Comparative epidemiology and resistance mechanisms of carbapenem-, tigecycline-, and polymyxin-resistant Enterobacteriaceae in pediatric diarrhea: A cross-sectional study in 2017 and 2023.

OBJECTIVES

To compare the epidemiology and resistance mechanisms of carbapenem-, tigecycline-, and polymyxin-resistant Enterobacteriaceae isolated from pediatric diarrhoea cases in 2017 and 2023.

METHODS

Fecal samples from children with diarrhoea were collected in Zhejiang, China, in 2017 and 2023. Bacterial isolation, antimicrobial susceptibility testing, and whole-genome sequencing were performed to identify resistance determinants and plasmid types.

RESULTS

The prevalence of mcr-1-positive strains declined significantly from 2.36% (25/1059) in 2017 to 0.82% (3/367) in 2023, while tet(X4)-positive strains rose from 0% to 1.91% (7/367). Carbapenemase-producers remained rare (0.28% in 2017; 1.63% in 2023), with blaNDM as the dominant carbapenemase gene. Whole genome sequencing revealed diverse antimicrobial resistance genes (ARGs) and evolving plasmid types. Notably, by 2023, all mcr-1 were carried on IncI2 plasmids. Conjugation experiments confirmed plasmids carrying mcr-1, blaNDM-5, and tet(X4) are transferable to a recipient strain.

CONCLUSIONS

The rising prevalence of multidrug-resistant Enterobacteriaceae in pediatric diarrhoea highlights the urgent need for continuous surveillance and effective infection control measures.