多重耐药伤寒沙门菌耐药基因的研究

An examination of the genes of multi-drug resistant Salmonella typhi

目的检测多重耐药伤寒沙门菌对抗菌药物的敏感性及其耐药基因定位。方法随机选取实验室保存的5株耐药菌和1株敏感菌,用纸片扩散法检测对12种抗菌药物的敏感性。用利舍平抑制试验检测菌株是否存在药物外排系统。用聚合酶链反应(PCR)检测TEM型β内酰胺酶基因、aac(6′)-Ⅰb和aac3-Ⅱ型氨基糖苷类修饰酶基因、qacEΔ1-sul1耐消毒剂和磺胺基因、catA和catB氯霉素乙酰基转移酶基因以及cmlA氯霉素外排泵蛋白基因等7种耐药基因。结果5株多重耐药菌对氨苄西林、哌拉西林、头孢呋辛、头孢西丁、卡那霉素、庆大霉素、复方磺胺甲唑及氯霉素等8种抗菌药物全部耐药,对美罗培南、头孢哌酮、头孢吡肟全部敏感;对头孢噻吩中度敏感。1株无质粒pRST98的菌株对上述药物全部敏感。利舍平抑制试验均为阴性。4株耐药菌TEM型β内酰胺酶基因检测为阳性。全部耐药菌株aac3-Ⅱ、qacEΔ1-sul1和catA基因均为阳性,而aac(6′)-Ⅰb、catB和cmlA基因均为阴性。结论多重耐药伤寒沙门菌质粒pRST98上同时存在多种耐药基因,是导致菌株同时对多种结构各异的抗菌药物耐药的原因。

Objective To identify the antibiotic sensitivity of multi-drug resistant Salmonella typhi and to detect its resistant genes. Methods Five resistant Solmonella typhi strains and 1 sensitive strain were randomly selected. Antibiotic susceptibility to 12 different antibiotics were tested using the K-B method. A reserpine inhibition test was also performed in order to examine the drug excretion system. The TEM type of β-1actamase gene, tuninoglycosides-modifying enzyme gene, aac（6＇）-Ⅰ b, aac3-Ⅱ, qacEAl-sull genes, catA gene, catB gene, and cmlA gene were all detected by PCR. Results Five multi-drug resistant strains were resistant to ampiciUin, piperacillin, cefuroxime, ceftazidime, kanamycin, gentamicin, trimesulf and chloramphenicol, whereas all were sensitive to meropenem, cefoperazone and cefepime and an intermediate sensitivity to cafalotin. The strain which does not carry pRST98 was sensitive to all antibiotics. All strains were negative in the reserpine inhibition test. Five drug-resistant strains carried aac3-Ⅱ , qacEAl-sull and catA genes, 4 carried the TEM type of β-1actamase gene, but none of the 5 strains carried aac（6＇）- Ⅰ b, catB or cmlA genes. Conclusion The multi-drug resistant Salmonella typhi strains that carry pRs19s contained an array of drug resistant genes, leading to the resistance to different antibiotics.