Bacterial propagation in reusable water reservoirs in a humidified oxygen supply system

Bacterial colony counts in reusable water reservoirs in a humidified oxygen supply system maintained only by the addition of nonsterilized water, with or without washing (conventional procedure), were examined. Bacteria were detected in all the reservoirs even before the operation of the oxygen suppliers, and colony counts of more than 1 x 10(2)/ml of bacteria were detected in some reservoirs without washing. Many bacteria were also detected in many reservoirs, after the operation of the oxygen suppliers, indicating that bacteria had contaminated the water reservoirs and propagated during this operation. These results suggest that it is not recommended to maintain these water reservoirs by the conventional procedure.