RESUMEN
Bloodstream infection [BSI] is an important cause of mortality and morbidity and among the most common health-care associated infections. In this study we described the frequency of occurrence and antimicrobial susceptibility patterns of nosocomial and community-acquired BSI isolates from a teaching hospital in Tehran, Iran. his cross-sectional study was conducted in 850-bed Rasul Akram university hospital from April 2006 to April 2007. All patients with a positive blood culture were enrolled. Antimicrobial susceptibility testing was performed with disk diffusion and E-test MIC. During the study period, 456 isolates were obtained from blood cultures, from a total of 8818 collected sets, among which 291 were felt to represent true bacteremia and 98 were nosocomial. Acinetobacter spp. were the most frequently isolated agents in the hospital and community acquired BSIs [32%], followed by Escherichia coli [13.7%] and Klebsiella spp. [12%]. The most effective antibiotics for gram-negative and gram-positive bacteria were ciprofloxacin [13% resistance rate] and vancomycin and oxacillin [with 13% resistance rate], respectively. Analysis of antibiotic resistance pattern showed that 20.43% of Acinetobacter spp. and 15.4% of Pseudomonas aeruginosa were multi drug resistant [MDR], while 48.7% of Kiebsiella spp were ESBL-producing isolates and 15% of Staphylococcus aureus were oxacillin-resistant. We did not observe any vancomycin-resistant strains among isolates of S. aureus. Rifampin and ciprofloxacin showed good activity against most of gram-positive and gram-negative organisms, respectively. Carbapenems [imipenem and meropenem] were highly active against strains of Enterobacteriaceae [E. coli, Klebsiella] that showed resistance to third generation of cephalosporines