Psl多糖介导铜绿假单胞菌和鲍曼不动杆菌的互作机制研究

铜绿假单胞菌（Pseudomonas aeruginosa）是一种临床常见的革兰氏阴性条件致病菌，因其复杂多样的毒力系统以及耐药机制，能引起许多严重的感染性疾病，严重危害了人类健康。近年来，铜绿假单胞菌与其他微生物，比如细菌、病毒、真菌的共同感染，导致病人预后较差的临床现象引起了广泛关注。铜绿假单胞菌与鲍曼不动杆菌（Acinetobacter baumannii）的合并感染常见于重症监护室的患者中，尤其是一些术后抗感染的患者和使用介入性医疗设备的患者，且这些患者往往感染程度较重、预后较差。目前，临床上针对细菌感染的诊断指南往往侧重于实验室中分离的优势致病菌和基于单个物种的抗生素耐药性分析，而忽略了潜在的物种间的相互作用，这可能会产生与单个物种截然不同的新的耐药表型。因此，本课题通过建立铜绿假单胞菌和鲍曼不动杆菌双物种生物被膜模型来研究物种之间相互作用对抗生素治疗的影响。鲍曼不动杆菌临床分离株 R2 是一株生物被膜形成能力较弱，但对多种抗生素呈现耐药的菌株。在双菌株生物被膜药敏实验以及共聚焦显微镜成像实验中，我们发现鲍曼不动杆菌 R2 的存在保护了抗生素敏感的铜绿假单胞菌 PAO1 使得其在 4 倍 MIC 亚胺培南压力下仍然能够形成成熟的生物被膜，同时群落组成也随着外部抗生素压力的变化而变化。我们进一步的研究发现，铜绿假单胞菌 PAO1 生物被膜细胞外基质的组成成分，尤其是 Psl 多糖，在上述菌种间相互作用中发挥了关键作用。Psl 多糖介导了双物种生物被膜的耐药性的增强，特别是对 β-内酰胺类抗生素。另外，我们发现使用 DNase I 降解与 Psl 多糖交联的 eDNA 能够有效的降低双菌株生物被膜的耐药性。因此，以 Psl 多糖的稳定性作为新型抗生素开发的作用靶点，将为多种微生物混合感染的治疗提供全新的思路。

Pseudomonas aeruginosa (P. aeruginosa), a common Gram-negativepathogen, can cause a variety of refractory infectious diseases due to its complexvirulence systems and diverse drug-resistance mechanisms, which poses a greatrisk for public health. For decades, P. aeruginosa has been reported to co-infectwith other microorganisms such as bacteria, virus, and fungi, which often resultsin a poor prognosis for the patients. P. aeruginosa and Acinetobacter baumannii(A. baumannii) co-infection is common in intensive care unit patients,particularly surgical patients, and patients with interventional medical devices,who face the high risk of severe infections. Current clinical guidelines forbacterial infection diagnosis have focused on the isolation and characterizationof pathogenic bacteria in the laboratory and single-species-based antibioticresistance profiling, which underestimate the potential interspecies interactionsthat could lead to novel drug-resistance phenotypes. Here, we investigated theimpacts of interspecies interactions on antibiotics therapies by establishing a P.aeruginosa and A. baumannii dual-species biofilm model. The clinical isolate R2of A. baumannii is a poor biofilm former and resistant to a variety of antibiotics,including imipenem, ceftazidime, ciprofloxacin, tobramycin, and others. In dualspecies biofilms, the community composition shifts with the increase in antibioticdosage, and the presence of A. baumannii R2 protects the antibiotic-sensitive P.aeruginosa PAO1, which can still survive in imipenem up to 4 × MIC. Furtherresearch discovered that the structural components of the P. aeruginosa PAO1biofilm matrix, specifically Psl exopolysaccharide, played an important roleduring interspecies interactions and promoted drug resistance in dual-speciesbiofilms. Furthermore, we discovered that DNase I treatment can degrade eDNAcrosslinked with Psl exopolysaccharide and significantly reduce antibioticresistance in dual-species biofilms. Therefore, our study suggests that targetingPsl stability is a potential approach in controlling polymicrobial infections.

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