42株形成生物被膜的嗜麦芽窄食单胞菌的药物敏感性研究

In vitro susceptibility assay of 42 Stenotrophomonas maltophUia with biofilms to antibiotic agents

目的研究单独及联合使用不同种类抗生素对嗜麦芽窄食单胞菌（Stenotrophomonas maltophilia，SML）体外生物被膜的抗菌活性。方法收集从患者分离的非重复SML42株，分别采用微量接种针和硅胶膜片在水解酪蛋白肉汤中构建细菌生物被膜（bacterial biofilm）的体外模型，经过抗生素（左氧氟沙星、环丙沙星、头孢哌酮／舒巴坦、头孢他啶、哌拉西林、红霉素、磺胺甲嗯唑、庆大霉素）作用20h，超声振荡并测定孵育前后6h吸光度（A）值的变化，计算相应的细菌生物被膜抑制浓度，进而测定红霉素与左氧氟沙星、头孢哌酮／舒巴坦、哌拉西林对细菌生物被膜的联合作用。结果SML对左氧氟沙星、磺胺甲嗯唑和哌拉西林敏感率分别为83．33％、66．67％和54．76％，其他抗生素的耐药率均在50％以上。形成生物被膜后，细菌对抗生素的生物被膜抑制浓度大于相应的最小抑菌浓度（MIC）值。结论42株SML呈现多重耐药现象，形成生物被膜后耐药性增强。左氧氟沙星的抗菌活性在形成生物被膜前后均优于其他抗生素，联合红霉素与左氧氟沙星有助于增强杀菌效果。

Objective To investigate the effects of levofloxacin, ciprofloxacin, ceftazidime, pip- eracillin, cefoperazone/sulbactam, erythromycin, sulfamethoxazole and gentamycin on the bacterial biofilms of Stenotrophomonas maltophilia. Methods Biofilm and conventional susceptibilities were determined for S. maltophilia isolates from 42 patients. The model of S. maltophilia biofilms in vitro was developed in the Mueller-Hinton broth--microtiter inoculator or silica films. After antibiotic challenge plate 20 h, each plate was sonicated and the absorbance value at 620 nm（A620 ） was measured on a microtiter plate colorimeter before and after incubation for 6 h. Then the biofilm inhibitory concentrations were calculated. Finally, based on the acquired data, the experiments of combination effects of erythromycin with the 3 antibiotic agents on the formed biofilms of 5 picked strains were designed and worked ont. Results The sensitive rate of 42 S. maltophilia to levofloxacin, sulfamethoxazole and piperacillin were 83.33%, 66.67% and 54.76%, respectively. The bilfilm inhibitory concentrations were much higher than the corresponding minimal inhibitory concentrateion after formed biofilms. Conclusion Forty-two S. maltophilia are multi-resistant to antibiotic agent. And levofloxacin may have a better effect against biofilms compared with others. The inhibition effect of combination erythromycin with levofloxacin is more obvious among all the 3 antibiotic agents.