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
