Abstract

Wastewater from various sources, households, hospitals, veterinary and animal husbandry as well as pharmaceutical factories is a reservoir of an array of antimicrobial compounds and multi-resistant bacteria (MDR). The global increase of MDR and Extra-Drug Resistant (XDR) Gram-negative bacteria especially Enterobacterales in human medicine has led to the reintroduction of colistin as last-resort antibiotic. Colistin is the only salvage therapy especially in case of carbapenemase producing strains among multi-resistant Gram-negative bacterial species. Although there is no available data in the recent past on the content of colistin residues in wastewater, there exists numerous scientific reports on colistin resistance among Gram-negative bacteria, more so among the members of the order Enterobacterales. At first, mechanisms attributed to colistin resistance were associated with mutations in genes domiciled on the chromosome. However, the presence of mobilizable colistin resistance genes on transferrable plasmids among Gram-negative bacteria continue to be documented in wastewater in different regions after the initial discovery of mcr-1 gene in China in 2016.