Effects of chelating agent and environmental stresses on microbial biofilms: relevance to clinical microbiology.

Aims:ÔÇé To determine the effect of pH, temperature, desiccation, ethylenediaminetetraacetic acid (EDTA) and Desferrioxamine B (DFO) on Panton-Valentine Leukocidin positive Community Acquired MethicillinÔÇâSusceptible Staphylococcus aureus (PVL +ve CA-MSSA) biofilm formation. Methods and Results:ÔÇé Biofilms from PVL +ve CA-MSSA (clinical isolate) were subjected to pH, temperature, desiccation, EDTA and DFO. PVL +ve CA-MSSA were more resistant to pH and heat than their planktonic equivalents. Desiccation studies demonstrated that PVL +ve CA-MSSA biofilms were more refractory to the treatment than planktonic cells. Significant inhibition of PVL +ve CA-MSSA biofilm formation was observed in the presence of 1 mM EDTA. Low concentrations (2.5 μM) of DFO enhanced the growth of PVL +ve CA-MSSA biofilms. At higher concentrations (1 mM) DFO did inhibit the growth but not as much as EDTA. A combination of EDTA and DFO inhibited PVL +ve CA-MSSA biofilm formation at lower concentrations than either alone. Conclusions:ÔÇé This study demonstrates that PVL +ve CA-MSSA biofilms are resistant to environmental stress but their growth can inhibited effectively by a mixture of EDTA and DFO. Significance and Impact of Study:ÔÇé The inhibition of biofilm formation by PVL +ve CA-MSSA using chelating agents has not been previously reported and provides a practical approach to achieve the disruption of these potentially important biofilms formed by an emerging pathogen.