RESUMEN
Resistance patterns among nosocomial bacterial pathogens in hospitals may vary widely from country to country at any given point and within the same country over time. Acinetobacter baumannii is one of the most important bacterium causes hospital acquired infections. Therefore, surveillance of antibiotic resistance of A. baumannii is necessary, especially in our country which there is no have much data in this field. In a prospective study, strain comprised of a total of 191 recent clinical isolates selected consecutively from clinical infections of separate patients from three University hospitals in Tehran. Minimum inhibitory concentration [MIC] of these organisms for imipenem, ciprofloxacin and ceftazidime was determined using E test method according to CLSI guideline. Also, MIC50 and MIC90 percent was calculated for each of these antibiotics. The percentages of Acinetobacter baumannii isolates susceptible to ciprofloxacin and ceftazidime by E test were 55.5% and 44.5%, respectively. The percentage of bacterium susceptible to imipenem by E test was 72.8%. MIC50 and MIC90 of imipenem in E test were 1.5 and > 32, respectively. High antimicrobial resistance against A. baumannii species has been seen in Iran; therefore, it is necessary to implement some approaches for prevention of bacterial spread