Inactivation of Pseudomonas aeruginosa Biofilms by Gas Discharge Plasma

ZELAYA, A., LWIN, S., STOUGH, G., RAD, N., VANDERVOORT, K., AND BRELLES-MARIÑO, G.

San Diego, California, Estados Unidos de America

Congreso; American Society for Microbiology (ASM) 110th. General Meeting; 2010

American Society for Microbiology

Biofilms are microbial communities responsible for undesirable effects such as disease and biofouling. Conventional methods of controlling microbial growth are often ineffective with these hard-to-destroy communities. Therefore, there is a need to develop new sterilization techniques. The use of gas discharge plasmas is an alternative since plasmas contain a mixture of reactive species, free radicals, and UV photons which decontamination potential relative to free microorganisms is well established. We have reported the use of plasma to inactivate C. violaceum biofilms (Joaquin et al., 2009). We are presently studying biofilm inactivation in the opportunistic pathogen Pseudomonas aeruginosa PA01.   One, 3, and 7 day-old biofilms were produced in batch culture using the CDC biofilm reactor (BioSurface Tech., MT). The biofilms were grown on polycarbonate, stainless-steel, and borosilicate coupons. An atmospheric pressure plasma jet was generated with an AtomfloTM 250 reactor (Surfx Tech., CA) using a mixture of He and N2 gases. After removing planktonic cells, biofilms were exposed to plasma for various exposure times, scrapped off the coupons, and processed to determine CFUs/mL after incubation. For atomic force microscopy (AFM) experiments, coupons were rinsed twice and air-dried. Images were collected in air in intermittent contact mode with a Quesant microscope. Our data show almost 100% of cell removal after a 5-minute plasma treatment. The inactivation kinetics is similar for 1, 3, and 7 day-old biofilms and shows a rapid decline in the number of surviving cells followed by a much slower decline. Cell concentration for the control is two log units higher for 3 day-old biofilms compared to 7 day-old ones, suggesting that the attachment is time-dependent and decreases after reaching a peak. No differences were observed for the 3 materials used. AFM images show changes in cell morphology and biofilm structure for various plasma exposure times and we are presently studying micromechanical properties of the biofilms through force versus distance curves. Results indicate the potential of plasma as an alternative way for biofilm removal.