Razieh Amirfakhrian - Antimicrobial Resistance Research Center, Buali Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran.
Atieh Yaghobi - Antimicrobial Resistance Research Center, Buali Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran.
Roya Saddat Ghaderi - Antimicrobial Resistance Research Center, Buali Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran.
Seyed Isaac Hashemy - Surgical Oncology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
Kiarash Ghazvini - Department of Microbiology and Virology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran

Introduction: In recent decades, the inappropriate use of antibiotics and the existence of transferable resistant elements have caused the emergence of multidrug-resistant (MDR) gram-negative organisms. Antimicrobial resistance is becoming one of the major challenges to public health and has caused morbidity and mortality worldwide. The purpose of this study was the assessment of the prevalence and frequency of colistin resistance among gram-negative bacilli (Enterobacteriaceae, Acinetobacter spp., and Pseudomonas spp.) in Iran and around the world. Methods: For this systematic review and meta-analysis, we searched international and national databases, including PubMed, Google Scholar, SID, and Magiran, from 1998 to 2018 for articles and abstracts describing colistin resistance among gram-negative bacilli. We have included 92 studies that met our inclusion criteria, and the outcomes were combined using a random-effects model to derive the event rate of colistin resistance among gram-negative bacilli. Data were analyzed by the Comprehensive Meta-Analysis Software (V2), and the heterogeneity of the studies was assessed using the I2 index. Results: Out of the 11050 papers identified, 92 studies met the strict inclusion criteria and were finally included. The overall event rate of colistin resistance among gram-negative bacilli (GNB) was about 6.6%, while the event rate of colistin resistance among Acinetobacter spp. (n = 18504) was 2.8% (summary: 95% confidence interval (CI): [0.02, 0.041], P = 0.001, I2 = 70, df (Q) = 36, Q-value = 121.924). The colistin resistance among Pseudomonas spp. (n = 15094) was 3% (95% CI: [0.022, 0.041], P = 0.001, I2 = 68.3, df (Q) = 25, Q-value = 85.648), and the colistin resistance among Enterobacteriaceae spp. (n = 44772) was 0.8% (95% CI: [0.004, 0.014], P = 0.001, I2 = 87.6, df (Q) = 15, Q-value = 71.291). Therefore, the event rate of resistance to colistin among GNB was relatively low (6.6%). Conclusion: The event rate of resistance to colistin among GNB was low. Therefore, this antimicrobial agent can still be administered as a suitable option against GNB that are resistant to other antibiotics such as carbapenems.

Acinetobacter spp, Enterobacteriaceae, Colistin, gram-negative rods, Iran, Prevalence, Pseudomonas spp, Resistance