COMPARISON OF RESPIRATORY ACTIVITY AND CULTURABILITY DURING MONOCHLORAMINE DISINFECTION OF BINARY POPULATION BIOFILMS

Biofilm bacteria challenged with monochloramine retained significant r espiratory activity, even though they could not be cultured on agar pl ates. Microbial colony counts on agar media declined by approximately 99.9% after 1 h of disinfection, whereas the number of bacteria staine d by a fluorescent redox dye experienced a 93% reduction. Integrated m easures of biofilm respiratory activity, including net oxygen and gluc ose utilization rates, showed only a 10 to 15% reduction. In this biof ilm system, measures of microbial respiratory activity and culturabili ty yielded widely differing estimates of biocide efficacy.