Global dissemination of non-typhoidal Salmonella producing extended-spectrum β-lactamase (ESBL) is a public-health concern. Recently, the prevalence of Salmonella spp. resistant to third-generation cephalosporins has been increasing in food-producing animals in Korea. In this study, we investigated resistance mechanisms and molecular characteristics of S. Virchow isolates resistant to extended-spectrum cephalosporins (ESCs). We obtained 265 S. Virchow isolates from fecal and carcasses samples of cattle (n = 2), pigs (n = 7), and chickens (n = 256) during 2010-2017, and observed high ESC-resistance (63.8%, 169/265); most of the resistant isolates (96.4%) were obtained from chickens. ESC-resistant S. Virchow isolates (n = 169) showed significantly higher resistance rates to other antimicrobials (especially aminoglycosides and tetracycline, p-value <0.0001), as well as prevalence of multidrug resistance, than did ESC-susceptible S. Virchow isolates (n = 96). All ESC-resistant S. Virchow produced CTX-M-15-type ESBL (n = 147) and/or CMY-2-type AmpC β-lactamase (n = 23). ESC-resistant S. Virchow represented seven pulsotypes, predominantly composed of type II (58.6%) and III (26.0%), detected in 69 farms in 10 provinces, and 33 farms in 7 provinces, respectively. Genes encoding ESC-resistance were horizontally transferred by conjugation to recipient E. coli J53; this was demonstrated in 28.8% (42/146) of blaCTX-M-15-positive isolates and in 50.0% (11/22) of blaCMY-2-positive isolates. All conjugative plasmids carrying blaCTX-M-15 and blaCMY-2 genes belonged to ST2-IncHI2 and ST12/CC12-IncI1, respectively. Genetic features of transferred bla genes were involved with ISEcp1 in both blaCTX-M-15 and blaCMY-2; ISEcp1 plays a critical role in the efficient capture, expression, and mobilization of bla genes. In addition to blaCTX-M-15 genes, resistance markers to aminoglycosides and/or tetracycline were co-transferred to recipient E. coli J53. Our results show a high prevalence of ESBL-producing S. Virchow in chickens and chicken carcasses. Specific blaCTX-M-15 and blaCMY-2-carrying S. Virchow clones and plasmids were predominant in food-producing animals nationwide. Restriction of antimicrobial use and proper biosecurity practices at the farm level should be urgently implemented in the poultry industry.

中文翻译：

---

从2010-2017年在韩国从产食动物中分离出的产广谱β-内酰胺酶/ AmpC肠炎沙门氏菌Virchow的分子特征。

产生广谱β-内酰胺酶（ESBL）的非伤寒沙门氏菌的全球传播是一个公共卫生问题。最近，沙门氏菌的流行。在韩国，食用动物对第三代头孢菌素的耐药性一直在增加。在这项研究中，我们调查了S. Virchow分离株对广谱头孢菌素（ESCs）的耐药机制和分子特征。我们在2010-2017年期间从牛（n = 2），猪（n = 7）和鸡（n = 256）的粪便和尸体样品中获得了265株维尔氏分离株，并观察到了高的ESC抗性（63.8％，169） / 265）；大多数抗性分离株（96.4％）来自鸡。耐ESC的S.Virchow分离株（n = 169）对其他抗生素（尤其是氨基糖苷和四环素，p值<0.0001）以及多药耐药的发生率，比ESC易感的S. Virchow分离株（n = 96）。所有抗ESC的葡萄球菌均产生CTX-M-15型ESBL（n = 147）和/或CMY-2型AmpCβ-内酰胺酶（n = 23）。抗ESC的S. Virchow代表7种脉冲型，主要由II型（58.6％）和III型（26.0％）组成，分别在10个省的69个农场和7个省的33个农场中检测到。编码ESC抗性的基因通过缀合水平转移到受体大肠杆菌J53中。blaCTX-M-15阳性分离株的28.8％（42/146）和blaCMY-2阳性分离株的50.0％（11/22）证明了这一点。携带blaCTX-M-15和blaCMY-2基因的所有结合质粒分别属于ST2-IncHI2和ST12 / CC12-IncI1。在blaCTX-M-15和blaCMY-2中，转移的bla基因的遗传特征均与ISEcp1有关。ISEcp1在bla基因的有效捕获，表达和动员中起关键作用。除blaCTX-M-15基因外，对氨基糖苷和/或四环素的抗性标记也共转移到受体大肠杆菌J53中。我们的结果表明，在鸡和鸡尸体中高产ESBL的S. Virchow。特定的blaCTX-M-15和blaCMY-2携带S.Virchow克隆和质粒在全国范围内的食品生产动物中占主导地位。家禽业应紧急实施限制使用抗菌药物和在农场一级采取适当的生物安全措施的措施。对氨基糖苷和/或四环素的抗性标记被共转移至受体大肠杆菌J53。我们的结果表明，在鸡和鸡尸体中高产ESBL的S. Virchow。特定的blaCTX-M-15和blaCMY-2携带S.Virchow克隆和质粒在全国范围内的食品生产动物中占主导地位。家禽业应紧急实施限制使用抗菌药物和在农场一级采取适当的生物安全措施的措施。对氨基糖苷和/或四环素的抗性标记被共转移至受体大肠杆菌J53。我们的结果表明，在鸡和鸡尸体中高产ESBL的S. Virchow。特定的blaCTX-M-15和blaCMY-2携带S.Virchow克隆和质粒在全国范围内的食品生产动物中占主导地位。家禽业应紧急实施限制抗菌药物使用和适当的生物安全措施的农场。