Pseudomonas aeruginosa induz pneumonia severa em modelo murino de infecção levando a danos pulmonares e sepse letal

Abstract

Pseudomonas aeruginosa is a common environmental bacterium, found in soil, water and hospitals, capable of causing serious infections in immunocompromised or hospitalized individuals. When it infects the lungs, it can lead to illnesses such as pneumonia, manifested by fever, cough, shortness of breath and chest pain. The objective of this study was to evaluate the potential virulence of the clinical isolate of P. aeruginosa VAP112 in a pulmonary infection model. Initially, an antimicrobial sensitivity test was carried out to evaluate the resistance profile, as well as the detection of virulence (exoU, exoT, exoS, phzI, phzM, oprI, lasA, apr, pilA, pilB, lasB, lasB, plcH, plcN, oprL and ehaJ) and resistance genes (Oxa23, Oxa51, KPC, CTX-M, SHV, NDM-1, ampC, TEM) by PCR. Subsequently, biofilm production was evaluated, as well as the virulence profile of VAP112, in vivo, using both Tenebrio molitor larvae and C57BL/6 mice. For the pneumonia model, the animals were instilled intratracheally with 40 µL of VAP112 at a concentration of 1.5 x 107 CFU/mL and their survival was monitored every 12 hours for 5 days. Another group of animals was euthanized after 24 hours to collect biological samples, which were used for cell quantification, the evaluation of immunological and histological parameters, as well as the quantification of bacterial load in tissues. Using PCR, it was possible to detect the presence of virulence (exoU, exoT, exoS, phzI, phzM, oprI) and resistance (OXA-23, OXA-51) genes. VAP112 was capable of forming biofilm and causing high lethality in T. molitor larvae. In experimental pneumonia, bacterial infection significantly affected the survival of animals, causing pneumonia accompanied by lethal sepsis. It was possible to observe a significant drop in total leukocytes and an increase in cells in the marrow and bronchoalveolar lavage, as well as the spread of bacteria from the lung to the blood circulation and to other organs such as the blood, liver and kidneys. Furthermore, there was a significant increase in the production of nitric oxide in both blood and bronchoalveolar lavage, as well as the inflammatory cytokine IL-6, in animals infected with VAP112. Histological analysis of the infected group showed the presence of lesions characteristic of pneumonia, with inflammatory infiltrate, multifocal areas of edema, and mild to moderate congestion. Therefore, these findings indicate that P. aeruginosa VAP112 was capable of inducing severe pneumonia in animals with rapid progression to sepsis, demonstrating the sample's great potential for virulence and its importance in the clinical context.