Environmental mediation of colistin resistance in the African context. A systematic scoping review.

Objectives: The prevalence of antimicrobial resistance (AMR) among Gram-negative bacteria is a major global health concern. Resistance to last-resort antibiotics like colistin is particularly alarming. This study reviews how environmental factors have contributed to colistin resistance in the African context, where reports of colistin-resistant Gram-negative organisms are emerging.

Methods: A systematic review was conducted using multiple databases to identify articles on environmental mediation of colistin resistance in Africa. Search terms included "environment," "colistin," "mobile colistin resistance gene," and related keywords. Articles from 2015 to 2021 focusing on Africa were included. Data on country, genes detected, methods used, and bacterial species were extracted.

Results: Out of 847 articles identified, 26 were included in the final review. Studies were predominantly from Tunisia, Algeria, South Africa, Egypt, Nigeria, and Congo. The mobile colistin resistance (mcr-1) gene was the most common genetic variant detected. Escherichia coli (E. coli) was the predominant organism spreading mcr genes. Colistin-resistant genes were found in humans, animals, and environmental samples including manure, soil, water bodies, and wildlife.

Conclusions: This review confirms the rapid spread of plasmid-mediated colistin-resistant genes in humans, animals, and the environment across Africa. The movement of resistant genes between these reservoirs is alarming. There is a need for more research into colistin resistance mechanisms and implementation of continent-wide antibiotic stewardship programs to address this emerging threat in Africa. © 2024 The Author(s). Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy.