| ironjustice@aol.com 2006-03-22, 3:40 pm |
| Chelator-Induced Dispersal and Killing of Pseudomonas aeruginosa Cells
in a Biofilm.
Banin E, Brady KM, Greenberg EP
Appl Environ Microbiol. 2006 Mar ; 72(3): 2064-9
Biofilms consist of groups of bacteria attached to surfaces and encased
in a hydrated polymeric matrix. Bacteria in biofilms are more resistant
to the immune system and to antibiotics than their free-living
planktonic counterparts. Thus, biofilm-related infections are
persistent and often show recurrent symptoms. The metal chelator EDTA
is known to have activity against biofilms of gram-positive bacteria
such as Staphylococcus aureus. EDTA can also kill planktonic cells of
Proteobacteria like Pseudomonas aeruginosa. In this study we
demonstrate that EDTA is a potent P. aeruginosa biofilm disrupter. In
Tris buffer, EDTA treatment of P. aeruginosa biofilms results in
1,000-fold greater killing than treatment with the P. aeruginosa
antibiotic gentamicin. Furthermore, a combination of EDTA and
gentamicin results in complete killing of biofilm cells. P. aeruginosa
biofilms can form structured mushroom-like entities when grown under
flow on a glass surface. Time lapse confocal scanning laser microscopy
shows that EDTA causes a dispersal of P. aeruginosa cells from biofilms
and killing of biofilm cells within the mushroom-like structures. An
examination of the influence of several divalent cations on the
antibiofilm activity of EDTA indicates that magnesium, calcium, and
iron protect P. aeruginosa biofilms against EDTA treatment. Our results
are consistent with a mechanism whereby EDTA causes detachment and
killing of biofilm cells.
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