Emergence of Escherichia coli harbouring mcr-1 and mcr-3 genes in North West Algerian farmlands

Objectives: Colistin resistance has emerged worldwide, threatening the ef ficacy of colistin treatment of Gram-negative bacterial infections. Farms have been recognised as an important reservoir of genes conferring resistance to colistin. This study aimed to isolate and characterise colistin-resistant bacteria in farmlands located in the region of Oran, northwest Algeria. Methods: Forty environmental samples were collected between May 2016 and March 2018 at eight agricultural sites in the Oran region. Results: From the 40 samples, 103 colistin-resistant isolates were isolated from agricultural soil (n = 52), irrigation water (n = 31) and manure (n = 20). Eight isolates were identi fied as Escherichia coli , including six and two isolates carrying the mcr-1 and mcr-3 gene, respectively. All eight E. coli isolates were non-susceptible to amoxicillin, amoxicillin/clavulanic acid, ticarcillin, nalidixic acid, cipro floxacin, gentami-cin, trimethoprim/sulfamethoxazole and rifamycin; two were also non-susceptible to cefotaxime, cefepime and aztreonam and carried the bla TEM-12 gene in addition to mcr-1 . The six mcr-1-carrying E. coli isolates (MIC >= 2 m g/mL) belonged to three sequences types, including ST10 (n = 3), ST405 (n = 2) and ST345 (n = 1), whereas the two mcr-3-carrying isolates were assigned to ST155. The conjugation assay was positive only for two mcr-1-positive isolates. Conclusion: These results show that farms are an important reservoir of colistin-resistant E. coli as well as other antimicrobial resistance genes such as ESBL genes. Transfer of manure from animals to soil and irrigation water might be disseminating a mix of multiple resistances, posing a worrying threat to human health. (C) 2019 International Society for Antimicrobial Chemotherapy. Published by Elsevier Ltd.