Identifying and inhibiting co-aggregation occurring between bacterial respiratory pathogens and commensal species associated with the altered microbiota of chronic pulmonary disease to identify the effect on the development of multispecies biofilms in vitro

Comparisons of pulmonary microbiotas associated with healthy individuals and cystic fibrosis (CF) patients identified a less diverse microbiota among CF patients comprising numerous bacterial species not found among healthy controls. This research aimed to identify if coadhesion occurs between respiratory pathogens P. aeruginosa and S. aureus and some commensal species associated with the microbiota of CF. This was conducted in vitro by spectrophotometric co-aggregation analysis and multi-species biofilm assays in the presence and absence of an inhibitor of lectin-mediated coaggregation, testing the ability of eleven commensal representative species of the CF pulmonary microbiota. Results show that all commensal species selected to represent genera that are associated with the CF pulmonary microbiota are capable of coaggregation in vitro with respiratory pathogens, Pseudomonas aeruginosa and Staphylococcus aureus. S. aureus co-aggregated with a higher affinity to commensal species than P. aeruginosa with a median coaggregation percentage of 62.9 % after 24 h incubation, compared to 41.9 % in P. aeruginosa. When commensal and pathogenic species were cultured in the presence of lactose, biofilm inhibition was observed in 5 of 12 cultures with P. aeruginosa and 7 of 12 with S. aureus. These results demonstrate that some commensals associated with CF participate in coaggregation with respiratory pathogens in vitro which has the ability to alter biofilm production. Identifying coadhesion between commensal and pathogenic species in vitro suggests that coadhesion could be occurring in vivo potentially causing increased susceptibility of the host by enhancing adhesion to the epithelial surface of the respiratory tract, aiding colonization and therefore increased susceptibility to infections.