The in-vitro anti-rickettsial activity of macrolides.

The anti-rickettsial activity of azithromycin and clarithromycin was studied in Vero cells. The rate of rickettsial inhibition-growth caused by both macrolides was determined using rickettsial counts and ELISA. Both macrolides inhibited > 50% the growth of Rickettsia conorii and Rickettsia typhi at concentrations of 1.0 and 0.1 mg/L, respectively. The growth of Coxiella burnetii was inhibited to a rate of > or = 50% at the concentrations of 0.01 and 1.0 mg/L of azithromycin and clarithromycin, respectively.