Peptide nucleic acid-mediated re-sensitization of colistin resistance Escherichia coli KP81 harboring mcr-1 plasmid

Escherichia coli is a gram-negative bacterium and it causes a variety of diseases in humans. It causes a wide range of clinical infections in humans; urinary tract infections is the most prevalent infection caused by uropathogenic Escherichia coli. In recent years, the observation of antibiotic-resistant genes such as resistance to colistin, makes the Escherichia coli resistant to antibiotics like colistin (polymyxin E), because of that the use of new therapies like peptide nucleic acid (PNA) has attracted the consideration of scientists. The aim of this study is the assessment of the inhibitory role of PNA against mcr-1 gene and reduction of mcr-1 gene expression and MIC in colistin resistant E. coli by PNA. NCBI database was used to design PNA. Our study was carried out on E. coli KP81 bacteria containing the mcr-1 gene. Microbroth dilution (MIC) method was used to survey phenotypic sensitivity and determine the sensitivity of the bacteria to the colistin antibiotic. E. coli KP81 isolates were further investigated by polymerase chain reaction to assess the presence of mcr-1 genes and target genes were quantified by real-time PCR assay using specific primers. The MIC result after treatment with specific PNA showed that the resistance to colistin reduced about three fold and the resistance level dropped from 32 μg/ml to 4 μg/ml. The expression analysis of mcr-1 gene in E. coli KP81 isolate indicates the PNA, 95% reduced the expression of the mcr-1 gene. Our observations showed that by inhibiting the expression of mcr-1, sensitivity to colistin can be defeated. Using higher concentrations of PNA and an in vivo study can reveal more clinical application of this method. •Designed PNA, reduced 95% of the expression of mcr-1 gene.•Designed PNA, dropped sensitivity of E. coli KP81 to colistin of from 32 μg/ml to 4 μg/ml.•By inhibiting the expression of mcr-1, sensitivity to colistin can be defeated.•Higher concentrations of PNA are needed for plasmid related genes.