Publicação
Characterization of novel Acinetobacter baumannii phage-derived depolymerases with anti-virulence properties
| Resumo: | Acinetobacter baumannii is a pathogenic bacterium and is the major cause of nosocomial infections in hospital environment. Treatment of A. baumannii infections with antibiotics is extremely difficult due to their multi-resistance antibiotics. Moreover, most A. baumannii strains carry a capsular polysaccharide that is considered its main virulence factor, and a high variety of capsular types are produced by this bacterium. Phages are viruses that only infect bacteria, using their cellular machinery to propagate. Some phages produce polysaccharide depolymerases, that bind specifically to certain capsular types and degrade the polysaccharides present in the bacterial capsules, allowing phages to infect. Therefore, capsular polysaccharide depolymerases have demonstrated to be a very powerful anti-virulence weapon with the capability to degrade and strip bacterial cells from their capsule. Prior to this work, 17 distinct A. baumannii capsular-specific depolymerases were identified and characterized (K1-2, K9, K19, K27, K30, K32, K37, K44-45, K47-48, K87, K89, K91, K93 and K116). In this study, oxa-51 and oxa-23 β-lactamases-encoding genes were the most predominant found within carbapenem-resistant A. baumannii clinical isolates, followed by Imp-like and oxa-24 β-lactamases-encoding genes. Furthermore, 6 novel phage derived-CPS depolymerases were identified (F70, 3042, 3043, 3060, 3073 and 3082). They were cloned and expressed in E. coli alongside with previously identified CPS depolymerases (B1, B9, P1 and P2). The activity spectra of the capsular depolymerases B1, B3, B9, P1, P2, F70, 3042, 3043 and 3073 matched the lytic spectra of their parental phages (K9, K2/K19, K30/K45, K1, K67, K44, K38 and K32 respectively), expanding the collection of enzymes to infect 19 different K types. However, the capsular depolymerases belonging to phages 3060 and 3082 did not demonstrate any activity against any strain. Furthermore, these enzymes were characterized, demonstrating a high structural stability and degrading activity against the capsular polysaccharides, leaving bacteria more susceptible to be eliminated by the serum’s complement system. However, no synergy was found between the combination of these enzymes and different antibiotics in the disruption of biofilms and in planktonic cells. |
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| Autores principais: | Domingues, Rita Alexandra Carpinteiro |
| Assunto: | Acinetobacter Bacteriophages CPS depolymerases Capsular types Antimicrobial activity Vacteriófagos Depolimerases Tipos capsulares Atividade antimicrobiana Ciências Médicas::Biotecnologia Médica |
| Ano: | 2021 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Acinetobacter baumannii is a pathogenic bacterium and is the major cause of nosocomial infections in hospital environment. Treatment of A. baumannii infections with antibiotics is extremely difficult due to their multi-resistance antibiotics. Moreover, most A. baumannii strains carry a capsular polysaccharide that is considered its main virulence factor, and a high variety of capsular types are produced by this bacterium. Phages are viruses that only infect bacteria, using their cellular machinery to propagate. Some phages produce polysaccharide depolymerases, that bind specifically to certain capsular types and degrade the polysaccharides present in the bacterial capsules, allowing phages to infect. Therefore, capsular polysaccharide depolymerases have demonstrated to be a very powerful anti-virulence weapon with the capability to degrade and strip bacterial cells from their capsule. Prior to this work, 17 distinct A. baumannii capsular-specific depolymerases were identified and characterized (K1-2, K9, K19, K27, K30, K32, K37, K44-45, K47-48, K87, K89, K91, K93 and K116). In this study, oxa-51 and oxa-23 β-lactamases-encoding genes were the most predominant found within carbapenem-resistant A. baumannii clinical isolates, followed by Imp-like and oxa-24 β-lactamases-encoding genes. Furthermore, 6 novel phage derived-CPS depolymerases were identified (F70, 3042, 3043, 3060, 3073 and 3082). They were cloned and expressed in E. coli alongside with previously identified CPS depolymerases (B1, B9, P1 and P2). The activity spectra of the capsular depolymerases B1, B3, B9, P1, P2, F70, 3042, 3043 and 3073 matched the lytic spectra of their parental phages (K9, K2/K19, K30/K45, K1, K67, K44, K38 and K32 respectively), expanding the collection of enzymes to infect 19 different K types. However, the capsular depolymerases belonging to phages 3060 and 3082 did not demonstrate any activity against any strain. Furthermore, these enzymes were characterized, demonstrating a high structural stability and degrading activity against the capsular polysaccharides, leaving bacteria more susceptible to be eliminated by the serum’s complement system. However, no synergy was found between the combination of these enzymes and different antibiotics in the disruption of biofilms and in planktonic cells. |
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