ATP bioluminescence assay for fapid antibacterial susceptibility testing.

We studied adenosine triphosphate (ATP) synthesized by bacteria in tube dilution cultures to devise a rapid antibacterial susceptibility test. The ATP level was determined with a firefly (Photinus pyralis) luciferin/luciferase bioluminescence assay, which allows a direct quantifying of bacteria above 10,000 CFU/ml. At sub-MIC, total bacterial ATP levels were paralleled by increased viable bacterial counts. At above MIC, however, total bacterial ATP levels remained almost constant or decreased gradually. Large differen in total ATP level were observed between sub-and above-MIC levels in the overnight cultures. These differences were also observed in cultures at 6 h. This method may be utilized for rapid antibiotic susceptibility testing.