Vancomycin-Resistant Enterococcus (VRE): Risk Factors, Causes, Diagnosis, Treatment, Prevention

 Vancomycin-Resistant Enterococcus (VRE)

Vancomycin-Resistant Enterococcus (VRE) Enterococci are gram-positive, facultative anaerobic organisms usually oval in shape and can be seen as single cells, pairs, or chains. Vancomycin-resistant Enterococcus (VRE) are enterococci that have become resistant to vancomycin and several antibiotics normally used to treat enterococcal infections.

RISK FACTORS OF VANCOMYCIN-RESISTANT ENTEROCOCCUS

• Prior antimicrobial therapy, especially vancomycin

• Prolonged hospitalization

• Chronic medical conditions, renal failure

• Invasive devices

• ICU stay

• Colonization: VRE colonize the gastrointestinal tract; can be found on skin or perirectal swab culture or stool culture

PHYSICAL FINDINGS & CLINICAL PRESENTATION

Patients may be asymptomatic and have gastrointestinal colonization; it can be associated with diarrhea. In hospitalized patients, infection is associated with colonization and can cause wound infections, bacteremia, abscesses (intraabdominal), and, rarely, pneumonia, urinary tract infections, and endocarditis.

CAUSES OF VANCOMYCIN-RESISTANT ENTEROCOCCUS

• The Clinical and Laboratory Standards Institute uses the following MIC definitions for vancomycin susceptibility and resistance in enterococci:

1. Vancomycin susceptible: ≤4 mcg/ml

2. Vancomycin-resistant: ≥32 mcg/ml

3. Vancomycin intermediate: 8 to 16 mcg/ml 

(vancomycin not recommended)

• Enterococci are primarily found in the human digestive tract and female genital tract, where they make up a significant portion of the normal bacterial population in healthy people. Enterococci can cause urinary tract, wound, bloodstream, heart valve, and brain infections. In the great majority of cases, VRE infections occur in hospitalized patients who have compromised immune systems. Most cases of VRE are caused by the E. faecium strains that have acquired resistance when they came in contact with other bacteria and shared genetic information.

• VRE is most commonly transmitted from one patient to another by health care workers whose hands have become contaminated inadvertently with faeces or fluids of a person carrying the organism. VRE are not airborne but can survive on surfaces for several weeks.

DIAGNOSIS OF VANCOMYCIN-RESISTANT ENTEROCOCCUS

DIFFERENTIAL DIAGNOSIS

• Other bacterial pathogens in blood, wounds, or urine

• Once colonized, increased incidence to become infected

LABORATORY TESTS

• VRE rectal culture

• VRE stool culture

• Blood, urine, and wound cultures

TREATMENT OF VANCOMYCIN-RESISTANT ENTEROCOCCUS

• For rectal or stool colonization, therapy is not recommended

• Therapy is complicated by the fact that strains exhibit inherent resistance to many commonly used antibiotics.

• More than 80% of vancomycin-resistant E. faecium strains are also resistant to ampicillin.

• In symptomatic patients, if VRE strains are known to be susceptible, potential therapeutic agents include

• Linezolid: 600 mg IV or PO q12h

• Daptomycin: 4 mg/kg/day IV for nonbacteremia infections and 6 mg/kg/day IV for bacteremias

• Tigecycline: 100 mg IV load dose, then 50 mg IV q 12 hr. Although not specifically FDA approved for VRE strains, it offers an option for patients intolerant to other agents.

• Quinupristin-dalfopristin (Synercid) only effective for E. faecium strains with no activity for E. faecalis strains: 7.5 mg/kg q8 to 12h. Can cause severe myalgias and arthralgias and venous irritation that often requires use of a central line, which has limited the use of this antibiotic.

• Salvage regimens for severe VRE infections include:

  ■ daptomycin plus gentamicin and/or 

ampicillin or ceftaroline

  ■ daptomycin plus tigecycline

• The Healthcare Infection Control Practices Advisory Committee recommends that three negative stool/rectal cultures be obtained at weekly intervals to remove a patient from contact precautions.

PREVENTION OF VANCOMYCIN-RESISTANT ENTEROCOCCUS

• Hand hygiene: most important and practical method of preventing spread in hospital environment. Soap and water (used as a 30-sec wash) and alcohol-based hand rubs are effective, as is chlorhexidine.

• Cohorting and isolation techniques: use of private rooms and use of gowns and gloves has been shown to decrease the risk of spread of multidrug-resistant bacteria.

• Cleaning contaminated objects or surfaces with standard hospital disinfectants, antibiotic management (prudent vancomycin use), and surveillance also help prevent spread.