Plasmid-MediatedvanBGlycopeptide Resistance in Enterococci

Abstract

Enterococcus faecium, which was highly resistant to vancomycin (MIC 256 mg/liter), but susceptible to teicoplanin (MIC 2 mg/liter), caused two distinct episodes of infection on a renal unit in the United Kingdom. Pulsed field gel electrophoresis (PFGE) indicated that a single strain caused the first episode, while the second episode, which occurred 1 year later, involved multiple strains, all of which were distinct from the original strain. Vancomycin resistance in all but one of these strains was mediated by transferable plasmids that carried the vanB glycopeptide resistance gene. Transfer either of resistance plasmids or the vanB resistance determinant itself to different strains occurred during the second episode. Plasmid-mediated vanB resistance has not been widely documented. A retrospective study of a reference collection revealed two other vanB-encoding plasmids from an E. faecalis and an E. faecium referred from two further UK centers. Although restriction analysis indicated no similarity between the plasmids from the three different centers, all contained a 2.1-kb EcoRV fragment that hybridized with a probe for the vanB gene. This suggests that there has been dissemination of a conserved glycopeptide resistance determinant, of which vanB is a part.

Glycopeptide-resistant enterococci: a decade of experience

“…Given the distribution of affected hospitals throughout the UK [12], these data suggest that most GRE have emerged independently at a number of different centres, rather than simply spreading between centres. Furthermore, the wide distribution of the VanA and VanB resistance phenotypes, both of which have been associated with outbreaks [30,45,761, argues that these two genetically distinct, complex resistance mechanisms have arisen in multiple strains in this country. Even though the resistance genes may be transferable, the available data based on the analysis of nosocomial GRE do not provide an easy explanation for these observations and suggest that the true epidemiology of GRE is complex and includes stages outside of the hospital environment.…”

Enterococcus gallinarum carrying the vanA gene cluster: first report in Brazil

“…This isolate was sent to a reference laboratory (Laboratório Especial de Bacteriologia e Epidemiologia Molecular, Faculdade de Ciências Farmacêuticas de Ribeirão Preto) for further study and proved to be an E. gallinarum (termed ET193) by the polymerase chain reaction (PCR) using specific primers for the species (11). Due to the phenotype of unusually high level of vancomycin resistance, the isolate was tested for the presence of specific resistance genes (vanA and vanB) by PCR, which indicated the presence of the vanA gene (14,15).…”

Characterization of Tn 1546 in Vancomycin-Resistant Enterococcus faecium Isolated from Canine Urinary Tract Infections: Evidence of Gene Exchange between Human and Animal Enterococci

“…In Europe, the vanA transposable element has been identified in enterococci isolated in the community and from sewage, animal feces, and raw meat, suggesting that each of these may act as a reservoir of both resistant enterococci and the vanA gene (1,4,9,37,38,40,42). The occurrence of vanA outside of the hospital environment has been attributed to the use in Europe of the glycopeptide avoparcin as a growth promoter in pigs and poultry (23).…”

“…The concurrent appearance of vanA in both Europe and the United States, despite the lack of avoparcin use in the United States, suggests that the epidemiology and global dissemination of vanA are complex (38,40). Tn1546 is often associated with plasmids, and several reports have emphasized the fact that there are polymorphisms between Tn1546 elements due to insertions, deletions, and point mutations (10,13,14,(36)(37)(38)(39)42).…”

“…Recently, 24 Tn1546 types were described in Europe and the United States. Some types were specific to human or animal vancomycin-resistant enterococcus isolates, while others were common to both human and animal vancomycin-resistant enterococcus isolates (36)(37)(38). Each study indicated a possible role of animals as a source of vancomycinresistant enterococci, but none of these studies was conclusive.…”