Mojtaba Anvarinejad - Prof. Alborzi Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
Pejman Abbasi - Prof. Alborzi Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
Gholamreza Pouladfar - Prof. Alborzi Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
Zahra Jafarpour - Prof. Alborzi Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran

Background and Objectives: Blood stream infections cause significant morbidity and mortality in patients, especially in developing countries. Changing the epidemiological pattern of microorganisms as well as the growing trend of antibacterial resistance makes it an important health problem in Iran. The aims of this study were to evaluate the spectrum of pathogens causing BSI’s in hospitalized patients in Shiraz (Iran), as well as their antimicrobial resistance patterns. Materials and Methods: In this retrospective study, 1404 positive blood samples were analyzed in one- year period from March 2018 to March 2019. Samples from Namazi hospital were transferred to Professor Alborzi Clinical Microbiology Center. The isolates were characterized by conventional API, biochemical tests and then were tested for susceptibility to 24 different antibiotics using the disk diffusion method. Susceptibility patterns were established consistent with CLSI recommendations. Results: Stenotrophomonas maltophilia (36.5%), Staphylococcus aureus (7.7%), E.coli (7.6%), Enterococcus spp. (5.6%) were the most common pathogenic bacteria isolated from the blood cultures. Linezolid and vancomycin had the highest effectiveness against gram positive bacteria and gram negative bacteria had high sensitivity to polymyxin B and colistin. Conclusion: Due to increasing antimicrobial resistance, regular microbiological and clinical surveillance of blood stream infections in hospital is required to inform appropriate antibiotic protocols and monitor the impact of infection prevention strategies.