In vivo longinfectie modellen voor de evaluatie van nieuwe antibacteriële therapieën tegen Pseudomonas aeruginosa en Burkholderia cepacia complex species
23 mei 2017
Campus Drie Eiken - Gebouw Q - Promotiezaal - Universiteitsplein 1 - 2610 Antwerpen (Wilrijk) (route: UAntwerpen, Campus Drie Eiken
16.30 - 18.30 uur
Doctoraatsverdediging Bieke Vanhoutte - Departement Farmaceutische Wetenschappen
In vivo lung infection models for the evaluation of novel antibacterial therapies against Pseudomonas aeruginosa and Burkholderia cepacia complex species
Pseudomonas aeruginosa, Burkholderia cenocepacia and Burkholderia multivorans cause recurrent and chronic respiratory tract infections in patients suffering from cystic fibrosis. Although individually treatable, infections caused by those Gram-negative bacteria can lead to respiratory failure and lung transplantation or death. The antimicrobial resistance and persistence mechanisms against the intensive antibiotic therapies contribute to the survival of those pathogens in the lungs of cystic fibrosis patients. Therefore, the development of alternative antimicrobial therapies such as antimicrobial potentiators is urgently needed.
The general aim of this PhD thesis was the optimization and characterization of mouse lung infection models to evaluate potential new antibacterial therapies against P. aeruginosa and B. cepacia complex species (i.e. B. cenocepacia and B. multivorans). Those mouse lung infection models were characterized by studying the course of infection (i.e. bacterial proliferation in lung, liver and spleen) and the efficacy of the reference antibiotic tobramycin. Furthermore, the local immune response and histological changes in lung tissue were also studied during infection and treatment but only in the B. cenocepacia model. The three optimized mouse lung infection models were characterized by a reproducible course of infection and a two log reduction in lung burden when infected mice were treated with tobramycin. In the last part of this thesis, the efficacy of an alternative antimicrobial strategy was evaluated for
B. cenocepacia lung infections using in vitro and in vivo models. A screening of the NIH Clinical Collection was performed against in vitro B. cenocepacia biofilms in the presence of tobramycin to identify repurposing candidates with potentiator activity. The efficacy of selected hits was evaluated in a three-dimensional organotypic human lung epithelial cell culture model. The in vivo effect was evaluated in the invertebrate Galleria mellonella and in the optimized and characterized B. cenocepacia lung infection mouse model. The screening resulted in 60 hits that potentiated the activity of tobramycin against B. cenocepacia biofilms, including four imidazoles of which econazole and miconazole were selected for further investigation. Unfortunately, a potentiator effect was not observed in the 3D organotypic human lung epithelial cell culture model. Combination treatment was also not able to increase survival of infected G. mellonella and to decrease bacterial lung burden in mice. Although potentiators of tobramycin with activity against biofilms of B. cenocepacia were identified in a repurposing screen, the in vitro activity could not be confirmed nor in a more sophisticated in vitro model, neither in vivo. However, the optimized and characterized mouse lung infection models are now available as a tool for therapeutic research to fight bacterial lung infections.