Prevalence of antibiotic resistance in Escherichia coli strains simultaneously isolated from humans, animals, food, and the environment: a systematic review and meta-analysis Ali Pormohammad,1 Mohammad Javad Nasiri,2 Taher Azimi2,31Student Research Committee, Department of Microbiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; 2Department of Microbiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; 3Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, IranBackground: Antimicrobial resistance is a serious public health problem worldwide. We aimed to investigate the prevalence of antibiotic resistance in Escherichia coli strains simultaneously isolated from humans, animals, food, and the environment.Methods: Studies on PubMed, Embase, and the Cochrane Library published from January 1, 2000 to January 1, 2018 were searched. The quality of the included studies was assessed by the modified critical appraisal checklist recommended by the Joanna Briggs Institute. All analyses were conducted using Biostat’s Comprehensive Meta-Analysis version 2.0. Depending on the heterogeneity test for each antibiotic, we used a random- or fixed-effect model for pooled prevalence of drug resistance. Studies were eligible if they had investigated and reported resistance in two or more isolation sources (human, animal, food, or environment). To decrease heterogeneity and bias, we excluded studies that had reported E. coli drug resistance isolated from one source only. We included publications that reported drug resistance with minimum inhibitory concentration or disk diffusion method (DDM) as antibiotic-susceptibility tests.Results: Of the 39 included studies, 20 used the DDM and 19 minimum inhibitory concentration for their antibiotic-susceptibility testing. Colistin had the lowest prevalence, with 0.8% (95% CI 0.2%–3.8%) and amoxicillin the highest, with 70.5% (95% CI 57.5%–81%) in isolated human E. coli strains tested with the DDM. To assess historical changes in antimicrobial drug resistance, subgroup analysis from 2000 to 2018 showed a significant increase in ciprofloxacin resistance.Conclusion: Monitoring and evaluating antibiotic-sensitivity patterns and preparation of reliable antibiotic strategies may lead to better outcomes for inhibition and control of E. coli infections in different regions of the world.Keywords: antibiotic, drug resistance, Escherichia coli