Study of Imipenem and Colistin resistance rates of isolated Acinetobacter baumannii from hospitalized patients in Imam Reza and Ghaem hospitals of Mashhad through E-test

Introduction: Acinetobacter baumannii is one of the primary causes of nosocomial infections. Furthermore, the increment of antibiotic resistance has raised concerns about the proper therapeutic approach to this problem. This study aimed to determine the susceptibility of A.baumannii to colistin and imipenem through minimal inhibitory concentration (MIC). Methods: In this study, 2745 samples (2745 plate) were collected from patients in different wards of Ghaem Hospital and Imam Reza Hospital in Mashhad between October 2015 and September 2016. In the case of a specimen was wound, after disinfection of the wound surface using a sterile swab from the inferior part of the sample, middle stream urine was collected in sterile container, and the bronchial specimen was taken by the doctor by syringe. In this study, 100 A.baumannii were isolated from 100 hospitalized patients at Imam Reza and Ghaem hospitals of Mashhad, By Biochemical tests (Kligler iron agar, Lysine, urea indole) diagnostic and then disc diffusion method, and E-test strips were utilized to evaluate infection, antibiotic susceptibility, and MIC, respectively. .Results: The obtained results of disc diffusion showed that all isolates were resistant to imipenem, which was also confirmed by E-test strips. Moreover, all isolates were sensitive to colistin. The obtained colistin MIC was 0.25μg/ml for one sample and ≤2μg/ml for others; which were considered sensitive according to the Clinical and Laboratory Standards Institute standards. Conclusion: The high resistance of A.baumannii to imipenem was indicative of resistance pattern changes of this bacteria and insufficiency of the mentioned antibiotic for treatment. However, colistin is still effective and should be prescribed more carefully to prevent resistant strains spread.