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Emergence of unusual vanA/vanB2 genotype in a highly mutated vanB2-Vancomycin Resistant Hospital Associated E. faecium background, in Vietnam

Santona, Antonella, Taviani, Elisa, Hoang, Hoa Minh, Fiamma, Maura, Deligios, Massimo, Ngo, Tram Viet Q, Van Le, An, Cappuccinelli, Pietro, Rubino, Salvatore, Paglietti, Bianca
International journal of antimicrobial agents 2018
Enterococcus faecium, cross infection, genes, genetic relationships, genotype, glycopeptides, hospitals, monitoring, multiple drug resistance, pathogens, phenotype, plasmids, sequence analysis, transposons, vancomycin, virulence, Vietnam
Enterococcus faecium has become a globally disseminated nosocomial pathogen principally as the consequence of acquisition and diffusion of virulence factors and multidrug resistance determinants, including glycopeptides, one of the last resort antimicrobials used to treat more serious infections that usually occur in high-risk patients.In this study we investigated and molecular characterized Hospital-Associated (HA) Enterococcus faecium isolates collected at Hue Central Hospital, Vietnam.Our results highlighted the spread among hospital wards of a surprisingly heterogeneous multi drugs resistant E. faecium population, composed by five different CC17-related STs, of which 46% VREf carrying the vanB gene. Whole genome Sequencing of selected E. faecium isolates showed that VREf from different STs carried the same chromosomal integrated Tn1549-like transposon, with a highly mutated vanB2-operon, showing an increased level of vancomycin resistance (VanB phenotype) and able, in one isolate, to confer resistance to teicoplanin (VanA incongruent phenotype).Two unusual vanA/vanB2-type strains were detected within the vanB2-type ST17 population, harbouring a Tn1546-vanA-like transposon in pJEG40-like plasmids. Wg-SNPs-based analysis evidenced the genetic relatedness of VSEf/VREf of same STs and suggested lateral exchange of the Tn1549-like element among isolates followed by clonal expansion. Particularly microevolution among ST17 isolates, including the vanA/vanB2-type strains, and inter-wards VREf transmission were highlighted.The use of teicoplanin is strongly discouraged in the study's hospital for the spreading of Tn1549–vanB2 associated to teicoplanin resistance. A rational use of glycopeptides and effective surveillance measures are always required to reduce nosocomial VSEF/VREf spread and to avoid the rise of unusual and misleading VREf genotypes.