Enterococcus faecalis and Pseudomonas aeruginosa were used to develop biofilm over 8 days. The biofilm on each minimum biofilm eradication concentration peg contained 8 log10 colony forming units (CFU)/cm2 of both bacteria. The detergents evaluated were as follows: Prolystica Enzymatic 2X, Prolystica Neutral 2X, Neodisher, and Endozime Bio-Clean. The disinfectants evaluated were as follows: glutaraldehyde, accelerated hydrogen peroxide, and ortho-phthalaldehyde. Biofilm removal was evaluated using viable count, protein and carbohydrate quantitation, and scanning electron microscopy.
Only Prolystica Enzymatic 2X and Endozime Bio-Clean killed both E faecalis (3.90 log10 CFU/mL reduction) and P aeruginosa (3.96 log10 CFU/mL reduction) in suspension. None of the detergents tested could provide >1 log10 CFU/cm2 reduction for bacteria within biofilm. Any combination of detergent and high-level disinfectant reduced the level of both E faecalis and P aeruginosa within biofilm by 3-5 log10 CFU/cm2. Although the combination of Endozime Bio-Clean and glutaraldehyde provided a 6 log10 reduction, it could not eliminate both bacteria within biofilm.
Our data indicate that if biofilm accumulates in flexible endoscope channels during repeated rounds of reprocessing, then neither the detergent nor high-level disinfectant will provide the expected level of bacterial removal or killing.