嗜麦芽窄食单胞菌新型突变喹诺酮耐药基因Smqnr及其分布

目的 描述新型突变喹诺酮耐药基因Smqnr及其在嗜麦芽窄食单胞菌的分布，初步探讨Smqnr基因与喹诺酮抗生素耐药之间的关系。方法 嗜麦芽窄食单胞菌的鉴定采用VITEK全自动细菌鉴定和药敏系统，采用标准琼脂稀释法测定替加环素、氯霉素、头孢他啶、复方磺胺甲(恶)唑、替卡西林/克拉维酸、左氧氟沙星、莫西沙星7种抗生素对442株嗜麦芽窄食单胞菌的最低抑菌浓度(MIC)。聚合酶链反应(PCR)扩增全长Smqnr基因，测序后采用DNAMAN软件比对序列之间的差异，并构建系谱树分析不同Smqnr基因之间亲缘性关系。结果 嗜麦芽窄食单胞菌对7种抗菌药物有不同程度的耐药，且在5％ ～50％之间变动，左氧氟沙星的抗菌活性较好，耐药率仅为6.11％ (27/442)，抗菌活性最好的药物为莫西沙星，耐药率为5.88％( 25/442)，442株嗜麦芽窄食单胞菌中114株检测到Smqnr基因，检出率为25.79％ (114/442)，包括11种已发现的Smqnr和20种新型突变的Smqnr基因（Smqnr 28 ～ 47），新型突变的Smqnr基因是由于部分碱基发生突变导致相应的219位翻译氨基酸位点发生改变。耐药株Smqnr基因检出率为42.30％ (11/26)，中介株Smqnr基因检出率为34.37％( 11/32),敏感株检出率23.95％ (92/384)，敏感株中MIC为0.125 μg/ml的嗜麦芽窄食单胞菌Smqnr基因检出率最高，为37.78％。结论Smqnr基因编码区高度多态，新型突变的Smqnr基因是由于部分碱基发生突变导致相应的219位翻译氨基酸位点发生改变所致。Smqnr基因在嗜麦芽窄食假单胞菌中的检出率较高，分布也存在较大差异。

Novel variants of the Smqnr family of quinolone resistance genes and its distribution in clinical isolates of Stenotrophomonas maitophilia

Objective To describe the novel variants of the Smqnr family of quinolone resistance genes and their distribution in clinical isolates of Stenotrophomonas maltophilia, and investigate the relationship between Smqnr and quinolone resistance. MethodsThe identification of 442 strains of Stenotrophomonas maltophilia were performed by VITEK automated identification and susceptibility. Minimum inhibitory concentrations of tigecycline, chloramphenicol, ceftazidime, compound sulfamethoxazole,ticarcillin/clavulanic acid, levofloxacin and moxifloxacin against Stenotrophomonas maltophilia were detected by standard agar dilution method. Full length of Smqnr gene was amplified by polymerase chain reaction (PCR) and sequenced. DNAMAN software was used to compare the sequence divergence and construct the genealogical tree to analyze the phylogenetic relationships of Smqnr family. Results Stenotrophomonas maltophilia was resistant to the 7 kinds of clinical antibiotics in various extent ( from 5％ to 50％ ). Levofloxacin showed s good antibacterial activity with the resistance rate of 6. 11％ (27/442), nevertheless the best was moxifloxacin with the resistance rate of 5. 88％ (25/442). Smqnr gene was detected in 114 of 442 strains of Stenotrophomonas maltophilia[25.79％ (114/442)], including 11 known genes and 20 novel variants of the Smqnr genes ( Smqnr28-47 ) which was caused by several genes mutation changing the translation of 219 amino acids. The gene detection rate of resistant, intermediate and sensitive strains was 42. 30％ (11/26), 34. 37％ (11/32) and 23.95％ (92/384), respectively. The Smqnr gene harbored the highest detection rote (37. 78％ ) in the sensitive strains of Stenotrophomonas maltophilia with minimal inhibitory concentration of 0. 125 μg/ml. Conclusions The gene coding region of Smqnr is highly polymorphic and the novel variants of Smqnr gene are caused by several genes mutation changing the translation of 219 amino acids. Smqnr gene in Stenotrophomonas maltophilia has a high detection rate and different distribution.