Evaluation of Rodent Cage Processing Using Reduced Water Temperatures

Studies published in 1994 and 2000 established a temperature range of 143-180 °F for effective cage sanitization in animal facilities. These 2 studies were, respectively, theoretical and based on experiments using hot water to sanitize bacteria-coated test tubes. However, such experimental methods may not capture the practical advantages of modern washing technology or account for the routine use of detergent in cage wash. Moreover, these methods may not translate to the challenges of removing adhered debris and animal waste from the surfaces being sanitized. A sample of highly soiled cage bottoms, half of which were autoclaved with bedding to create challenging cleaning conditions, were processed at 6 combinations of wash and rinse cycles with 125 °F, 140 °F, and 180 °F water with detergent. All cycles were equipped with a data logging device to independently verify temperatures. After washing, cages underwent visual inspection and microbial sampling consisting of organic material detection using ATP detection and Replicate Organism Detection and Counting (RODAC) plates. Cages with any amount of visible debris failed inspection, as did cages that exceeded institutional sanitization thresholds. Results indicate that wash and rinse temperatures of 140 °F for a programmed wash duration of 450 s and rinse of 50 s effectively clean and disinfect both highly soiled and autoclaved cages. Accounting for both steam and electrical energy, these parameters result in an annual savings of $21,867.08 per washer on an equivalent run basis using the current institutional standard of 180 °F.