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目的研究耐药基因ermB、mefA、tetM与转座子整合酶基因intTn在携带肺炎链球菌的北京儿童中分布特点。方法对185株呼吸道感染患儿鼻咽部分离的肺炎链球菌进行以下检测:Etest、琼脂稀释或纸片扩散法测定对大环内酯类、四环素、β内酰胺类及头孢类等15种抗生素的药物敏感性。PCR检测大环内酯类耐药基因ermB和mefA,四环素耐药基因tetM以及转座子Tn1545的整合酶基因intTn。结果185株肺炎链球菌的药敏结果显示,对红霉素、克林霉素、四环素和复方磺胺甲基异唑的耐药率较高,分别为78.9%、76.2%、86.0%和78.7%,对阿莫西林克拉维酸、头孢克洛、头孢曲松和头孢呋辛耐药率较低,分别为2.2%、15.5%、2.8%和14.1%。所有红霉素耐药株均检出ermB和或mefA,其中79.5%为ermB阳性,17.8%为ermB和mefA同时阳性,2.7%为mefA阳性。tetM基因在分离株中的阳性率是87%,四环素耐药组的tetM基因携带率是96.9%,高于敏感组(26.9%)。四环素耐药株的红霉素耐药率(90.0%)亦高于敏感株组(11.5%)。87.6%的肺炎链球菌存在intTn基因,intTn基因阳性组的红霉素、四环素、氯霉素、复方磺胺甲基异唑和环丙沙星的耐药率较intTn基因阴性组高。分离株最常见的基因组合是intTn+tetM+ermB,占58.4%。结论北京地区呼吸道感染儿童鼻咽部肺炎链球菌耐大环内酯类抗生素的主要原因是ermB编码的23SrRNA甲基化酶致靶位改变。tetM基因编码蛋白质的核糖体保护作用,是肺炎链球菌四环素耐药的重要机制。接合性转座子Tn1545的存在与菌株的红霉素和四环素耐药关系密切,可能是肺炎链球菌多重耐药的重要机制之一。
Objective To study the distribution of resistance genes ermB, mefA, tetM and transposon integrase gene intTn in Beijing children carrying Streptococcus pneumoniae. Methods 185 isolates of respiratory tract infection in children with nasopharyngeal pneumonia isolated from the following tests: Etest, agar dilution or disk diffusion method for macrolide, tetracycline, β-lactams and cephalosporins and other 15 kinds of antibiotics The drug sensitivity. PCR detection of macrolide resistance genes ermB and mefA, tetracycline resistance gene tetM and transposon Tn1545 integrase gene intTn. Results The susceptibility results of 185 strains of S. pneumoniae showed that the resistance rates to erythromycin, clindamycin, tetracycline and sulfamethoxazole were higher, being 78.9%, 76.2%, 86.0% and 78.7, respectively %. The rates of resistance to amoxicillin and clavulanic acid, cefaclor, ceftriaxone and cefuroxime were low, which were 2.2%, 15.5%, 2.8% and 14.1% respectively. All erythromycin resistant strains were positive for ermB and / or mefA, with 79.5% positive for ermB, 17.8% positive for both ermB and mefA, and mefA positive 2.7%. The positive rate of tetM gene in isolates was 87%. The tetM gene resistance rate in tetracycline resistant group was 96.9%, higher than that in sensitive group (26.9%). The erythromycin resistance rate of tetracycline resistant strains (90.0%) was also higher than that of susceptible strains (11.5%). The intTn gene was found in 87.6% of S. pneumoniae strains. The drug resistance rates of erythromycin, tetracycline, chloramphenicol, sulfamethoxazole and ciprofloxacin in intTn positive group were higher than those in intTn negative group. The most common gene combination of isolates was intTn + tetM + ermB, accounting for 58.4%. Conclusion The main reason of resistance to macrolide antibiotics of nasopharyngeal pneumonia in children with respiratory tract infection in Beijing is that the target site of 23SrRNA methylase encoded by ermB is changed. TetM gene encoding protein ribosome protection, is an important mechanism of tetracycline resistance in Streptococcus pneumoniae. The presence of the junctional transposon Tn1545 is closely related to erythromycin and tetracycline resistance of the strain, which may be one of the important mechanisms of multi-drug resistance of Streptococcus pneumoniae.