The aim of this study was to evaluate the antimicrobial activities of Trachyspermum ammi, essential oil against different kinds of microorganisms by microtiter plate method. All 36 isolates of (12 Klebsiella pneumoniae, 12 E.coli and 12 Staphylococcus aureus) isolated from urine culture of hospitalized patients(Amir Al-Momenin Hospital, Zabol, south-eastern Iran) suffered from urinary tract infections were evaluated. In this study, the essential oil of Trachyspermum ammi
obtained by hydrodistillation for 2.5-3 h using a Clevenger-type apparatus and the minimum inhibitory concentrations were determined tocharacterize the antimicrobial activities of this essential oil. The results showed E. coli isolates were resistance to 4 of the antibiotics including ceftazidime (50%) cefixime (41.6%), tetracyclin(75%), erythromycin(58.3%). However k. pneumonia isolates were resistance to 3 of the agent includingceftazidime(33.3%) ,cefixime(58.3%), erythromycin(75%) and S.aureus isolates were resistance to 6 of the agent including cefixime (33.3%), trimethoprim-sulfamethoxazol(41.66%), penicillin(50%), oxacillin(3.3%), ceftazidime(66.6%) and vancomycin(8.3%) and the MIC value was also determined against all the tested bacteria. The highest MIC values of essential oil were determined 100ppm against E. coli and highest MIC value for K.pneumoniae was 250ppm. In conclusion, it seems that Trachyspermum ammi
essential oil could inhibit the growth of all of the tested bacteria.