红霉素耐药肠球菌ermB基因与转座子Tn1545和Tn917的关系

The relationship between ermB gene and transposon Tn1545 and Tn917 in erythromycin-resistant enterococcal isolates

目的研究158株儿童临床标本中分离的肠球菌对红霉素耐药性及其转座子Tn1545和Tn917介导的耐大环内酯类抗生素ermB基因的特点。方法采用琼脂稀释法对红霉素进行最小抑菌浓度(MIC)测定,用PCR检测肠球菌ermB、mefA基因、Tn1545和Tn917。结果158株红霉素MIC_(50)和MIC_(90)都为256μg/ml,红霉素耐药率为94.9%(150株/158株)。在150株红霉素耐药株中,er- mB基因的总携带率为70.7%,其中粪肠球菌、屎肠球菌、坚韧肠球菌、鸟肠球菌和海氏肠球菌其ermB基因的携带率分别为:78.3%、58.1%、100%、100%、100%,粪肠球菌ermB基因的携带率高于屎肠球菌(x^2=6.884,P=0.009);粪肠球菌未检测到mefA基因,只有1株屎肠球菌检测到mefA基因。106株ermB基因阳性红霉素耐药株中,46.2%的菌株ermB基因同时存在于转座子Tn1545和Tn917;ermB基因单纯存在于转座子Tn1545的43株,占40.6%;ermB基因单纯存在于转座子Tn917的1株,占0.9%。结论儿童临床标本中分离出的肠球菌耐大环内酯类抗生素的主要耐药基因为ermB基因,并且ermB基因主要是通过转座子Tn1545来携带其对大环内酯类抗生素的耐药。

Objective To characterize ermB gene transposition by Tn1545 and Tn917 in macrolide-resistant 158 enterecoccal isolates in Beijing Children＇s Hospital. Methods Agar dilution was used to study the drug resistance to erythromycin and polymerase chain reaction was used to test ermB gene, mefA gene, Tn1545 and Tn917 of enterococcal isolates. Results Among all the 158 enterecoccal isolates in pediatrics, MIC50 and MIC50 of erythromycin were same as 256 μg/ml. The total ermB gene carriage rate is 70.7 %, the ermB gene in E. faecalis, E. faecium, E. durans, E. avium and E. hirae accounkxt for 78.3%, 58.1%, 100%, 100%, 100%, respectively. The ermB gene carriage rate in E. faecalis was higher than that in E. faecium. There was no mefA gene in E. faecalis, only one E. faecium was positive for mefA gene. The ermB gene existed only in Tn1545 was 40.6%, the ermB gene existed only in Tn917 was 0.9%. The ermB gene existed in Tn1545 and Tn917 was 46.2%. Condusion Resistance to erythromycin in entereeoccal isolates in Beijing Children＇s Hospital was generally mediated via ermB gene, which was mainly transported by Tn1545 in resistance to macrolide in enteroeoccal isolates.