鸡源mcr-1阳性多重耐药沙门菌的鉴定和特征分析

Identification and Characteristic Analysis of mcr-1 Positive Multidrug Resistant Salmonella in Chicken

试验旨在对1株鸡源mcr-1阳性多重耐药沙门菌株进行鉴定以及特征分析,从河南鸡场采集病死鸡样品总计187份,通过SS选择培养基进行沙门菌的分离,利用聚合酶链式反应(PCR)方法扩增16S rRNA和invA对菌株进行鉴定,基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)复核鉴定结果,并采用PCR测序的方法检测黏菌素耐药基因mcr的携带情况。采用微量稀释法测定沙门菌对常见16种抗菌药的敏感性,通过全基因组测序分析沙门菌的特征。结果显示,共分离鉴定出32株鸡源沙门菌,分离率为17.11%,黏菌素耐药率为18.75%;在1株沙门菌中检测到了黏菌素耐药基因mcr-1,检出率为3.13%。mcr-1阳性鸡源沙门菌的黏菌素最小抑菌浓度为16μg/mL,多序列位点分型结果为ST9。药敏结果显示,该菌株对氨苄西林、头孢噻呋、庆大霉素、大观霉素、恩诺沙星、环丙沙星、氟苯尼考、氯霉素、磺胺异恶唑、甲氧嘧啶、四环素耐药;携带blaOXA-1、blaTEM-1B、oqxAB、tet(A)、floR、catB3、sul1、sul2、sul3、ant(3'')、dfrA等多种耐药基因。接合试验证实mcr-1基因可发生接合转移。该研究结果为临床治疗鸡源沙门菌感染中合理使用抗生素以及有效预防、控制耐黏菌素鸡源沙门菌的传播提供了科学依据。

The aim of the study was to identify and analyze the characteristics of a chicken derived mcr-1 positive multidrug-resistant Salmonella strain.A total of 187 samples of dead chicken were collected from a chicken farm in Henan.Salmonella isolation was performed using SS selective medium,and the strains were identified by amplifying 16S rRNA and invA genes through polymerase chain reaction(PCR).MALDI-TOF-MS was used for confirmation,and the presence of the colistin resistance gene mcr was detected by PCR sequencing.The sensitivity of Salmonella strains to 16 common antibiotics was determined using the microdilution method,and the characteristics of the Salmonella strains were analyzed through whole genome sequencing.Results showed a total of 32 Salmonella strains in chicken were isolated and identified,with an isolation rate of 17.11%.The colistin resistance rate of these strains was 18.75%,and the colistin resistance gene mcr-1 was detected in 1 strain of Salmonella,resulting in a detection rate of 3.13%.The minimum inhibitory concentration of colistin for the mcr-1 positive chicken-origin Salmonella was 16μg/mL,and the multilocus sequence typing revealed ST9 as the sequence type.Antimicrobial susceptibility testing showed resistance of this strain to ampicillin,cefotaxime,gentamicin,spectinomycin,enrofloxacin,ciprofloxacin,flufenicol,chloramphenicol,sulfamethoxazole,oxydiazine and tetracycline.The strain carried various resistance genes such as blaOXA-1,blaTEM-1B,oqxAB,tet(A),floR,catB3,sul1,sul2,sul3,ant(3'')and dfrA.Conjugation experiments confirmed that the mcr-1 gene can undergo conjugation transfer.The research results provide a scientific basis for the rational use of antibiotics in clinical treatment of Salmonella infections in chicken and effective prevention and control of the spread of colistin-resistant Salmonella in chicken.