北京儿童医院14型肺炎链球菌耐药性分析及分子流行病学研究

Antibiotic suceptibility and molecular epidemiology of serotype 14 Streptococcus pneumoniae isolated from children in Beijing Children's Hospital

目的了解14型肺炎链球菌的抗生素敏感性及分子流行病学特征。方法以北京儿童医院1997—2010年分离自儿童鼻咽拭子的14型肺炎链球菌分离株为研究对象,采用E-test法和纸片扩散法检测菌株对11种抗生素的敏感性,采用多位点序列分型(MLST)确定菌株序列型(ST),eBURST软件分析确定克隆群(CC)。聚合酶链式反应(PCR)检测红霉素耐药基因ermB和mefA,扩增并测序二氢叶酸还原酶基因dhfr。结果肺炎链球菌分离株中14型所占比例在监测期间升高,从1997—1999年的3.9%升高至2010年的9.3%。61株14型肺炎链球菌均对青霉素、阿莫西林-克拉维酸、头孢曲松敏感,但MIC50、MIC90和最大MIC值在监测期间升高。头孢呋辛不敏感率从1997—1999年的0上升至2010年的84.6%。61株均对红霉素耐药,携带ermB基因,4株(6.6%)同时携带mefA基因。36株磺胺耐药菌株均携带Ile100-Leu变异。MLST共分出11种STs,ST875最常见(32株,占52.5%),其次是ST876(13株,占21.3%)。从1997到2010年,CC875的构成比下降(从1997—1999年的100%降为2010年的0),CC876的构成比升高(从1997—1999年的0升至2010年的92.3%)。CC876对β-内酰胺类抗生素耐药性明显高于CC875。结论 1997年到2010年肺炎链球菌中14型的构成比升高,14型菌株对β-内酰胺类抗生素耐药性增强,与具有高β-内酰胺类抗生素耐药性的克隆群CC876的播散有关。

Objective To investigate the genetic structure of serotype 14 Streptococcus pneumoniae （S.pneumoniae） isolated from children with acute respiratory infections during two periods： from 1997 to 2006, and in 2010, in Beijing Children＇s Hospital Methods The serotype 14 isolates were characterized by antibiotic susceptibility using E-test and disk diffusion method. The macrolide resistance genes ermB and mefA were tested by PCR. The dihydrofolate reduc- tase （dhfr） gene sequence and muhilocus sequence typing （MLST） were determined. Results The percentage of sero- type 14 in S.pneumoniae isolates increased from 0% in 1997-1999 to 9.3% in 2010. All the 61 serotype 14 S.pneumoni- ae isolates were susceptible to penicillin, amoxicillin-clavulanic acid and cefiriaxone, but their MICS0 and MICg0 in- creased in this period. The non-susceptibility rate to cefuroxime increased from 0% in 1997-1999 to 84.6% in 2010. All the isolates were resistant to erythromycin and carried the ermB gene, and 4 isolates （6.6%） carried mefA gene addition- ally. All sulfamethoxazole-trimethoprim resistant isolates contained the Ilel00-Leu mutation. Totally 11 STs were identi- fied, among which ST875 was the most prevalent one （52.5%）, followed by ST876 （21.3%）. From 1997 to 2010, thepercentage of CC876 among serotype 14 S.pneumoniae isolates increased from 0% in 1997-1999 to 92.3% in 2010, whereas CC875 decreased from 100% to 0%. CC876 showed higher resistance to β-1actam antibiotics than CC875. Conclusion The percentage of serotype 14 in S.pnenmoniae isolates increased from 1997 to 2010 in Beijing with increasing resistance to β-laetam antibiot-ics, which is assicated with the spread of CC876 with higher resistance under the antibiotics slective pressure.