Prevalence and Traits of Mobile Colistin Resistance Gene Harbouring Isolates from Different Ecosystems in Africa

Abstract

The mobile colistin resistance (mcr) gene threatens the efficacy of colistin (COL), a last-line antibiotic used in treating deadly infections. For more than six decades, COL is used in livestock around the globe, including Africa. The use of critically important antimicrobial agents, like COL, is largely unregulated in Africa, and many other factors militate against effective antimicrobial stewardship in the continent. Currently, ten mcr genes (mcr-1 to mcr-10) have been described. In Africa, mcr-1, mcr-2, mcr-3, mcr-5, mcr-8, and mcr-9 have been detected in isolates from humans, animals, foods of animal origin, and the environment. These genes are harboured by Escherichia coli, Klebsiella, Salmonella, Citrobacter, Enterobacter, Pseudomonas, Aeromonas, Alcaligenes, and Acinetobacter baumannii isolates. Different conjugative and nonconjugative plasmids form the backbone for mcr in these isolates; however, mcr-1 and mcr-3 have also been integrated into the chromosome of some African strains. Insertion sequences (ISs) (especially ISApl1), either located upstream or downstream of mcr, class 1 integrons, and transposons, are drivers of mcr in Africa. Genes coding multi/extensive drug resistance and virulence are colocated with mcr on plasmids in African strains. Transmission of mcr to/among African strains is nonclonal. Contact with mcr-habouring reservoirs, the consumption of contaminated foods of animal/plant origin or fluid, animal-/plant-based food trade and travel serve as exportation, importation, and transmission routes of mcr gene-containing bacteria in Africa. Herein, the current status of plasmid-mediated COL resistance in humans, food-producing animals, foods of animal origin, and environment in Africa is discussed.

Metagenomic analysis of the abundance and composition of antibiotic resistance genes in hospital wastewater in Benin, Burkina Faso, and Finland

“…For example, while banned in many other countries, the use of colistin as a feed additive is allowed in many LICs (63), such as those in Africa (7). In contrast to previous reports on the prevalence of mobile colistin resistance globally (30) and in Africa (31,64), mcr-5 was the most commonly detected gene in the HWWs from our study. Instead, our observations are in line with the results obtained by using both metagenomics and qPCR (65).…”

“…This is the first study investigating hospital wastewaters in the two West African countries using a metagenomic approach. Due to the lack of systematic AMR surveillance in these countries, available data on bacterial resistance are patchy and heterogenous 1,4,31,34,37 . Thus, the magnitude of the resistance problem and the specific reservoirs of ARGs in many African countries are yet to be unraveled.…”

“…Colistin is a last-resort antibiotic used for treating infections caused by multidrug and extensively resistant bacteria 26 . The rapid emergence of mobile colistin resistance mediated by mcr genes threatens the efficacy of colistin in clinical use 27,28 .…”

Genomic Insights into a Colistin-Resistant Uropathogenic Escherichia coli Strain of O23:H4-ST641 Lineage Harboring mcr-1.1 on a Conjugative IncHI2 Plasmid from Egypt

“…Additional genes were detected alongside mcr-1 and were associated with resistance to aminoglycosides (aadA2), streptothricin (sat1) and amphenicols (cmlA1) (Figure 3A). The co-existence of other antibiotic resistance genes on mcr-1-carrying plasmids presents the hazard of screening colistin-resistant strains under the imposed selective pressure exerted by antibiotics other than colistin [42].…”

Colistin resistance in Escherichia coli confers protection of the cytoplasmic but not outer membrane from the polymyxin antibiotic

“…Since we only examined one isolate with mcr- 5 it is not clear whether this is representative of other E. coli strains carrying this mcr gene, which are more commonly associated with livestock than humans [22, 35–37]. However, mcr-5 is phylogenetically distinct from all other mcr variants described to date, which may explain the lower level of protection against colistin-mediated CM disruption we observed [38, 39].…”