LAUSR

Colistin is one of our last line of therapy against multi-drug resistant Gram-nevative pathogens especially carbapenemases producers, which makes from resistance to this compound a major global public health crisis. Until recently, colistin resistance in Gram-negative bacteria (GNB) was known to be emerged only by chromosomal mutations. However, a plasmid-mediated mobile colistin resistance (mcr) mechanism has been described in late 2015. This mechanism is encoded by different mcr genes that encode for phosphoethanolamine transferase enzymes. These latter ensure the addition of phosphoethanolamine moiety to lipid A of the bacterial outer membrane leading to colistin resistance. MCR-producing GNB have been largely disseminated worldwide. However, their environmental dissemination has been underestimated. Indeed, water environments act as a connecting medium between different environments, allowing them to play a crucial role in the spread of antibiotic resistance between the natural environment and humans and other animals. For a better understanding of the role of such environments as reservoirs and/or dissemination routes of mcr genes, this review discussed primarily the various water habitats contributing to the spread of antibiotic resistance. Thereafter, we provided an overview on the existing knowledge regarding the global epidemiology of mcr genes in water environments. This review confirms the global distribution of mcr genes in several water environments, including wastewater from different origins, surface water and tap water, making from these environments reservoirs and dissemination routes of concern for this resistance mechanism.