广泛耐药鲍曼不动杆菌 ST238克隆株毒力及适应性特征

摘要

目的：通过检测广泛耐药鲍曼不动杆菌流行克隆 ST238的毒力和环境适应性﹐探讨该克隆株在当地持续流行的机制。方法比较 ST238克隆株与鲍曼不动杆菌 ATCC 19606的体外生长曲线及竞争指数（competition index﹐CI）﹐试管法测定菌株内明胶酶活性；微量法进行 D-甘露糖抵抗红细胞凝集试验；运动平板法测定蹭行运动能力；结晶紫染色法定量分析生物膜形成能力。小鼠动物模型检测体内致病力。结果 ST238克隆株与标准株间体外生长能力差异无统计学意义（P＞0.05）。培养24 h 时 ST238克隆株与鲍曼不动杆菌 ATCC 19606在体外竞争能力无明显差异（CI=0.29﹐P＞0.05）。明胶酶活性在ST238克隆株与敏感株间分布无差异（P＞0.05）。血凝结果与菌株来源之间差异无统计学意义（P＞0.05）。敏感株的运动能力及生物膜形成能力均强于 ST238克隆株（P＜0.05）。ST238克隆株与标准株的 LD50分别为6.9和6.7 log CFU/mL。接种9.3 log CFU/mL 菌液的小鼠平均死亡时间差异无统计学意义（P＞0.05）。结论 ST238克隆株获得广泛耐药性后﹐其环境适应性无明显下降﹐同时该克隆株的毒力也无明显改变。这种生物学特性可能是该克隆株在当地长期流行的原因之一。%Objective To study the virulence and environmental adaptability of extensively drug-resistant Acinetobacter baumannii (XDRAB) ST238 clone, and explore the potential mechanisms of the persistent prevalence of this clone. Methods MTT method was employed to examine the in vitro growth of these strains. The competition index (CI) were determined by in vitro competition experiment to compare with A. baumannii ATCC 19606. The gelatinase activity, D-mannose related O/AB hemagglutination activity, twitching motility, and biofilm formation were studied to analyze its virulence. The median lethal dose (LD50) was determined for mice in sepsis peritoneal infection model. Results The in vitro growth (P>0.05) or competition experiment (CI=0.29, P>0.05) did not show significant difference between ST238 clone and the reference strain ATCC 19606. The gelatinase (P>0.05) and hemagglutination activity (P>0.05) did not show significant difference between ST238 clone and the susceptible strain. However, the susceptible reference strain ATCC 19606 did show stronger motility and biofilm formation ability than ST238 clone (P<0.05). The LD50 of ST238 clone and reference strain ATCC 19606 was 6.9 and 6.7 log CFU/mL, respectively. There was no significant difference in the mean time to death of mice after challenging with 9.3 log CFU/mL (P>0.05). Conclusions A. baumannii ST238 clone acquired extensively drug-resistant ability but without loss of environmental adaptability and virulence. This biological nature may contribute to its persistent prevalence in our hospital.