Biophysical properties of biofilm structure
(exopolysaccharide matrix) associated with reduced susceptibility to
antibiotics limits the effective eradication of bacteria, for example, Pseudomonas aeruginosa in cystic
fibrosis. It is suggested that only the surface layers of biofilm is exposed to
a lethal dose of the antibiotic due to diffusion barrier. The efficient
eradication of bacteria forming biofilm may be supported by lytic bacteriophages
enable to degrade bacterial
exopolysaccharide matrix. The quantitative measurements of colistin diffusion through biofilm and
antibiotic concentration in biofilm after phage application were measured by
laser interferometry system. It consisted of a Mach-Zehnder interferometer with
He-Ne laser, membrane elements (place of biofilm formation), TV-CCD camera and software
for interference images acquisition and processing. The interferograms were recorded from 120 to 2400 s
with a time interval of Δt
= 120 s and the profiles for colistin were constructed. Profiles served
for calculation of the colistin amount transported through biofilm in function
of time (N(t)). In the same assay the amount of colistin distributed in biofilm
was determined. The level of P.
aeruginosa biofilms eradication by bacteriophages and/or colistin were determined
by microscopic pictures analysis after crystal violet or methylene
blue staining using
imageJ software.
This work was supported by grant 2012/04/M/NZ6/00335 from the National Science Centre,
Poland. Michal Arabski
and Zuzanna Drulis-Kawa acknowledge COST Action BM1003 "Microbial cell
surface determinants of virulence as targets for new therapeutics in Cystic
Fibrosis".
