Klebsiella pneumoniae peptide hijacks a Streptococcus pneumoniae permease to subvert pneumococcal growth and colonization

Treatment of pneumococcal infections is limited by antibiotic resistance and exacerbation of disease by bacterial lysis releasing pneumolysin toxin and other inflammatory factors. We identified a novel peptide in the Klebsiella pneumoniae secretome, which enters Streptococcus pneumoniae via its AmiA-AliA/AliB permease. Subsequent downregulation of genes for amino acid biosynthesis and peptide uptake was associated with reduction of pneumococcal growth in defined medium and human cerebrospinal fluid, irregular cell shape, decreased chain length and decreased genetic transformation. The bacteriostatic effect was specific to S. pneumoniae and Streptococcus pseudopneumoniae with no effect on Streptococcus mitis, Haemophilus influenzae, Staphylococcus aureus or K. pneumoniae. Peptide sequence and length were crucial to growth suppression. The peptide reduced pneumococcal adherence to primary human airway epithelial cell cultures and colonization of rat nasopharynx, without toxicity. We also analysed the effect of peptide on the proteome of S. pneumoniae. We found alteration of the proteome by the peptide with some proteins turned on or off in line with the transcriptomic changes. We therefore identified a peptide with potential as a therapeutic for pneumococcal diseases suppressing growth of multiple clinical isolates, including antibiotic resistant strains, while avoiding bacterial lysis and dysbiosis.

肺炎链球菌感染的治疗受到抗生素耐药性的限制，且细菌裂解释放的肺炎溶血毒素（pneumolysin toxin）与其他炎症因子会加重疾病病情。我们在肺炎克雷伯菌（Klebsiella pneumoniae）分泌组中鉴定出一种新型肽，该肽可通过AmiA-AliA/AliB通透酶（AmiA-AliA/AliB permease）进入肺炎链球菌（Streptococcus pneumoniae）体内。后续观察到，氨基酸生物合成与肽摄取相关基因的下调，与限定培养基及人类脑脊液中肺炎链球菌生长受抑制、细胞形态异常、链长缩短以及遗传转化能力下降相关。该抑菌效应仅对肺炎链球菌与假肺炎链球菌（Streptococcus pseudopneumoniae）具有特异性，对缓症链球菌（Streptococcus mitis）、流感嗜血杆菌（Haemophilus influenzae）、金黄色葡萄球菌（Staphylococcus aureus）及肺炎克雷伯菌均无作用。肽的序列与长度对生长抑制效果至关重要。该肽可降低肺炎链球菌对原代人类气道上皮细胞培养物的黏附能力以及大鼠鼻咽部的定植能力，且无毒性。我们还分析了该肽对肺炎链球菌蛋白质组（proteome）的影响，发现该肽可改变蛋白质组表达模式，部分蛋白的表达上调或下调与转录组变化相符。综上，我们鉴定出一种具有肺炎链球菌疾病治疗潜力的肽类物质，它可抑制包括抗生素耐药菌株在内的多种临床分离株的生长，同时避免细菌裂解与菌群失调（dysbiosis）。