Effects of ampicillin on intracellular levels of adenosine triphosphate in bacterial cultures related to antibiotic susceptibility.

Short time effects of ampicillin on viability and levels of intracellular ATP were studied in bacterial cultures and a close relationship between intracellular ATP levels and viability was demonstrated. The connection between the effects observed and MIC values is discussed. The possibility of using the phenomenon for rapid antibioitc susceptibility testing was studied in clinical isolates incubated for 2 hours followed by luciferase assay of intracellular ATP. A positive correlation was demonstrated between ampicillin-induced decreases in intracellular ATP and inhibitory zone diameters, as measured by the agar diffusion technique.