ABSTRACT

To investigate the virulence of capsular polysaccharide export protein (Wza) in carbapenem-resistant Acinetobacter baumannii and its effect on capsule formation.

wza gene knockout and complementation strains were constructed, and changes in bacterial virulence were observed using in vitro adhesion, antiserum complement killing, anti-oxidation experiments, and infections in Galleria mellonella and mice. The effect of wza knockout on the genes wzb and wzc and wzi were assessed by RT-PCR.

We successfully constructed wza knockout and complementation strains. Compared with wild-type (WT) strains, wza knockout strains displayed lower adhesion to A549 cells (p = 0.044), lower antiserum complement killing ability (p = 0.001), and lower mortality of G. mellonella (p = 0.010) and mice (p = 0.033). Expression levels of wzb, wzc and wzi were decreased in wza knockout strains. The antioxidant capacity of Wza knockout bacteria was only slightly decreased. Complementation of the wza gene returned the adhesion ability, antiserum complement killing ability, and mortality of G. mellonella and mice to WT levels. Expression of wzb, wzc and wzi was also returned to WT levels following wza complementation.

The results clearly demonstrate that Wza is toxic. Wza affects the expression of other proteins of the Wzy capsule polysaccharide synthesis pathway, which affects the assembly, export, and extracellular fixation of capsular polysaccharide, resulting in synergistic effects that decrease bacterial virulence.

摘要

研究荚膜多糖出口蛋白（Wza）在耐碳青霉烯的鲍曼不动杆菌中的毒力及其对胶囊形成的影响。

构建了wza基因敲除和互补菌株，并利用离体粘附，抗血清补体杀伤，抗氧化实验以及在梅勒廊和小鼠中的感染观察了细菌毒力的变化。的效果WZA敲除的基因WZB和WZC和WZI通过RT-PCR评估。

我们成功构建了wza基因敲除和互补菌株。与野生型相比（WT）的菌株，WZA敲除菌株显示降低的粘合性A549细胞（p = 0.044），降低抗血清补体杀伤能力（p = 0.001），和较低的死亡率蜡螟（p = 0.010）和小鼠（p＝ 0.033）。在wza敲除菌株中wzb，wzc和wzi的表达水平降低。Wza敲除细菌的抗氧化能力仅轻微降低。wza的补充该基因使粘附力，抗血清补体的杀伤能力以及病菌（G. mellonella和mic e）的死亡率恢复到WT水平。wza互补后，wzb，wzc和wzi的表达也恢复至WT水平。

结果清楚地表明Wza有毒。WZA水净化影响的表达- [R的WZY荚膜多糖的合成途径，从而影响组装，出口，和胞外荚膜多糖的固定，导致减少细菌毒力的协同作用的蛋白。