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.