Pseudomonas aeruginosa modulates Inquilinus limosus tolerance to acute antibiotherapy under cystic fibrosis variable oxygen conditions

Abstract

Cystic Fibrosis (CF) airways disease involves a complex polymicrobial infection whereby different bacterial species can interact and influence each other. To gain insights into the role that Pseudomonas aeruginosa and Inquilinus limosus interactionsmay play during CF infection, the reciprocal effect during biofilm formation, as well as ciprofloxacin activity against mixed biofilms under in vitro atmospheres with different oxygen availabilities were evaluated. The kinetics of biofilm formation showed that P. aeruginosa negatively affected I. limosus growth, under both aerobic and anaerobic environments. On the other hand, under aerobic conditions, I. limosus led to a decrease in biofilm production by P. aeruginosa, although biofilm-cells viability of remains unaltered.Given the differences measured by the crystal violet [biofilm biomass, consisting of both extracellular polymeric substance (EPS) and cells] and the viable count (biofilm viability) assays, these results may indicate that in mixed biofilms the presence of I. limosus, under aerobic conditions, leads to a reduction in P. aeruginosa EPS.Interestingly, P. aeruginosa might be responsible for the protection of I. limosus against ciprofloxacin activity. The analysis of the viable count dynamics revealed that I. limosus is less susceptible to ciprofloxacin when co-cultured in mixed biofilms with P. aeruginosa. Taken together, the results suggest a reciprocal interference between different bacterial species in CF lung. Alterations of bacterial behaviour due to interspecies interactions may be important for disease progression in CF infection.