EVALUATION AND USE OF A LOW NUTRIENT MEDIUM AND REDUCED INCUBATION-TEMPERATURE TO STUDY BACTERIAL-CONTAMINATION IN THE WATER-SUPPLY OF DENTAL UNITS

A low nutrient medium, dilute peptone, and reduced incubation temperat ures (25 or 30 degrees C) were used to recover bacteria from dental un it water supply. Significantly greater numbers of bacterial colony-for ming units were recovered on the dilute peptone medium than on the enr iched media, blood agar or trypticase soy agar. Lower incubation tempe ratures yielded greater numbers of colony-forming units on all media. The bacterial population in dental unit water supply following stagnat ion in the supply lines and flushing of the lines was studied using di lute peptone incubated at 25 degrees C. No significant differences in the numbers of colony-forming units were found in stagnant water versu s fresh water. Flushing the water lines for 10 min did not significant ly reduce the numbers of colony-forming units.