Bala Anju, Chhibber Sanjay, Harjai Kusum
Department of Microbiology, BMS Block, Panjab University, Sector 14, Chandigarh 160014, India.
Department of Microbiology, BMS Block, Panjab University, Sector 14, Chandigarh 160014, India.
Int J Med Microbiol. 2014 Nov;304(8):1199-208. doi: 10.1016/j.ijmm.2014.08.013. Epub 2014 Sep 1.
Pseudomonas aeruginosa is an opportunistic pathogen which employs quorum sensing system to regulate several genes required for its survival and pathogenicity within the host. Besides acylhomoserine lactone (AHL) mediated las and rhl systems, this organism possesses Pseudomonas quinolone signalling (PQS) system based on alkyl quinolone signal molecules. The quinolone system represents another layer of sophistication in the complex quorum sensing cascade. Therefore, in the present study, we evaluated the contribution of the PQS system in the establishment of acute urinary tract infection (UTI) in the mouse model. For this, wild-type parent strain of P. aeruginosa MPAO1 and its isogenic single transposon mutant strains pqsH and pqsA were employed to induce UTI in mice. PQS molecules in the tissue homogenates of mice were detected by high performance thin layer chromatography (HP-TLC) method. Virulence of strains was assessed in terms of bacteriological count, histopathological lesions in the renal and bladder tissue and generation of pathological index markers like reactive nitrogen intermediates and malondialdehyde. HP-TLC analysis showed presence of PQS molecules in the renal and bladder tissue of mice infected with MPAO1 while no PQS was detected in case of pqsH and pqsA mutant strains. Results indicated that MPAO1 possessing fully functional PQS biosynthetic genes was highly virulent and caused acute pyelonephritis with severe inflammation and tissue destruction. On the contrary, significant reduction in the log count, mild tissue damage and declined levels of pathological markers were observed in mice infected with mutant strains as compared to MPAO1. Further among mutants, all these parameters were maximally impaired in the pqsA mutant in which synthesis of alkyl quinolones was completely abolished due to the transposon mutation in respective gene. Virulence of the pqsH mutant strain was lesser than that of the MPAO1 but higher than pqsA mutant. In addition, the levels of locally generated pro- and anti-inflammatory cytokines were also found to be low in the renal homogenates of mice infected with the mutant strains. Further, supplementation of strains with PQS resulted in significant enhancement in the virulence as indicated by increased bacterial load, severe histopathological damage and enhanced levels of pro-inflammatory cytokines. These findings provide a new insight into the relevant importance of the Pseudomonas quinolone signalling system in the acute UTI caused by P. aeruginosa. This system can be a potential target for futuristic anti-infective approach against this organism.
铜绿假单胞菌是一种机会致病菌，它利用群体感应系统来调控其在宿主体内存活和致病所需的多个基因。除了由酰基高丝氨酸内酯（AHL）介导的las和rhl系统外，该菌还拥有基于烷基喹诺酮信号分子的铜绿假单胞菌喹诺酮信号（PQS）系统。喹诺酮系统代表了复杂群体感应级联反应中的另一层复杂性。因此，在本研究中，我们评估了PQS系统在小鼠模型急性尿路感染（UTI）发生过程中的作用。为此，使用铜绿假单胞菌MPAO1的野生型亲本菌株及其同基因单转座子突变株pqsH和pqsA来诱导小鼠发生UTI。通过高效薄层色谱（HP-TLC）法检测小鼠组织匀浆中的PQS分子。从细菌计数、肾脏和膀胱组织的组织病理学损伤以及活性氮中间体和丙二醛等病理指标标志物的产生等方面评估菌株的毒力。HP-TLC分析显示，感染MPAO1的小鼠肾脏和膀胱组织中存在PQS分子，而pqsH和pqsA突变株则未检测到PQS。结果表明，具有完整功能PQS生物合成基因的MPAO1具有高毒力，可引起急性肾盂肾炎，并伴有严重炎症和组织破坏。相反，与MPAO1相比，感染突变株的小鼠细菌对数计数显著降低、组织损伤较轻且病理标志物水平下降。此外，在突变株中，由于相应基因的转座子突变导致烷基喹诺酮合成完全被阻断，所有这些参数在pqsA突变株中受损最为严重。pqsH突变株的毒力低于MPAO1，但高于pqsA突变株。此外，在感染突变株的小鼠肾脏匀浆中，局部产生的促炎和抗炎细胞因子水平也较低。此外，用PQS补充菌株后，细菌载量增加、严重组织病理学损伤以及促炎细胞因子水平升高，表明毒力显著增强。这些发现为铜绿假单胞菌喹诺酮信号系统在急性UTI中的相关重要性提供了新的见解。该系统可能成为针对该菌未来抗感染方法的潜在靶点。
