An evaluation of the use of chlorine dioxide (Tristel One-Shot) in an automated washer/disinfector (Medivator) fitted with a chlorine dioxide generator for decontamination of flexible endoscopes

Microbiological tests were carried out to evaluate a new chlorine dioxide s terilant: Tristel One-Shot. Preliminary in vitro suspension tests showed th at solutions containing around 140 ppm chlorine dioxide achieved a reductio n factor exceeding 10(6) of Staphylococcus aureus in 1 min and of Bacillus subtilis spores in 2.5 min in the presence of 3 g/L bovine albumin. Subsequ ent tests evaluated the effectiveness of Tristel One-Shot in a Medivator wa sher/ disinfector fitted with a Tristel Generator for processing flexible e ndoscopes. Each test run involved three stages. In the first, the instrumen t and air-water channels of a gastroscope were inoculated with a suspension of Pseudomonas aeruginosa (10(8) cfu/ml) in 10% sodium glutamate and serum (0, 5 or 10%) and then drained, partially dried, and saline flushed throug h for total viable counts (TVCs). In the second stage, the channels were re -inoculated with test organisms; detergent was flushed through the channels which were then brushed; and saline was flushed through for TVCs. In the t hird stage, the channels were re-inoculated; detergent was flushed through the channels which were then brushed; the endoscope was processed in the Me divator; and saline was flushed through for TVCs. Carrying out all three st ages enabled determination of (1) the contribution played by manual cleanin g of channels prior to processing in the Medivator, and (2) the combined ef fect of manual cleaning followed by processing. Two series of test runs wer e done. In the first, the Tristel Generator was set to generate 230 ppm chl orine dioxide, and in the second 150 ppm. In the first, cleaning followed b y processing in the Medivator consistently achieved a >10(6)-fold reduction of test organisms, and in the second a >10(5)-fold reduction. Pre-cleaning of channels was very important-when done the initial concentration of seru m in the inoculum (0-10%) had no affect on the results obtained after proce ssing. (C) 200 1 The Hospital Infection Society.