Stability and genetic insights of the co-existence of , , and harboring conjugative IncI2 plasmid isolated from a clinical extensively-drug resistant ST744 in Shanghai.

BACKGROUND

Co-existence of colistin, β-lactam and carbapenem in multidrug-resistant isolates poses a serious threat to public health. In this study, we investigated and characterized the co-occurrence of , , and strain isolated from a clinical extensively-drug-resistant ST744 in Shanghai.

METHODS

Antimicrobial susceptibility test was carried out by agar dilution methods. Whole genome sequencing was conducted, and resistance genes, and sequence types of colistin in isolates were analyzed. Plasmid stability and amino acid mutations were assessed in isolates.

RESULTS

A colistin resistant ST744, named ECPX221, was identified out of 145 fecal samples collected. The strain carries a 60,168 IncI2 plasmid with the gene. The strain also has , , 14, , , , , , , and resistance genes. The plasmid pECPX221 was capable of conjugation with an efficiency of 2.6 × 10. Notably, 45% of the transconjugants were determined as -harboring in the colistin-free environment after 60 generation of passage. No mutations occurred in , , and gene in the -harboring transconjugants. Bioinformatic analysis indicated pECPX221 shared highly similar backbone with the previously reported -harboring pAH62-1, pMFDS1339.1, pSCZE4, and p2018-10-2CC. Furthermore, sequencing and phylogenetic analyses revealed a similarity between other MCR-1-homolog proteins, indicating that ECPX221 was colistin resistant.

CONCLUSION

The stable transferable -harboring plasmid found in the ST744 strain indicated the high risk to disseminate the extensively-drug-resistance phenotype among .