肠炎沙门菌临床分离株耐药性与耐药基因分析

Antimicrobial susceptibility test and resistance gene analysis of clinical isolates of Salmonella enteritidis

目的对分离自北京、广州、新疆3个地区腹泻病人粪便标本中的肠炎沙门菌菌株进行耐药性监测,并分析其耐药基因的变异情况。方法应用生化试验、血清凝集试验对分离的疑似沙门菌菌株进行鉴定。采用K-B药敏纸片法对鉴定出的肠炎沙门菌进行抗生素敏感性试验。利用PCR技术扩增其耐药基因DNA促旋酶gyrA基因和拓扑异构酶parC基因,同时进行测序。结果共分离鉴定出20株肠炎沙门菌,分离菌株对环丙沙星、庆大霉素、头孢他定、亚胺培南的敏感率为100%,对萘啶酸耐药;75%的菌株呈现多重耐药性(multidrug resistance,MDR)序列比对结果显示gyrA基因Asp87及Gly133密码子处发生了点突变,其中Gly133是新的突变点。未发现parC基因密码子突变。结论肠炎沙门菌临床分离株MDR情况比较严重,对萘啶酸普遍耐药,这可能与20株菌的gyrA基因QRDR的突变相关。为防止多重耐药现象的蔓延和加重,除了应加强耐药性及耐药性相关基因的实验室监测外,临床治疗沙门菌感染时需慎用抗生素。

Objective To analyze drug resistance and the mutations of resistance genes of Salmonella enteritidis isolated from diarrhea patients in China.Methods The suspected strains were identified with conventional biochemical test and serum agglutination test.Antibiotic susceptibility test was performed according to K-B methods.The DNA gyrase A and topoisomerase IV parC genes were amplified by PCR technique,and the amplified products were sequenced.Results Totally 20 Salmonella enteritidis strains were identified.All of the strains were sensitive to ciprofloxacin,gentamycin,ceftazidime and imipenem,and resistant to nalidixic acid.Of all strains,75% presented multi-drug resistance（MDR）.Nucleotide sequence analysis showed that all of the strains had mutations in codons Asp87 and Gly133 in quinolone resistance-determining region（QRDR） of gyrA gene,while the Gly133 point mutation was novel.Mutation was not found in parC gene.Conclusion The results showed severe multi-drug resistance of clinically-isolated strains of Salmenella enteritidis,and nalidix acid resistance is common.This is probably attributable to point mutations in QRDR of gyrA gene.The antibiotics should be prudently used for the treatment of Salmonella infections.