Developing a reproducible assay for the detection of biofilm removal

Abstract

Biofilm is a colony of microorganisms that grow together in a structure which improves survival. In the healthcare setting, biofilm can form on chronic wounds and more readily in immunocompromised patients. It is also more likely to form on foreign materials placed within the human body for therapeutic reasons and on inadequately processed medical devices used for diagnostic or surgical reasons. The detection and elimination of these biofilms poses challenges for healthcare professionals and those involved in the cleaning of medical devices. Pseudomonas aeruginosa was grown on plastic coupons in the CDC bioreactor. The protein assay and the crystal violet assay were used to develop a method of detecting the efficacy of detergents to remove biofilm from these plastic coupons. Whether protein assay or crystal violet assays were used, similar results were obtained. Similar results were also obtained regardless of coupon or rod position. Results of biofilm removal were confirmed with confocal laser scanning and scanning electron microscope images obtained of the coupons. Some commercial medical device products were then tested. Zen and RMEC were selected as being representative of enzymatic cleaners and were found to be efficient cleaners. Matrix and Tween were selected as detergents, and were found to be less efficient cleaners. Two concentrations of NaOH at differing temperatures and contact time were also tested as possible standards against which industry could compare their products.. The protein assay was selected to test a range of hard surface cleaners. NaOH 0.4% at 700C for 5 mins was tested as a standard. Both 1% and 0.1% bleach (oxidising agent) were found to be efficient cleaners. Benzalkonium chloride (quaternary surfactant) was found to be a reasonable cleaner whereas acetic acid and 0.01% bleach were found to be inefficient cleaners. It is hoped that this research encourages the introduction of a standard of biofilm removal with which cleaners can comply. This would bring the cleaners industry in line with standards used to test sterilants and disinfectants.