鹌鹑源鼠伤寒沙门氏菌的分离鉴定与耐药性分析

Isolation, identification, and drug resistance analysis of Salmonella Typhimurium from quails

摘要:

【背景】在鹌鹑养殖过程中，抗菌药物和消毒剂的不规范使用加剧了耐药菌株在动物、场所和食品之间的相互传播，因此，掌握致病菌株在养殖动物中的耐药状况至关重要。【目的】检测北京周边地区鹌鹑蛋源致病菌株的耐药特征和耐药基因的流行情况。【方法】在天津市武清区部分鹌鹑养殖场采集鹌鹑泄殖腔粪便、鹌鹑蛋表、养殖环境和鹌鹑饮水的样品，通过细菌分离培养、菌落形态观察、染色镜检、生化鉴定、血清分型、沙门氏菌invA基因序列测定等方法对分离菌株进行鉴定。同时进行小鼠攻毒试验，测定小鼠半数致死量（median lethal dose，LD₅₀）。再通过药敏试验和PCR方法对分离菌的耐药表型、耐药基因及毒力基因进行检测。【结果】分离菌株菌落颜色、镜检形态和生化试验结果符合沙门氏菌特性，沙门氏菌invA基因序列测定与鼠伤寒沙门氏菌参考株相似度为99.44%，鉴定为鼠伤寒沙门氏菌，血清型为1，4，[5]，[12]：i：l，2。该菌株对小鼠有致病作用，小鼠LD₅₀为2.10×10⁷ CFU/mL；药敏试验结果显示该菌株对氨苄西林、阿莫西林/克拉维酸、头孢噻呋、链霉素、磺胺甲啞唑、磺胺异啞唑、诺氟沙星、环丙沙星表现耐药，对头孢唑林等10种抗菌药物敏感；对阳离子表面活性剂和过氧化物类消毒剂的抗性增加；菌株携带bla_TEM等4种耐药基因及mogA等13种毒力基因。【结论】从鹌鹑养殖场分离得到一株致病性鼠伤寒沙门氏菌，具有多重耐药特性并携带多种毒力基因。试验结果为鹌鹑源沙门氏菌的危害评估和防控措施制定提供了参考。

Abstract:

[Background] The irregular use of antimicrobials and disinfectants in quail breeding has exacerbated the spread of drug-resistant strains between animals, premises, and food. So it is important to understand the drug-resistant status of pathogenic strains of farmed animals. [Objective] To detect the drug resistance characteristics and the prevalence of drug resistance genes in the pathogenic strains derived from quail eggs in the quail farms around Beijing. [Methods] The samples of quail cloacal feces, quail egg surface, breeding environment, and quail drinking water were collected from some quail farms in Wuqing District, Tianjin. A strain was isolated and identified by colony morphology observation, staining microscopy, and biochemical tests. Serotyping and invA sequencing were carried out for this strain. Furthermore, the mouse challenge test was performed to determine the median lethal dose (LD₅₀), and the drug susceptibility test and PCR were employed to detect the drug resistance phenotypes and genes and the virulence genes of the isolates. [Results] The colony color, microscopic morphology, and biochemical properties of the isolates were consistent with those of Salmonella. The invA sequencing results showed that the strain had 99.44% homology with the reference strain of Salmonella Typhimurium, and thus it was identified as S. Typhimurium, with the serotype being 1,4,[5],[12]:i:l,2. The strain had pathogenic effect on mouse, with the LD₅₀ of 2.10×10⁷ CFU/mL. It was resistant to ampicillin, amoxicillin/clavulanate, ceftiofur, streptomycin, sulfamethoxazole, sulfafurazole, norfloxacin, and ciprofloxacin and sensitive to ten antibiotics such as cefazolin. The strain presented enhanced resistance to cationic surfactants and peroxide disinfectants. It carried four resistance genes such as bla_TEM and thirteen virulence genes such as mogA. [Conclusion] A pathogenic Salmonella Typhimurium strain was isolated from a quail farm. It has multi-drug resistance and carries multiple virulence genes. The results provide a reference not only for the hazard assessment but also for the formulation of prevention and control measures of Salmonella from quails.