There have been reports on infections associated with the use of inadequately disinfected fibreoptic instruments; Salmonella infections were described by Burkhardt (1976), Dean (1977), and Schliessler et al. (1980), Pseudomonas infections by Greene et al. (1974), Noy et al. (1977), and Ansink-Schipper et al. (1981).
In spite of improvement in disinfection and sterilization procedures, disinfection of endoscopes has remained a problem. The instruments cannot be autoclaved at the usual temperature. Ethyleneoxide sterilisation, though effective, takes too long. Disinfection by recommended disinfectants such as 2~ aqueous glutaraldehyde is difficult because of the numerous and complicated channels in the instrument.
We were asked to check the disinfecting capacity of a commercial endoscope washing machine, before it was to be put on the market.
A colonoscope was used as the test instrument. This endoscope is technically complicated for, in addition to a biopsy channel, there are three other channels (for water, air and CO2) which end in one common channel at the distal part. The washing machine has connections only for disinfection of the biopsy and water channel. There are reservoirs for the detergent solution used and for the disinfectant (2~ glutaraldehyde), respectively. The detergent is discarded after use. The disinfectant is used in a recirculation system. Between the detergent and disinfectant cycle there is a water rinse for 3 minutes and at the end of the process air is blown through the channels for 10 seconds.
Several series of disinfection experiments were performed after contamination of the colonoscope with Serratia marceseens, either at the handling site or at the distal end. After the cleaning, disinfection and rinsing procedures, samples were taken from ten different sites and cultured.
When used according to the instructions no proper disinfection could be achieved except for the biopsy channel. The causes for the malfunction proved to be threefold: 1. use of less and less detergent after a few cycles, 2. dilution of the glutaraldehyde solution, to rapidly decreasing concentrations, down to 1% or less, by the rinsing procedures, 3. lack of disinfection of the air and CO2 channels.
Subsequently, an attempt was made to achieve proper disinfection by using fresh glutaraldehyde and detergent at every cycle; in addition, the air and CO2 channels were also cleaned and disinfected by means of a special connection constructed for these channels. These latter connections were of a makeshift nature and could not be completely machine-operated.
With these adaptations almost all samples taken for testing bacterial contamination were negative, indicating that with the proper technical adaptation this washing machine could be effective.
When considering the purchase and use of a programmed endoscope-washing machine, particular attention should be given to constant concentration of the disinfectant, to adaequate rinsing and to proper drying procedures. However, most important is that proper disinfection can only be achieved if all channels, including air and CO2 channels, are included in the rinsing and disinfection procedures.