Abstract：
Salmonella enterica is considered a significant threat to the global poultry industry and public health. In recent decades, antimicrobial resistance in Salmonella enterica has attracted increasing concern throughout the world. However, limited information is available on Salmonella enterica among different breeds of breeder chickens. Thus, this study aimed to compare the prevalence, serotype distribution, emergence of extended-spectrum beta-lactamases (ESBLs), antimicrobial resistance, and genetic resistance mechanisms in Salmonella enterica among different breeds of breeder chickens. A total of 693 samples (dead embryos, cloacal swabs, water, feed, environmental swabs, and meconium of newly hatched chicks) were selected and cultured for Salmonella from four breeder chicken farms in Shandong province, China, representing one imported and three native breeds, and the isolates were further serotyped. Of the Salmonella isolates, susceptibility to 11 antimicrobials of 5 classes, ESBL screening, and the presence of 21 antimicrobial resistance genes were determined in the present study. Overall, 94 (13.6%) isolates were recovered, which were divided into 3 serotypes (Salmonella Pullorum (n = 36), Salmonella Thompson (n = 32), and Salmonella Enteritidis (n = 26)). The results showed that the prevalence of Salmonella enterica isolates from the imported breeds was higher compared with the three domestic breeds. Eight of the ninety-four isolates were ESBL-positive strains, which were recovered from a domestic breed chicken farm. These eight ESBL-producing isolates were serotyped to Pullorum. Surprisingly, Salmonella Enteritidis (S. enteritidis) and S. pullorum were simultaneously isolated from a single dead embryo observed among one native breed. Meanwhile, among the Salmonella isolates, 53.2% (50/94) were multidrug-resistant strains, and 44.7% (42/94) of the isolates presented resistance to at least five antibiotics. Nearly all of the isolates (97.9%, 92/94) were resistant to at least one antimicrobial; one isolate of S. Thompson was resistant to seven antimicrobial agents belonging to four different classes. The carriage rate of three resistance genes (tetA, tetB, and sul1) among isolates from the imported breeds (87%, 70%, and 65.2%) was higher than that in those from domestic breeds (35.2%, 36.6, and 14.1%). To our knowledge, this is the first report of ESBLs-producing Salmonella isolated from a Chinese native breed of breeder chickens. Our results also highlight that a high prevalence of multidrug-resistant Salmonella enterica contamination is widespread among different breeds of breeder chickens, which is a major risk of food-borne diseases and public health.
摘要：
肠沙门氏菌被认为是对全球家禽业和公共卫生的重大威胁。近几十年来,肠道沙门氏菌的耐药性已引起全世界越来越多的关注。然而,关于不同种鸡品种的肠道沙门氏菌的信息有限。因此，这项研究旨在比较患病率，血清型分布,超广谱β-内酰胺酶（ESBLs）的出现，抗菌素耐药性，以及不同品种种鸡中沙门氏菌的遗传抗性机制。总共693个样本(死亡胚胎，泄殖腔拭子,水,饲料，环境拭子,和新孵化雏鸡的胎粪）从山东省四个种鸡场中选择并培养沙门氏菌，中国,代表一个进口品种和三个本地品种，并对分离株进行进一步的血清分型。沙门氏菌分离株中，对5类11种抗菌药物的敏感性，ESBL筛查,本研究确定了21种抗菌药物耐药基因的存在。总的来说,回收94株(13.6%),分为3种血清型（鸡沙门氏菌（n=36），汤普森沙门氏菌（n=32），和肠炎沙门氏菌（n=26））。结果表明，与三个国内品种相比，进口品种的沙门氏菌流行率较高。94株分离株中有8株是ESBL阳性菌株，是从一个国内品种养鸡场回收的。将这8个产生ESBL的分离株血清分型为Pulloum。令人惊讶的是,肠炎沙门氏菌（S.从一个本地品种中观察到的单个死胚胎中同时分离出肠炎）和鸡白鼠。同时,在沙门氏菌分离物中，53.2%(50/94)为多重耐药菌株，44.7%(42/94)的分离株对至少5种抗生素存在耐药性。几乎所有的分离株（97.9%，92/94）对至少一种抗微生物剂具有抗性；S.Thompson的一种分离株对属于四种不同类别的七种抗微生物剂具有抗性。三个抗性基因(tetA，tetB,和sul1)在来自进口品种的分离株中(87%，70%,和65.2%)高于国内品种(35.2%，36.6和14.1%）。据我们所知,这是从中国本土种鸡中分离出的产ESBLs沙门氏菌的首次报道。我们的研究结果还强调，多重耐药沙门氏菌肠道污染的高患病率在不同品种的种鸡中普遍存在，这是食源性疾病和公共卫生的主要风险。
