Study of Pyocyanin induced virulence & pathogenicity of nosocomial infectious agent Pseudomonas aeruginosa and its prevention

Abstract

Pseudomonas aeruginosa is a ubiquitously distributed and often, nosocomial infectious agent. It is identified as one of the top three nosocomial infectious agents, causing complicated and persistent infections. It has notorious infection feactures such as biofilm formation and antibiotic resistance, making it a significant healthcare challenge. P. aeruginosa is equipped with a diversified arsenal of virulence factors which help in infection establishment and progression against the host immune system. Among many other, P. aeruginosa produces Pyocyanin (PCN), a redox active blue phenazine pigment, considered to be its primary virulence factor. This blue pigment plays a critical role in infection establishment and survival of the pathogen. Studies have implicated PCN with multiple bioactive properties due to its redox active potential, i.e. immuno-modulation, pro-apoptotic, enzyme inactivation and others. The ability to diffuse through biological membranes imparts a new dimension for PCN mediated virulence of P. aeruginosa in the host body. So far PCN mediated virulence has been considered as localized incidence at the site of infection i.e. effect of PCN on the ciliary movement of epithelial lining or inactivation of DUOX1 enzyme in the respiratory system. The emergence of Pan-drug resistant or ‘Superbug strains’ at pandemic scale is a critical threat to health care setups. The ineffectiveness of antibiotics against P. aeruginosa puts the vulnerable groups at serious risk as the World Health Organization is foreseeing the dawn of Post-antibiotic era. Lack of preventive vaccines against P. aeruginosa is another challenge that puts vulnerable groups at greater risk. A comprehensive strategy was devised to better understand PCN mediated P. aeruginosa virulence. This dissertation reports the potential impact of PCN in Central Nervous System during P. aeruginosa infection. Cytotoxic impact of PCN was studied in xxi murine models. Blood brain barrier permeability was assessed computationally and confirmed via HPLC. Murine behavioral tests demonstrated neurodegenerative and cognitive impairment potential of PCN. Systemic redox potential was evaluated by employing multiple in silico tools and glutathione-S-transferase assay, PCN-induced oxidative stress in brain, lungs and cardiac tissues. For dealing with PCN-mediated virulence, PCN biosynthesis was targeted via drug repurposing in a dual manner: 1) Study of PCN chemical-protein and drug-drug interactions revealed Piperaquine as an anti-virulence therapeutic agent as it has an effective anti-PCN potential. While the structure based study demonstrated aspirin’s potential in inhibiting PCN, unlike ibuprofen. 2) Innate immune component DUOX1 and its homologue NOX4 capable of inactivation of PCN were computationally studied for their sequential, structural and functional aspects, and were annotated. These two schemes could contribute towards the development of Pseudomonas specific anti-virulence approaches independent of antibiotic resistance phenomenon. In a bigger scenario genomic data was explored for dealing with the antibiotic resistance challenge. Using reductive genomic screening, potential peptide vaccine candidates and prospective novel drug targets were predicted. This dissertation focuses on PCN mediated virulence of P. aeruginosa and strategies for prevention and management of infection.