100％的农场）高于MLN感染， 这两种母猪的诊断测试之间没有一致性（k = 0.15）。纠正两个危险因素的策略（即管理干粮和旧房舍）最有可能帮助减少繁殖母猪的沙门氏菌感染。