肺炎链球菌介导大环内酯类及四环素双重耐药性相关元件的研究

Gene elements of dual-resistance to macrolides and tetracycline mediated by streptococcus pneumoniae

目的研究介导肺炎链球菌临床分离株耐大环内酯和四环素药物的基因元件特点。方法 48株耐红霉素肺炎链球菌以PCR检测大环内酯类耐药基因ermB、ermTR、mef与四环素耐药基因tetM及转座子家族Tn916整合酶int,聚合酶链式反应-限制片段长度多态性(RFLP)鉴定mefA和mefE。结果全部菌株均未发现ermTR和mefA基因,48株耐红霉素肺炎链球菌中,仅1株(2.1%)未检出ermB和mefE基因,其余47株均检出ermB和(或)mefE基因,其中ermB 50.0%,ermB+mefE为45.8%及mefE 2.1%;ermB和mefE基因在耐药株中的阳性率分别是95.8%和47.9%;48株肺炎链球菌均检出tetM,int在46株肺炎链球菌中检出占95.8%;45株(93.7%)肺炎链球菌同时存在int、四环素抗性基因和红霉素抗性基因,其中int+tetM+ermB为47.9%,int+tetM+ermB+mefE为45.8%。结论 ermB编码23S rRN(A)甲基化酶致靶位改变是肺炎链球菌对大环内酯药物耐药的主要机制,其次是mefE基因表达主动外排系统导致对大环内酯药物耐药,接合性转座子家族Tn916可能是介导肺炎链球菌对大环内酯类药物、四环素等药物耐药的重要机制之一,并在选择压力下导致耐药菌的广泛传播。

OBJECTIVE To investigate characteristic of gene element mediated Streptococcus pneumoniae resistance to macrolides and tetracycline.METHODS PCR tests of macrolide-resistance genes-ermB,ermTR and mef,tetracycline-resistance genes tetM and int gene（integrase） of conjugative transposons Tn916 family were performed in 48 macrolide and tetracycline-resistant S.pneumoniae isolates.mefA and mefE were distinguished by PCR-restriction fragment length polymorphism analysis（PCR-RFLP）.RESULTS All of the isolates didnot carried ermTR and mefA.ermB and/or mefE presented in 48 erythromycin-resistant strains except one isolate（2.1%）,with ermB（＋）50.0%,ermB＋mefE（＋）45.8% and mefE（＋）2.1%.The positive rates of ermB and mefE in erythromycin-resistant strains were 95.8% and 47.9%,respectively.All of the isolates had tetM,while 95.8% had int of the 48 isolates.The co-presence of macrolide-resistance genes tetracycline-resistance genes and int gene was found in 45 isolates（95.7%）,mainly with two patterns,int＋ tetM＋ermB 47.9% and int＋tetM＋ermB＋mefE 45.8%,respectively.CONCLUSION Resistance to macrolide in Streptovoccus pneumoniae is generally mediated by methylation of 23S rRNA via ermB methylase,and gene mefE seems to be less important.The mechanic of macrolide-resistance and tetracycline-resistance is significantly associated with conjugative transposons Tn916 family which induced the widespread of drug-resistance.