Molecular Analysis of Polymyxin Resistance among Carbapenemase-Producing in Colombia.

Polymyxin resistance in has been attributed to mutations in , , , and and to the presence of plasmid-mediated genes. Herein, we describe the molecular characteristics of 24 polymyxin- and carbapenem-resistant isolates recovered from six Colombian cities between 2009 and 2019. Minimum inhibitory concentrations (MICs) to polymyxin were confirmed by broth microdilution, and whole-genome sequencing was performed to determine sequence type, resistome, and mutations in the genes related to polymyxin resistance, as well the presence of . The results showed high-level resistance to polymyxin (MICs ≥ 4 μg/mL). was present in the majority of isolates (17/24; 71%), followed by (6/24; 25%) and (1/24; 4%). Most isolates belonged to the CG258 (17/24; 71%) and presented amino acid substitutions in PmrB (22/24; 92%) and CrrB (15/24; 63%); mutations in occurred in only five isolates (21%). Additional mutations in , , and nor any of the mcr resistance genes were identified. In conclusion, we found clonal dissemination of polymyxin and carbapenem-resistant isolates in Colombia, mainly associated with CG258 and . Surveillance of this multidrug-resistant clone is warranted due to the limited therapeutic options for the treatment of carbapenem-resistant infections.