目的 探讨我国南方地区鲍曼不动杆菌流行株ST457毒力进化方向。方法 收集南方地区5家大型三甲医院2012年—2015年血和/或痰标本来源的鲍曼不动杆菌菌株,运用不同毒力实验,比较ST457与其他CC92流行克隆株与非流行克隆株的毒力差异。结果 ST457感染患者早期死亡率高;ST457菌株平均产生物膜能力低于ST195和ST208;83.3%的鲍曼不动杆菌临床分离菌株在血清的存活率大于60%,其中43.3%的菌株可在血清内快速繁殖,不同ST型组间、菌血症组和非菌血症组间无差异;不同ST型菌株竞争后,ST457未展现出竞争优势。结论 与传统CC92流行株相比,ST457毒力表型与传统的CC92流行株类似,提示CC92克隆株共进化能力。部分流行株短时间内在血清中快速繁殖,提示其条件致病后潜在的血流感染的能力。

Objective To investigate the virulence of the prevalent clone ST457 of Acinetobacter baumannii in Southern China. Methods Isolates from sputum and/or blood samples from 2012 to 2015 in 5 large differences between clonal complex 92(CC92) and non-CC92 were estimated by biofilm assay, competition assay and serum assay. Results Patients with ST457 infection had high early mortality. The average biofilm production of ST457 was significantly lower than that of ST195 and ST208. In serum assay, 83.3% isolates survived in the serum with over 60% survival rate, of which 43.3% strains reproduced in the serum, with no difference between STs or between bacteremia and non-bacteremia group. After competing with different ST strains, ST457 shows no competitive advantage. Conclusions ST457 had a similar virulence phenotype with the traditional prevalent CC92 clone, suggesting the co-evolutionary ability for CC92 clone. Some clinical isolates were survived in human serum, suggesting the potential capacity of bloodstream infection.

目的 本研究对广州地区5家教学医院的鲍曼不动杆菌进行分子流行病学分析。方法 5家教学医院共采集138株鲍曼不动杆菌,利用多位点序列分型(multilocus sequence typing,MLST)及eBURST算法评价菌株之间的遗传关系。结果 MLST将138株鲍曼不动杆菌分为8个已有序列类型(STs),分别为ST195、ST208、ST457、ST136、ST254、ST548、ST445和ST53,还发现17个新STs。其中ST195的数量最多,占所有分离株的35.5%(49/138),其次为ST208,占所有分离株的21.0%(29/138)。eBURST算法分析显示以ST195为预测祖先型的克隆复合体(clonal complex, CC) 195在医院环境中广泛传播。结论 鲍曼不动杆菌CC195是广州地区的流行克隆,各家医疗机构应根据其自身实际制定感染防控策略。

Objective We analyzed the molecular epidemiology of A.baumannii isolated from 5 teaching hospitals in Guangzhou to identify the epidemic clone in this area. Methods A total of 138 strains of A.baumannii were collected from 5 teaching hospitals, and the genetic relationship was evaluated by multilocus sequence typing (MLST) and eBURST algorithm. Results MLST divided 138 strains of A.baumannii into 8 existing sequence types (STs), namely ST195, ST208, ST457, ST136, ST254, ST548, ST445 and ST53, and 17 new STs. Among them, ST195 had the largest number, accounting for 35.5% (49/138) of all isolates, followed by ST208, accounting for 21.0% (29/138) of all isolates. eBURST algorithm showed that the clonal complex (CC) 195, the predicted founder ST195, was widely spread in the hospital environment. Conclusion A.baumannii CC195 was an epidemic clone in Guangzhou area. Medical institution should develop infection prevention and control strategies according to its own actual conditions.