亚抑制浓度鱼腥草素钠和红霉素体外诱导对肺炎链球菌耐药性影响

Effects of sodium houttuynia at subinhibitory concentrations and erythromycin induced in vitro on drug resistance of Streptococcus pneumoniae

目的观察亚抑制浓度鱼腥草素钠和红霉素体外诱导对肺炎链球菌(Streptococcus pneumoniae,Sp)耐药性影响,探讨Sp红霉素耐药的分子机制。方法琼脂稀释法测定ATCC6306和10株红霉素敏感临床分离株对鱼腥草素钠和红霉素MICs;1/2MIC的鱼腥草素钠和红霉素为起始浓度进行连续诱导,检测诱导前后菌株对鱼腥草素钠和红霉素的MICs;PCR扩增药物诱导前后菌株L4和L22编码基因rplD和rplV并测序,比较诱导前后氨基酸序列的变化。结果Sp经鱼腥草素钠诱导传代的各临床菌株MICs改变不超过2倍,无耐药株产生;诱导前所有菌株对红霉素的MIC为0.125μg/ml~0.25μg/ml,诱导后ATCC6306和5株临床菌株成为红霉素耐药株,MIC为4μg/ml~32μg/ml,其中ATCC6306和3株临床L4和L22氨基酸序列存在1处~3处替换突变。结论红霉素体外诱导肺炎链球菌获得稳定性耐药,耐药机制可能与核糖体蛋白L4和L22氨基酸突变相关。相对于化学合成药物肺炎链球菌对鱼腥草素钠不易产生耐药。

Objective To investigate the molecular mechanisms of erythromycin resistance in S.pneumonia(Sp),and observe the effect of sodium houttuynia at subinhibitory concentrations and erythromycin induced in vitro on drug resistance of Sp.Methods ATCC6306 and 10 clinical isolates susceptible to erythromycin were determined by AGAR dilution to sodium houttuynia and erythromycin MICs.The MICs of sodium houttuynia and erythromycin were detected before and after the continuous induction at the starting concentration of 1/2 MIC.The rplD and rplV encoding genes of L4 and L22 were amplified by PCR and sequenced before and after drug induction.The changes of amino acid sequences before and after drug induction were compared.Results The change of MICs of Sp induced by sodium houttuynin was less than 2 times,and no drug-resistant strains were produced.Before induction,the MICs of all strains to erythromycin ranged from 0.125μg/ml to 0.25μg/ml.After induction,ATCC6306 and 5 clinical strains became erythromycin resistant strains,and the MICs ranged from 4μg/ml to 32μg/mL.ATCC6306 and 3 clinical L4 and L22 amino acid sequences showed 1-3 substitution mutations.Conclusion erythromycin induced stable resistance of Streptococcus pneumoniae in vitro,and the resistance mechanism may be related to mutations of L4 and L22 amino acids in ribosomal proteins.Streptococcus pneumoniae was less resistant to sodium houttuynia than the chemically synthesized drug.