S154c: Development and Control of Bacterial Biofilms

In order to monitor the development and control of biofilms formed by Pseudomonas aeruginosa and Staphylococcus aureus, stainless steel disks were exposed to spectrophotometrically calibrated inocula in growth chambers containing nutrient broth. For each experiment sterile growth chambers were processed as controls and inoculated growth chambers were processed to determine initial populations. The remaining growth chambers were incubated at 37o C and 135 rpm for 24 hours. Growth chambers were then processed to provide final populations and were exposed to varying concentrations of phenol (0.5% to 5.0% w/v) for 15 minutes. The process used for the growth chambers included rinsing disks in sterile isotonic saline to remove unattached organisms, scraping the disks with rubber policemen to remove sessile organisms, diluting, and spread plating the scrapings. Nutrient broth samples were also diluted and spread plated. The process was repeated with the inclusion of 15 minute exposures to phenol. For all experiments duplicate growth chambers were processed and duplicate plates were made. Both organisms were consistently retrieved from the untreated disks and nutrient broth samples indicating supportive growth conditions and the biofilm formation capabilities of the organisms. The counts of planktonic organisms exposed to phenol indicted all concentrations of phenol above 0.5% by weight were able to reduce bacterial populations by 99.99%. The counts of sessile organisms indicated concentrations above 3.0% by weight were able to reduce bacterial populations by 99.99%; the results indicated that significant increases in concentration of phenol are required to control organisms protected by biofilms.