A novel polytetrafluoroethylene-channel model, which simulates low levels of culturable bacteria in buildup biofilm after repeated endoscope reprocessing.

BACKGROUND AND AIMS: Clinical studies have shown variable culture results from flexible endoscope channels possibly because of low levels of bacteria that are difficult to extract. The aim of this study was to develop a simulated-use buildup biofilm (BBF) model that mimics low levels of viable bacteria after repeated rounds of aldehyde fixation and accumulation. METHODS: New endoscope channels were exposed to 8 days of repeated rounds of biofilm formation using ATS2015 containing Enterococcus faecalis and Pseudomonas aeruginosa, rinsing, fixation with glutaraldehyde, and rinsing. Viable count and scanning electron microscopy and borescope examination were used to compare the impact of dry storage over 26 weeks on the level of culturable bacteria and to compare the Centers for Disease Control and Prevention flush method of channel harvesting with a flush-brush-flush method. RESULTS: E faecalis (log10 6.6) and P aeruginosa (log10 8.6) accumulated over 8 days of cyclic biofilm formation and partial glutaraldehyde fixation, but after a final exposure to 2.6% glutaraldehyde the level of culturable bacteria was less than 2 log10. The Centers for Disease Control and Prevention channel harvesting method appeared by borescope to be inferior to a flush-brush-flush sample collection method for detection of viable bacteria. P aeruginosa increased up to 7 log10 after 26 weeks of dry storage, indicating there were viable but nonculturable bacteria present initially that recovered during storage. CONCLUSIONS: Viable but nonculturable P aeruginosa within the BBF model are able to recover, and this phenomenon may explain the variability of culture in patient-used endoscopes. Our data also indicated that friction may be a critical part of sample collection from endoscope channels.

A new buildup biofilm model that mimics accumulation of material in flexible endoscope channels.

The objective of this study was to develop a new build up biofilm (BBF) model that was based on repeated exposure to test soil containing Enterococcus faecalis and Pseudomonas aeruginosa and repeated rounds of fixation to mimic the accumulation of patient material in endoscope channels during reprocessing. The new BBF model is a novel adaptation of the minimum biofilm effective concentration (MBEC) 96-well model where biofilm is formed on plastic pegs. The new MBEC-BBF model was developed over eight days and included four rounds of partial fixation using glutaraldehyde. There was 6.14Log10cfu/cm(2) of E. faecalis and 7.71Log10cfu/cm(2) of P. aeruginosa in the final BBF. Four detergents (two enzymatic and two non-enzymatic) were tested alone or in combination with orthophthalaldehyde, glutaraldehyde or accelerated hydrogen peroxide to determine if BBF could be either removed or the bacteria within the BBF killed. None of the detergents alone could remove the biofilm or reduce the bacterial level in the BBF as determined by viable count and scanning electron microscopy. The combination of detergents and disinfectants tested provided a 3 to 5Log10 reduction in viable bacteria but no combination could provide the expected 6Log10 reduction. Our data indicated that once formed BBF was extremely difficult to eliminate. Future research using the BBF model may help develop new cleaning and disinfection methods that can prevent or eliminate BBF within endoscope channels.

Evaluation of the ability of different detergents and disinfectants to remove and kill organisms in traditional biofilm.

BACKGROUND: The objective of this study was to assess the ability of different detergent and disinfectant combinations to eradicate bacteria in traditional biofilm. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.