Genetic characterization of vancomycin-resistant Enterococcus faecium isolates from neutropenic patients in Tunisia: spread of the pandemic CC17 clone associated with high genetic diversity in Tn1546-like structures.

This article focuses on the molecular characterization and epidemiology of vancomycin-resistant Enterococcus faecium (VREfm) isolates collected from hospitalized neutropenic patients in Tunisia between 2011 and 2016. The study found a significant increase in VREfm prevalence, rising from 2% to 27%, with all isolates harboring the vanA gene carried predominantly on truncated variants of the Tn1546 transposon, often associated with the rep17_pRUM plasmid. Molecular typing identified two major persistent clones, ST117 and ST80, both belonging to the high-risk clonal complex 17 (CC17), which exhibited multidrug resistance and carried multiple resistance genes including aac(6′)-Ie-aph(2′')-Ia, ermB, tetM, and aph(3′)-IIIa. Whole-genome sequencing of a representative ST117 isolate revealed the presence of five plasmids alongside a type I CRISPR-Cas system, suggesting complex mechanisms of resistance gene acquisition and persistence despite potential CRISPR-mediated barriers. The findings underscore the importance of continuous surveillance and infection control measures to limit the spread of these multidrug-resistant VREfm strains in healthcare settings.