Vancomycin-Resistant Enterococci (VRE) are strains of bacteria that have developed resistance to the powerful antibiotic vancomycin. Enterococci naturally inhabit the human gastrointestinal and female genital tracts, usually without causing harm. When these bacteria acquire resistance, VRE becomes a significant public health concern, particularly in healthcare environments. This acquired resistance means the first-line treatment for serious enterococcal infections is ineffective, making VRE a leading cause of hospital-associated infections.
Understanding Vancomycin-Resistant Enterococci
Enterococci are facultative anaerobic, gram-positive organisms widespread in the environment and the human gut. They are typically considered harmless commensals. Their natural hardiness allows them to tolerate harsh conditions, such as high salt concentrations and a wide range of temperatures, which contributes to their survival in hospital settings.
Vancomycin resistance develops when enterococci acquire new genetic material, often carried on mobile elements like plasmids, that alters their cell wall structure. Vancomycin normally works by binding to a specific structure in the cell wall called D-alanyl-D-alanine, preventing its formation and killing the cell. Resistance genes, such as vanA or vanB, allow the bacteria to substitute D-alanyl-D-lactate for the original structure, which vancomycin binds to poorly. This substitution reduces the antibiotic’s ability to interfere with cell wall synthesis, rendering the drug ineffective against VRE.
VRE colonization occurs when a person carries the bacteria in their body, typically in the intestines, without experiencing symptoms of illness. This state can persist for extended periods, and many people who are colonized never develop an infection.
VRE infection happens when the bacteria multiply and cause disease, resulting in symptoms like fever and pain at the site of infection. VRE can cause urinary tract infections, bloodstream infections (bacteremia), and infections of wounds or surgical sites. Infection development is much more likely in patients with weakened immune systems or those who are severely ill.
How VRE Spreads and Who is Most at Risk
VRE is primarily transmitted through direct or indirect contact, not through the air. The bacteria are often shed in the feces of colonized or infected individuals, contaminating environmental surfaces. Transmission occurs when healthcare personnel’s hands become contaminated after touching a patient or a surface, carrying VRE to another patient. VRE can survive on inanimate surfaces for up to four months, making environmental cleaning a crucial part of control.
Certain patient factors increase the likelihood of acquiring a VRE infection. A primary risk factor is prolonged exposure to antibiotics, particularly vancomycin or broad-spectrum agents, which disrupts the natural balance of gut bacteria and allows VRE to flourish. Patients who have spent extended periods in a hospital, especially in intensive care units or oncology wards, face a higher risk.
Individuals with compromised immune systems are highly susceptible. The presence of invasive medical devices creates pathways for the bacteria to enter the body and cause serious infections. Vulnerability to VRE acquisition is also increased by a history of major surgical procedures.
Risk Factors for VRE Acquisition
- Compromised immune systems (e.g., chemotherapy patients or organ transplant recipients).
- Underlying chronic diseases.
- Presence of invasive medical devices, including urinary and central venous catheters.
- Major surgical procedures, particularly abdominal or chest surgery.
Diagnosis and Treatment Options
Diagnosis of a VRE infection begins when a healthcare provider suspects the bacteria based on a patient’s symptoms and risk factors. A sample is collected from the suspected site of infection—such as blood, urine, or a wound swab—and sent to a laboratory. The lab grows the bacteria in a culture and performs tests to identify the organism as Enterococcus.
A susceptibility test determines if the isolated Enterococcus is resistant to vancomycin and other antibiotics. If resistance is confirmed, the organism is classified as VRE, and the lab results guide the clinical team in selecting an effective treatment. This process can take several days, requiring experienced clinical judgment in managing these infections.
Treatment is usually not required for patients who are only colonized with VRE and have no symptoms. Active VRE infection must be treated with alternative antibiotics, as vancomycin is ineffective. The choice of drug depends on the infection site and the VRE strain’s susceptibility profile, but options include newer agents like linezolid or daptomycin. For urinary tract infections associated with a catheter, removing the device can often help clear the infection.
Preventing the Spread of VRE
Preventing the spread of VRE in healthcare settings relies on infection control practices. Hand hygiene is paramount, requiring healthcare workers to wash their hands with soap and water or use an alcohol-based hand sanitizer before and after every patient encounter.
Patients known to be colonized or infected with VRE are often placed on contact precautions to prevent spread. These precautions involve healthcare providers wearing personal protective equipment, such as gloves and gowns, when entering the patient’s room. Environmental sanitation is also a focus, involving frequent and thorough cleaning of surfaces near the patient, such as bed rails and medical equipment.
Visitors should follow all posted instructions and practice hand hygiene before and after leaving the patient’s room. Hospitals also employ strategies like careful use of antibiotics, known as antimicrobial stewardship, to reduce the development of resistance and limit VRE problems.