In vitro evaluation of minimum inhibitory concentration of several antibacterial agents against Rickettsia japonica using a plaque reduction assay system

Abstract The study was conducted to determine the minimum inhibitory concentrations (MICs) of several antibacterial agents against Rickettsia japonica , which causes Japanese spotted fever. A plaque reduction assay as an in vitro culture method was conducted to determine the MICs of antibacterial agents (4 types of tetracyclines: tetracycline, doxycycline, minocycline, and tigecycline; 3 types of quinolones: ciprofloxacin, ofloxacin, and levofloxacin; and 2 types of macrolides: azithromycin and clarythromycin) against R. japonica . R. japonica was sensitive to the antibacterial agents tested with MICs similar to those against other spotted fever rickettsia determined in previously described plaque reduction assays.