Prospective whole genome sequencing analysis reveals spread of a vanB carrying transposon among different vancomycin-resistant Enterococcus faecium clinical isolates in a non-endemic setting

Vancomycin-resistant enterococci (VRE), in particular E. faecium (VREfm), can cause (severe) nosocomial infections and have been responsible for (hospital) outbreaks. Spreading of VREfm can occur both clonally and by dissemination of mobile genetic elements. In this study, we report the prospective analysis of WGS data including both cgMLST and transposon analysis during a vanB VREfm outbreak. A total of 1358 real-time PCRs was performed. Two hundred fifty one specimens of 207 patients tested positive for vanB, resulting in a final 13 specimens obtained from 6 different patients from which vanB positive VREfm were isolated. These 6 patients harbored 7 isolates , belonging to 4 different cluster types: CT118 (n=2), CT2483 (n=3), CT2500 and CT2501. Transposon analysis revealed an identical Tn1549 in all 6 patients, that could be linked based on epidemiological data. A vanB VREfm outbreak in our hospital occured, including 6 patients with a total of 4 different isolates belonging to 4 different cluster types. Prospective in depth transposon analysis revealed dissemination of the transposon Tn1549, rather than clonal spread being the cause of the outbreak