201. Targeting Acinetobacter species with bacteriophage derived proteins
- Author
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Ferreira, Alice Maria Fernandes, Oliveira, Hugo Alexandre Mendes, Azeredo, Joana, and Universidade do Minho
- Subjects
atividade anti-virulência ,ComputingMilieux_THECOMPUTINGPROFESSION ,Acinetobacter ,antibacterial activity ,atividade antibacteriana ,endolysin ,ComputerApplications_COMPUTERSINOTHERSYSTEMS ,depolymerase ,anti-virulence activity ,endolisina ,GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries) ,depolimerase - Abstract
Dissertation for Master Degree in Biotechnology Supervisor, Acinetobacter species have become a major cause of nosocomial infections worldwide due to its inherent and adaptive resistance towards the majority of antibiotics, survival in hostile environments and virulence traits. The increased mortality rates associated with these hard-to-treat bacteria urgently demands the development of new therapeutic options. In the present work, bacteriophage endolysins and depolymerases were explored to tackle Acinetobacter infections. Five novel enzymes were identified, heterologously expressed in Escherichia coli and characterized to gain insights into their enzymatic and structural features, as well tested in vitro (Acinetobacter cells and human cell line A549) and in vivo (Galleria mellonella) to assess their therapeutic potential. Remarkably, endolysins exhibited intrinsic ability to kill Acinetobacter cells, with optimal activity at pH 5-7 and low ionic strength (20 mM), reducing approximately 3.5 log to > 5 log (below the detection limit) within 2 h. Interestingly, no antibacterial activity of endolysins could be observed in biomatrices such as culture medium. All depolymerases exhibited activity on extracellular polysaccharides in all ranges of pH values (pH 5 to 9) and ionic strengths (0 to 500 mM) and retained at least 50% of the activity at 70 ºC. Consistently, circular dichroism analysis showed moderate and high thermostability of endolysins (rich in α-helices) and depolymerases (rich in β-sheets), with melting temperatures around 56 ºC and > 68 ºC, respectively. Combinations of endolysin and depolymerase reduced 24 h-old bacterial biofilms in approximately 1 log. Further work conducted on depolymerases demonstrated that these enzymes degrade the bacterial capsular polysaccharides (observations confirmed by Atomic Force Microscope). The removal of the capsule via depolymerase activity reduced the virulence of Acinetobacter to human epithelial cells for 2 h. Complementary studies performed in vivo showed that depolymerase was able to rescue Galleria mellonella larvae from Acinetobacter baumannii infection in a time- and dose-dependent manner. Maximal difference survival between larvae injected with depolymerase-treated bacteria and non-treated bacteria was observed after 72 h with 5 μM of depolymerase (88% vs 10%; P < 0.01). In summary, the enzymes studied in this thesis revealed to be effective candidates to control problematic Acinetobacter infections, either as bacteriolytic or anti-virulence agents., As espécies de Acinetobacter tornaram-se uma das principais causas de infeções nosocomiais em todo o mundo, devido à sua resistência inerente e adaptativa à grande maioria dos antibióticos, sobrevivência em ambientes hostis e fatores de virulência. O aumento da taxa de mortalidade associada com estas bactérias de difícil tratamento exige, urgentemente, o desenvolvimento de novas opções terapêuticas. No presente trabalho, endolisinas e depolimerases de bacteriófago foram exploradas para combater infeções de Acinetobacter. Cinco novas enzimas foram identificadas, expressas de forma heteróloga em Escherichia coli e caracterizadas para obter informações sobre as suas características enzimáticas e estruturais, e também, testadas in vitro (células de Acinetobacter e linha celular humana A549) e in vivo (Galleria Mellonella) para avaliar o seu potencial terapêutico. Notavelmente, as endolisinas exibiram capacidade intrínseca para matar células de Acinetobacter, com atividade ótima no pH 5-7 e a baixa força iónica (20 mM), reduzindo aproximadamente 3.5 log até > 5 log (abaixo do limite de deteção) em 2 h. Curiosamente, nenhuma atividade antibacteriana das endolisinas foi observada em biomatrizes, como meio de cultura. Todas as depolimerases exibiram atividade contra os polissacarídeos extracelulares em todas as gamas de valores de pH (pH 5 a 9) e força iónica (0 a 500 mM) e conservaram pelo menos 50% da atividade a 70 ºC. De forma consistente, os estudos em dicroísmo circular mostraram moderada e alta thermoestabilidade das endolisinas (ricas em α-helices) and depolimerases (ricas em β-sheets), com temperaturas de desnaturação de aproximadamente 56 ºC and > 68 ºC, respetivamente. Combinações de endolisina e depolimerase reduziram biofilmes bacterianos de 24 h em aproximadamente 1 log. Estudos adicionais realizados com as depolimerases demonstraram que estas enzimas degradam a cápsula polissacarídica bacteriana (observações confirmadas por microscopia de força atómica). A remoção da cápsula pela atividade da depolimerase reduziu a virulência de Acinetobacter em células epiteliais humanas por 2 h. Estudos complementares realizados in vivo revelaram que a depolimerase foi capaz de resgatar larvas de Galleria Mellonella da infeção de Acinetobacter baumannii, de uma forma dependente do tempo e da dose. A maior diferença de sobrevivência entre larvas injetadas com bactéria tratada com depolimerase e bactéria não tratada foi observada após 72 h com 5 μM de depolimerase (88% vs 10%; P < 0.01). Em suma, as enzimas estudadas nesta tese revelaram ser candidatas eficientes para o controlo de infeções problemáticas de Acinetobacter, quer como agentes antibacteriano ou anti-virulência., This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte and the Project PTDC/BBB-BSS/6471/2014 (FEDER: POCI-01-0145-FEDER-016643).
- Published
- 2017