钼酸盐转运体ModABC促进肺炎克雷伯菌肌肉感染及其治疗新思路

Molybdate transporter ModABC contributes to Klebsiella pneumoniae muscle infection and new insight into its treatment

摘要:

[背景] 肺炎克雷伯菌（肺克）是医院感染和社区获得性感染的重要病原菌，由于近年来肺克菌株耐药情况越来越严重，使得其感染在临床治疗上更加棘手。目前肺克感染引起化脓性肌炎的罕见病例越来越多，而深层肌肉组织感染可能会形成厌氧环境，钼酸盐转运体ModABC是细菌厌氧硝酸盐呼吸所必需。前期研究发现ModA可能与肺克毒力正相关。[目的] 研究钼酸盐转运体ModABC对肺克肌肉感染的作用及钨酸盐治疗的可能性。[方法] 构建modA无痕缺失突变株与回补株，通过检测体外厌氧生长、硝酸还原酶活性和小鼠肌肉感染实验分析ModABC对肺克肌肉感染的作用及机制；通过钨酸盐处理（体外、体内）探讨钨酸盐治疗肺克肌肉感染的可能性及疗效。[结果] 成功构建了modA无痕缺失突变株与回补株，发现modA基因敲除后肺克体外厌氧生长明显被极大地抑制、硝酸还原酶活性显著降低，小鼠肌肉脓肿模型显示敲除株ΔmodA感染肌肉脓肿大大消减，并且在肌内生长及侵袭受限；体外钨酸盐处理能够抑制野生株WT厌氧硝酸盐呼吸，在肌肉脓肿模型中也能显著抑制WT生长，但对敲除株ΔmodA无影响。[结论] 钼酸盐转运体ModABC通过增强侵袭力和促进厌氧硝酸盐呼吸来提供适应优势而促进肺克肌肉感染，钨酸盐可以降低由ModA赋予的适应优势而对肺克肌肉感染具有一定的治疗作用。本研究有助于阐明钼离子对肺克致病性的作用机制及为其治疗提供新思路，为深入研究肺克尤其是耐碳青霉烯高毒力肺克感染的治疗奠定基础。

Abstract:

[Background] Klebsiella pneumoniae (Kp) is a major pathogen that causes nosocomial infections and community-acquired infections. In recent years, drug resistance in Kp has become more and more serious, making its treatment less effective. So it becomes a challenge in clinical treatment. At present, more unusual cases of pyomyositis caused by Kp have been reported. Infection in deep muscle may form an anaerobic environment. The molybdate transporter ModABC is essential for bacterial anaerobic nitrate respiration. Previous studies showed that ModA might be positively correlated with Kp virulence. [Objective] To investigate the effect of molybdate transporter ModABC on Kp muscle infection and the potential use of tungstate in treatment. [Methods] The modA traceless deletion mutant and complementary strain were constructed. Then the effect and mechanism of ModABC on Kp muscle infection were analyzed by monitoring anaerobic growth, nitrate reductase activity in vitro and mouse muscle infection experiments in vivo. The possibility and efficacy of tungstate treatment for Kp muscle infection were discussed in this study. [Results] The modA traceless deletion mutant and complementary strain were successfully constructed. This study found that deletion of modA led to significantly inhibited anaerobic growth of Kp and reduced nitrate reductase activity in vitro. The knockout strain ΔmodA showed greatly reduced muscle abscess, intramuscular growth and invasion in mouse muscle abscess model. In vitro tungstate treatment inhibited the anaerobic nitrate respiration of wild strain WT, and also significantly inhibited the growth of WT in muscle abscess model, but had no influence on strain ΔmodA. [Conclusion] The molybdate transporter ModABC contributes to Kp muscle infection by providing fitness advantage through enhancing invasiveness and promoting anaerobic nitrate respiration. Tungstate can reduce the fitness advantage conferred by ModA and has a certain therapeutic effect on Kp muscle infection. This study is helpful to elucidate the mechanism of molybdenum's effect on the pathogenicity of Kp. It also provides new insight into the treatment, laying a foundation for further studies, especially carbapenem-resistant hypervirulent Kp infection.