Effectiveness of detergent-disinfecting agents on Escherichia coli 54127 biofilm

Detergent-disinfecting agents (dD) are used daily for cleaning reused medical devices. We have devised a simple method to test dD detergent activity (DA) using an E. coli 54127 biofilm prepared in haemolysis glass tubes, which are cleaned with test dD, according to supplier's recommendations. Crystal violet 0.05% is used to colour the residual biofilm after dD (or tap water control) application. The biofilm quantification was made indirectly by measuring the absorbance of crystal violet at 585 nm. A measure of the detergent effectiveness called DA was calculated as the percentage reduction of colour from a tap water control. Fifteen products including enzymatic and non-enzymatic dDs were evaluated. Most enzymatic dDs gave a high DA, as did some non-enzymatic products. Thus, the view that enzymatic dDs are more effective than non-enzymatic dDs, put forward by some manufacturers, should be regarded with caution. The DA determination should help infection control teams choose, within the wide range of products available on the market, the most effective dD based on both its detergent and disinfecting activity.