The Combined Effects of Physical Removal, Proper Cleaner Selection and Sanitizer on the Reduction of a Pseudomonas aeruginosa Biofilm

Introduction: Many studies on biofilm treatments have investigated the efficacy of sanitizers alone. In order to fully understand the dynamics involved in the reduction of biofilm from surfaces, we examined the effects of physical removal, cleaner selection and use of a peracid based sanitizer alone and in combination.

Purpose: This study was performed to examine the combined effects of physical removal, cleaner selection and sanitizers on the reduction of a Pseudomonas biofilm.

Methods: A Pseudomonas aeruginosa (ATCC 15442) biofilm was grown in a CDC Biofilm reactor on 304 stainless steel carriers following methodology adapted from the ASTM E2562 standard. Biofilm coated carriers were exposed to various treatment combinations consisting of physical removal (PR), a non-chlorinated alkaline cleaner (NC-AC), a chlorinated alkaline cleaner (C-AC) and a peracid sanitizer. Following exposure, carriers were neutralized, biofilm disaggregated via a series of vortex/sonication steps and survivors enumerated by serial dilution and plating onto Tryptic Soy Agar + 5% Sheep’s Blood. Log survivors were calculated for comparison of each treatment combination.

Results:  Data demonstrates that the additive effects of PR, cleaners and sanitizers are significantly different (p<0.05) then each of the treatments alone. PR provided < 0.5 log reduction, the cleaners + PR from 0.5 to 4.0 log reduction and the sanitizer alone a 1.0 log reduction. From least effective to most effective: PR < NC-AC +PR < sanitizer < sanitizer + PR < NC-AC + PR + sanitizer < C-AC + PR < C-AC + PR+ sanitizer.

Significance:  This study verifies that the performance of a full cleaning process with appropriate cleaner selection is essential for effective management of biofilms.