Novel variants of the Smqnr family of quinolone resistance genes and its distribution in clinical isolates of Stenotrophomonas maitophilia / 中华检验医学杂志

ABSTRACT

ObjectiveTo 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 inhibitoryconcentrationsof tigecycline,chloramphenicol,ceftazidime,compoundsulfamethoxazole,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.