Biomarkers and therapeutic targets based on bacterial “Quorum Sensing” system
[eng] Infectious diseases are still one of the main leading causes of death worldwide mainly due the overuse and the lack of development of new antibiotics. This fact has increased the appearance of multidrug resistance (MDR) bacteria strains resulting in a growing number of infections difficult to...
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| Formato: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2022 |
| País: | España |
| Recursos: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/189700 |
| Acesso em linha: | https://hdl.handle.net/2445/189700 http://hdl.handle.net/10803/675602 |
| Access Level: | acceso abierto |
| Palavra-chave: | Malalties infeccioses Bacteriologia Immunoquímica Immunoglobulines Communicable diseases Bacteriology Immunochemistry Immunoglobulins |
| Resumo: | [eng] Infectious diseases are still one of the main leading causes of death worldwide mainly due the overuse and the lack of development of new antibiotics. This fact has increased the appearance of multidrug resistance (MDR) bacteria strains resulting in a growing number of infections difficult to treat with conventional drugs. In this context, Pseudomonas aeruginosa gram negative bacterium presents great interest since it is a MDR bacterium causing a high number of infections, especially nosocomial infections. Moreover, it is one of the most predominant pathogen in patients with cystic fibrosis. Usually, P. aeruginosa infections can be categorized as acute and chronic, but this classification is not always obvious. Acute infections are frequent during early stages of infection and associated with a planktonic lifestyle and with high levels of virulence factors (VFs) production. In contrast, chronic infections are characterized by a lower VF production and the formation of biofilms and persiter cells, which confer high resistance to antibiotics. The development of pathogenesis and the transition between acute and chronic infections are regulated by a bacterial communication system called Quorum Sensing (QS), which controls the expression of a myriad of genes in response to the presence of small signal molecules called autoinducers. In consequence, QS has attracted attention as a promising target to develop diagnostic and therapeutic approaches. Although being a time-consuming technique, which delays treatment administration with the consequences that this entails, the gold standard technique used for P. aeruginosa detection is still based on plate culture. Thus, there is a clear need to obtain rapid and sensitive diagnostic techniques. Within this framework, a highly sensitive, specific and rapid immunochemical assay has been developed to detect one of the main VF of P. aeruginosa, pyocyanin (PYO), in less than 2 h using a high affinity monoclonal antibody (mAb) against it. The low limit of detection of the assay has allowed PYO detection in bacterial isolates from patients infected with P. aeruginosa and its validation as potential biomarker of these infections. In the light of the obtained results, further investigations have been assessed on analysing directly clinical samples, such as sputa and swab samples from patients infected with this pathogen. Furthermore, based on QS system and on the use of specific mAbs against key molecules of this system, a new therapeutical approach to treat P. aeruginosa infections has been studied. In this context, the quenching activity of PYOmAb has been assessed using a developed cell based in vitro system. First, the cytotoxic effect caused by PYO has been evaluated on murine macrophages studying different hallmarks of viability since this VF is known to exert a large number of toxic effects in host cells. Subsequently, the protective effect of PYOmAb on the same cell line has been analysed obtaining a high increase of viability percentages (50 - 80 %). Apart from studying an effector molecule, the quenching of a signalling molecule, such as Pseudomonas Quinolone Signal (PQS), has been also adressed using the same in vitro system. In this case, the protection levels obtained have been even better reaching 80 - 100 % viability levels. Thus, the obtaines results has demonstrated the potential of these mAbs as therapeutic agents. |
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