红霉素及左氧沙星单用和联合时抗解脲脲原体MIC的影响

In vitro effect of erythromycin and levofloxacin alone or in combination against ureaplasma urealyticum

目的:研究红霉素及左氧沙星联合应用时抗解脲脲原体临床株最小抑菌浓度(MIC)的影响。方法:用微量液体倍比稀释法及平板棋盘法分别测定单药及联合时对解脲脲原体(Uu)的MIC,并进行FIC计算及统计分析。设定红霉素及左氧沙星的MIC≥8mg.L-1为耐药。结果:共51株标本。联合应用后,红霉素耐药株MIC降低(P<0.05),而敏感株升高(P<0.05);而左氧沙星无论是耐药株还是敏感株的MIC均为降低(P<0.05),耐药株更明显。对红霉素及左氧沙星同时敏感的菌株,联合后红霉素的MIC升高(P<0.05)。在红霉素耐药株及左氧沙星耐药株中,联合后结果为拮抗的比敏感株明显减少。结论:左氧沙星与红霉素联合,有助于降低左氧沙星的MIC及红霉素耐药株对红霉素的MIC,逆转红霉素耐药株对红霉素的耐药性,但也可能增强红霉素敏感株对红霉素的耐药性。

OBJECTIVE To evaluate the effect of erythromycin and levofloxacin alone or in combination against ureaplasma urealyticurru METHODS Multiple-proportional broth microdilution method for erythromycin and levofoxacin alone and checkerboard titration methods for them in combination were applied to detect the MICs against ureaplasma urealyticum. The resuhs were evaluated with both fractional inhibitory concentration index and Ridit analysis. The resistant concentratxon tor both erythromycin and levofloxacin was set MIC≥8 mg· L^- 1. RESULTS 51 clinical strains were enrolled in the study. After combination, the MICs of erythromycin-resistant strains were decreased （P〈0.05） while that of the sensitive strains increased （P〈0. 05）, whereas the MICs of levofloxacin either sensitive or resistant strains were decreased （P〈0. 05）. Furthermore, the MICs of levofloxacin--resistant strains decreased more evidently tban that of sensitive strains. The MICs of erythromycin were raised in the strains which were sensitive to both erythromycin and levofloxacin after combination （P〈0. 05）. The antagonistic ratio in the strains resistant to either erythromycin or levofloxacin were fewer than that of sensitive strains, respectively. CONCLUSION The combination of erythromycin and levofloxacin is helpful to decrease the MICs of levofloxacin against ureaplasma urealyticum and that of erythromycin against erythromycin-resistant strains as well. The combination may reverse the resistance of the erythromycin-resistant strains, but may increase the resistance to erythrornycin on the erythromycin-ensitive strains. However, the findings may suggest avenues of research into new treatment strategies employing antimicrobial combinations with improved selection against resistance, if possible.