First Detection of Colistin Resistance Encoding Gene mcr-1 in Clinical Enterobacteriaceae isolates in Morocco

 Since first reported in 2015, the mobile colistin resistance (mcr-1) gene has been found in increasing numbers worldwide. However, only a few studies have been carried out in Morocco. Herein, we aimed to investigate the prevalence of colistin resistance and mcr-like genes among Enterobacteriaceae clinical isolates from the North-West of Morocco.

 The prevalence of colistin resistance was investigated among 338 Enterobacteriaceae clinical isolates. These isolates were collected from Tangier and Tetouan cities between December 2020 and May 2021. The isolates included Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), Enterobacter spp, Citrobacter freundii (C. freundii), and Proteus mirabilis (P. mirabilis). Antibacterial susceptibility tests were performed using disc diffusion assay and minimal inhibitory concentrations (MIC). All isolates that were found resistant to colistin were subjected to PCR and sequencing techniques to screen them for the presence of mcr-like genes (mcr-1 to mcr-5).

 22.78% of isolates were multidrug-resistant (MDR), among which 57.14% of P. mirabilis isolates, 30% of Enterobacter spp isolates, 22.22% of K. pneumoniae isolates, and 22.05% of E. coli isolates. Colistin resistance was found in 51 of 338 isolates, including 33 E. coli, 11 K. pneumoniae, and 7 P. mirabilis. The mcr-1 gene was detected in 3 E. coli isolates. Mcr-2 to mcr-5 genes were absent in this study. Sequencing of PCR amplicons revealed 99–100% similarity to mcr-1 gene.

 This is the first study conducted in Morocco to investigate the prevalence of colistin resistance among clinical isolates, and it has revealed the first three mcr-1 genes circulating in Morocco. This could lead to the dissemination of these genes throughout Morocco.