Synergistic Effect of Colistin and Rifampin Against Multidrug Resistant Acinetobacter baumannii: A Systematic Review and Meta-Analysis

Maryam Mohammadi1, Hatef Khayat1, Koroush Sayehmiri2, Setareh Soroush3, Fatemeh Sayehmiri4, Somayeh Delfani3, Lidija Bogdanovic5, Morovat Taherikalani3, *
1 Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran
2 Department of Biostatistics, School of Medicine, Ilam University of Medical Sciences, Ilam, Iran
3 Razi Herbal Medicines Research Center & Department of Microbiology, School of Medicine, Lorestan University of Medical Sciences, Khorramabad, Iran
4 Proteomics Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
5 Department of Public Health, University of Naples Federico II, Naples, Italy

Article Metrics

CrossRef Citations:
Total Statistics:

Full-Text HTML Views: 5847
Abstract HTML Views: 2741
PDF Downloads: 1307
ePub Downloads: 686
Total Views/Downloads: 10581
Unique Statistics:

Full-Text HTML Views: 2552
Abstract HTML Views: 1475
PDF Downloads: 913
ePub Downloads: 476
Total Views/Downloads: 5416

Creative Commons License
© 2017 Mohammadi et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Razi Herbal Medicines Research Center &Department of Microbiology, School of Medicine, Lorestan University of Medical Sciences, Khorramabad, Iran; Tel: +98 66 33227593; Fax: +98 66 33227593; E-mails:,


The existence of infections caused by multidrug resistant (MDR) Acinetobacter baumannii is a growing problem because of the difficulty to treat them. We examined the published literature and focused our analysis on the investigation of the synergism of colistin and rifampin against MDR A. baumannii isolates via systematic review and meta-analysis. A systematic literature search was performed using the following 4 databases (PubMed, Scopus, EMBASE and ISI Web of Sciences). The related articles were evaluated during the period from December 2014 to January 2015. Information based on resistance and sensitivity to antibiotics, the minimum inhibitory concentration and the effects of two antibiotics on each other including synergism, antagonism, relative synergism and additive antagonism were extracted. A meta-analysis of 17 studies including 448 samples was brought into process and 2% (95% CI 0-4%) and 72% (95% CI 56-89%) resistance to colistin and rifampin were observed, respectively. 42% of all isolates showed MIC = 4 µg/ml (95% CI 14-69%) to rifampin and 30% MIC= 2 µg/ml to colistin (95% CI 3.8-78%). MIC50 and MIC90 for both rifampin and colistin were 2 µg/ml and 4 µg/ml, respectively. 63% of the strains demonstrated synergy (95% CI 37-90%), 7% were highlighted as relative synergism (95% CI 0.0- 13%), 3% showed an additive effect (95% CI -0.0-7%) and 14% were indifferent (95% CI 6-23%). The antagonistic effect was not observed in this combination. Synergy rates of time-kill assay in rifampin and colistin combinations were generally higher than those of check bored microdilution and E-test method. The results demonstrated that the combination therapy could be more useful when compared to monotherapy and that this strategy might reduce the resistance rate to rifampin in MDR A. baumannii isolates.

Keywords: Synergism, Colistin, Rifampin, A. baumannii.