Significance and Impact of the Study: Increasing usage of antimicrobial compounds in human and veterinary medicine has contributed to the global emergence and transmission of antimicrobial-resistant bacteria, representing a major concern for human and animal health. According to many international and governmental organizations, the impact of antimicrobial resistance will be particularly significant in low-income regions across Africa, Asia, and Latin America. Accordingly, the development and implementation of multidisciplinary (i.e. One Health) evidence-based control programs and strategies are critical. Colistin is a ‘last-resort’ antimicrobial treatment for multidrug-resistant Gram-negative infections including pneumonia from Enterobacterales; however, high rates of colistin resistance have been reported globally, including Africa. A more profound understanding of the molecular mechanisms underlying colistin resistance is required for the development of effective surveillance programs and innovative therapies against multidrug-resistant bacteria.

Abstract

Colistin (also known as polymyxin E), a polymyxin antibiotic discovered in the late 1940s, has recently reemerged as a last-line treatment option for multidrug-resistant infections. However, in recent years, colistin-resistant pathogenic bacteria have been increasingly reported worldwide. Accordingly, the presented review was undertaken to identify, integrate and synthesize current information regarding the detection and transmission of colistin-resistant bacteria across the African continent, in addition to elucidating their molecular mechanisms of resistance. PubMed, Google Scholar and Science Direct were employed for study identification, screening and extraction. Overall, based on the developed literature review protocol and associated inclusion/exclusion criteria, 80 studies published between 2000 and 2021 were included comprising varying bacterial species and hosts. Numerous mechanisms of colistin resistance were reported, including chromosomal mutation(s) and transferable plasmid-mediated colistin resistance (encoded by mcr genes). Perhaps unexpectedly, mcr-variants have exhibited rapid emergence and spread across most African regions. The genetic variant mcr-1 is predominant in humans, animals and the natural environment, and is primarily carried by IncHI2- type plasmid. The highest number of studies reporting the dissemination of colistin-resistant Gram-negative bacteria were conducted in the North African region.