Objectives: The emergence of NDM- and MCR-1-co-producing Escherichia coli has compromised the use of carbapenems and colistin, which are critically important in clinical therapy, and represents a severe threat to public health worldwide. Here, we demonstrate synergism of colistin combined with existing antibiotics as a potential strategy to overcome XDR E. coli co-harbouring NDM and MCR-1 genes.
Methods: To comprehensively evaluate their combined activity, antibiotic combinations were tested against 34 different E. coli strains carrying both NDM and MCR-1 genes. Antibiotic resistance profiles and molecular characteristics were investigated by susceptibility testing, PCR, MLST, S1-PFGE and WGS. Antibiotic synergistic efficacy was evaluated through in vitro chequerboard experiments and dose-response assays. A mouse model was used to confirm active combination therapies. Additionally, combinations were tested for their ability to prevent high-level colistin-resistant mutants (HLCRMs).
Results: Combinations of colistin with rifampicin, rifabutin and minocycline showed synergistic activity against 34 XDR NDM- and MCR-1-co-producing E. coli strains, restoring, in part, susceptibility to both colistin and the partnering antibiotics. The therapeutic effectiveness of colistin combined with rifampicin or minocycline was demonstrated in a mouse model. Furthermore, colistin plus rifampicin showed significant activity in preventing the occurrence of HLCRMs.
Conclusions: The synergism of colistin in combinations with rifampicin, rifabutin or minocycline offers viable therapeutic alternatives against XDR NDM- and MCR-positive E. coli.
- Anti-Bacterial Agents/administration & dosage
- Colistin/administration & dosage
- Disease Models, Animal
- Drug Resistance, Bacterial
- Drug Synergism
- Drug Therapy, Combination/methods
- Escherichia coli/drug effects
- Escherichia coli Infections/drug therapy
- Escherichia coli Proteins/metabolism
- Genotyping Techniques
- Mice, Inbred ICR
- Microbial Sensitivity Tests
- Treatment Outcome