VRE

VRE
Name	Vancomycin-resistant enterococci
Domain	Bacteria
Phylum	Firmicutes
Classis	Bacilli
Ordo	Lactobacillales
Familia	Enterococcaceae
Genus	Enterococcus
Species	Enterococcus faecalis, Enterococcus faecium

VRE Vancomycin-resistant enterococci are strains of Enterococcus—principally Enterococcus faecalis and Enterococcus faecium—that have acquired resistance to the glycopeptide antibiotic vancomycin. First described during the late 20th century amid rising antimicrobial resistance concerns involving institutions such as the Centers for Disease Control and Prevention and hospitals in Europe and North America, these organisms are major causes of healthcare-associated infections linked to outbreaks in facilities like Johns Hopkins Hospital and Mayo Clinic. VRE intersect with clinical, microbiological, and public health domains including influences from policies such as the Infectious Diseases Society of America guidelines and surveillance systems like the National Healthcare Safety Network.

Definition and microbiology

VRE are members of the genus Enterococcus within the family Enterococcaceae, characterized as Gram-positive, facultatively anaerobic, catalase-negative cocci that form short chains or pairs. The principal species associated with vancomycin resistance are Enterococcus faecalis and Enterococcus faecium, with resistance commonly mediated by van gene clusters (e.g., vanA, vanB) that alter the target of vancomycin—the D-Ala-D-Ala terminus—into D-Ala-D-Lac or D-Ala-D-Ser. Horizontal gene transfer via transposons (notably Tn1546) and conjugative plasmids has been documented in comparative genomic studies from institutions like Harvard Medical School and University of Oxford, facilitating spread across strains and between species. Laboratory identification leverages phenotypic methods used in Clinical and Laboratory Standards Institute protocols and genotypic assays developed by groups at Centers for Disease Control and Prevention and Public Health England for detection of van gene variants.

Epidemiology and risk factors

Epidemiology of VRE reflects concentration in acute-care hospitals, long-term care facilities, and oncology centers such as Memorial Sloan Kettering Cancer Center, with increasing detection in community settings linked to global dissemination patterns reported by the World Health Organization. Risk factors include prior exposure to broad-spectrum agents championed in stewardship debates—such as cephalosporins and carbapenems—as well as recent use of vancomycin; prolonged hospitalization; presence of invasive devices like central venous catheters used in Mayo Clinic protocols; immunosuppression seen in patients treated at Fred Hutchinson Cancer Research Center; and complex surgical procedures performed at centers like Cleveland Clinic. International travel, transfers between facilities (e.g., from academic medical centers to long-term care), and agricultural practices highlighted by studies from University of California, Davis have also been implicated in regional dissemination.

Clinical presentation and diagnosis

VRE commonly colonize the gastrointestinal tract and perineum before causing infection. Clinical syndromes include bloodstream infection associated with central lines (described in case series from Johns Hopkins Hospital), urinary tract infection in patients with indwelling catheters treated at Mayo Clinic, surgical site infections after procedures at Massachusetts General Hospital, and intra-abdominal infections managed in Royal Free Hospital case series. Less commonly, endocarditis has been reported in cohorts from Cleveland Clinic and University College London Hospitals. Diagnosis relies on culture of sterile sites and selective media evaluated by laboratories participating in Clinical and Laboratory Standards Institute schemes; automated systems such as those developed by BD Diagnostics and bioMérieux assist identification, while molecular assays from academic groups at Johns Hopkins and Karolinska Institutet detect van gene motifs. Susceptibility testing follows breakpoint guidance from bodies like European Committee on Antimicrobial Susceptibility Testing.

Treatment and management

Therapeutic options for VRE infections depend on species, site of infection, and resistance genotype. Linezolid, daptomycin, tigecycline, and newer agents such as ceftazidime‑avibactam combinations evaluated in multicenter trials involving institutions like Stanford University and University of Pennsylvania are commonly used; antimicrobial stewardship programs modeled on Infectious Diseases Society of America recommendations guide agent selection and duration. For bacteremia, removal of infected devices as recommended by specialist teams at Mayo Clinic is critical. Pharmacokinetic and pharmacodynamic monitoring informed by research from University of California, San Francisco and dose-optimization protocols from National Institutes of Health play roles in management. Experimental strategies—including bacteriophage therapy investigated at Erasmus Medical Center and fecal microbiota transplantation studied at University of Minnesota—are under evaluation in clinical trials sponsored by entities like the National Institute of Allergy and Infectious Diseases.

Infection control and prevention

Infection control measures derive from guidelines issued by organizations such as the Centers for Disease Control and Prevention, Public Health England, and World Health Organization. Strategies include active surveillance cultures used in outbreak responses at Johns Hopkins Hospital, contact precautions implemented in surgical wards at Massachusetts General Hospital, hand hygiene campaigns modeled after initiatives at Saskatchewan Health Authority, environmental cleaning protocols adopted by Guy's and St Thomas' NHS Foundation Trust, and antimicrobial stewardship programs developed at Infectious Diseases Society of America. Cohorting of colonized patients and staff, terminal cleaning after discharge, and decolonization trials guided by research from University of Oxford and Imperial College London have been employed during institutional outbreaks.

Public health impact and surveillance

VRE contribute to the burden of healthcare-associated infections tracked by surveillance systems such as the National Healthcare Safety Network, European Antimicrobial Resistance Surveillance Network, and national programs run by ministries of health in Canada, Australia, and Japan. Economic analyses from Harvard School of Public Health and outcome studies from Johns Hopkins Bloomberg School of Public Health quantify increased length of stay, attributable mortality, and healthcare costs associated with VRE. International collaborations—including efforts coordinated by the World Health Organization and research consortia at University College London—aim to monitor trends, inform policy, and prioritize research into novel therapeutics and prevention strategies.

Category:Antibiotic-resistant bacteria