P241 Using an in vitro model to investigate the microbiomes of people with cystic fibrosis

The aim of the work is to investigate the establishment of microbiomes and their interaction with the human host and to better understand the infection processes underlying the chronicity and progression of cystic fibrosis. To properly understand CF and to improve future treatment it is necessary to investigate the consequences of dysfunctional microbiomes and understand how different bacterial species affect each other during infections. To study the interactions between bacteria and the host, we use a model mimicking the human airway epithelium. This consists of epithelial cells cultured at the air-liquid interface (ALI) and represents a fully differentiated ciliated columnar epithelium. Based on the prevalence in CF airways, we initially focus on the bacteria: P. aeruginosa, S. aureus (MSSA and MRSA) and S. pneumoniae. We infect the ALI model with single species and in combinations and monitor both bacterial behavior and host responses. People with CF often encounter S. aureus infections prior to P. aeruginosa and we also work to model this order of arrival. We have created a system, which can be used to study the infections of human epithelial cells with S. aureus, P. aeruginosa and S. pneumoniae. We have established a timeline to study both early and late infection events and found obvious differences in the infection patterns between species and between strains. Microscopy work shows different invasion patterns of all strains with P. aeruginosa and S. aureus MRSA being the most aggressive bacteria resulting in early damage of the human cells. We have found that co-infections with P. aeruginosa and MSSA results in eradication of the MSSA but to a lesser extent the MRSA. We have established an In vitro model system to study infections of human epithelial cells by multiple bacteria species. In the future our model will be improved to include more species and even better reflect the CF microbiomes.