In-vitro effect of doxycycline on levels of adenosine triphosphate in bacterial cultures. Possible clinical applications.

Short-term effects of doxycycline on viability and levels of intracellular ATP in bacteria were studied. Inhibition of growth by doxycycline was reflected in a corresponding inhibition of the accumulation of intracellular ATP which was clearly demonstrable within 1-2 hours. The effects of doxycycline on intracellular ATP were dose-dependent and the use of ATP assays for quantitation of antibiotics in serum is discussed. In 45 clinical isolates exposed to doxycycline a positive correlation was found between antibiotic-induced inhibition of intracellular ATP levels and inhibitory zone diameters with the disc diffusion method, indicating possible clinical applications in rapid susceptibility testing.