Enterococci are bacteria commonly found in human intestines, the female genital tract, and in the environment. These bacteria typically reside harmlessly within the body as part of its natural flora. Vancomycin is a powerful antibiotic used to treat serious bacterial infections, especially those caused by gram-positive bacteria when other treatments are ineffective.
Vancomycin-resistant Enterococcus, or VRE, refers to strains of enterococci that have developed resistance to vancomycin. This means the antibiotic can no longer effectively treat infections caused by these bacteria. The emergence of VRE poses a challenge by limiting available treatment options. VRE is primarily a concern within healthcare environments, including hospitals and long-term care facilities, where most VRE infections are acquired.
Transmission and Primary Risk Factors
VRE primarily spreads through direct contact with individuals colonized or infected with the bacteria, often via the hands of healthcare personnel with inadequate hand hygiene. It can also spread through indirect contact with contaminated surfaces or medical equipment in healthcare settings, such as bed rails, door handles, or shared patient care devices. VRE is not typically airborne but spreads through physical contact.
Several factors increase an individual’s susceptibility to acquiring VRE, particularly in hospital settings. Prolonged hospitalization is a risk factor, especially for patients in intensive care units or those with extended stays in long-term care facilities. Individuals with weakened immune systems, such as organ transplant recipients or those undergoing chemotherapy, are also at higher risk. Recent major surgeries, particularly complex abdominal or chest procedures, can predispose patients to VRE acquisition.
The presence of indwelling medical devices, including urinary catheters, central intravenous catheters, and feeding tubes, also increases risk by providing pathways for bacterial entry. Prior or prolonged treatment with vancomycin or other broad-spectrum antibiotics can disrupt normal gut flora, promoting the growth of resistant strains like VRE. Antibiotic exposure, especially to vancomycin and anti-anaerobic antibiotics, is an independent risk factor for VRE acquisition.
Distinguishing Between Colonization and Infection
Understanding the difference between VRE colonization and infection is important. Colonization occurs when VRE bacteria are present in or on the body without causing illness or symptoms. These bacteria commonly reside harmlessly in the intestines or on the skin. Many individuals can carry VRE as part of their normal bacterial flora for extended periods without adverse effects.
In contrast, a VRE infection develops when the bacteria invade a part of the body where they are not typically found, leading to active disease and noticeable symptoms. This means the bacteria are actively multiplying and causing harm, requiring medical intervention. While many people may be colonized with VRE, a smaller subset will develop an infection. Colonization does not necessitate antibiotic treatment, whereas an active infection always requires targeted therapy.
Symptoms and Medical Diagnosis
The symptoms of a VRE infection are directly linked to the body site where the infection has occurred. If VRE infects the urinary tract, symptoms might include pain or burning during urination, frequent urges to urinate, and fever. A bloodstream infection (bacteremia) can manifest with generalized symptoms such as high fever, chills, and a rapid heart rate, indicating a systemic response.
When VRE infects a surgical wound or skin lesion, localized symptoms include increased redness, swelling, warmth around the wound site, and pus or other discharge. Individuals colonized with VRE will not exhibit these symptoms; symptoms only arise when an active infection is underway.
To diagnose a VRE infection, healthcare providers collect a sample from the suspected site, such as urine, blood, or a wound swab. The sample is sent to a microbiology laboratory for culture to identify the bacteria. If enterococci are identified, antibiotic susceptibility testing confirms vancomycin resistance and determines effective alternative antibiotics. Rapid molecular assays, such as PCR, can also detect specific VRE genes like vanA and vanB for quicker screening.
Treatment of Vancomycin-Resistant Infections
For a VRE infection, vancomycin is ineffective due to the bacteria’s resistance. Healthcare providers must use alternative antibiotics. The selection of the appropriate antibiotic depends on the results of laboratory susceptibility testing, which identifies which antibiotics the VRE strain remains sensitive to. The infection’s location also guides treatment decisions.
Alternative antibiotics for VRE infections include linezolid and daptomycin, often considered first-line options for systemic infections. Linezolid is effective against both Enterococcus faecium and Enterococcus faecalis, and can be administered orally or intravenously. Daptomycin, a lipopeptide antibiotic, is also used, particularly at higher doses (8-12 mg/kg once daily) for VRE bacteremia and other invasive infections.
Tigecycline, a glycylcycline antibiotic, is another alternative, though sometimes less preferred for bloodstream infections due to varying efficacy and potential side effects. Other antibiotics, such as quinupristin/dalfopristin, chloramphenicol, and doxycycline, may be considered based on specific susceptibility profiles. Quinupristin/dalfopristin typically lacks activity against Enterococcus faecalis. For uncomplicated urinary tract infections caused by VRE, oral options like fosfomycin or nitrofurantoin might be utilized.
If an infected indwelling medical device, such as a urinary catheter or central venous line, contributes to the infection, removing the device is often a part of the treatment strategy to help clear the infection. Combination therapy with multiple antibiotics may be considered for severe or refractory VRE infections, especially in cases like endocarditis, to enhance bacterial killing.
Institutional Prevention and Control Measures
Healthcare facilities implement strategies to prevent and control VRE spread, especially given its prevalence in these environments. Strict adherence to hand hygiene protocols by all healthcare workers is essential. This involves thorough handwashing or using alcohol-based hand sanitizers before and after patient contact, after removing gloves, and after contact with the patient’s immediate environment.
Contact precautions are routinely employed for patients known to be colonized or infected with VRE. This involves healthcare personnel donning disposable gloves and gowns upon entering the patient’s room to prevent bacterial transfer. These protective items are removed and discarded safely before leaving the patient’s immediate area to minimize cross-contamination.
When feasible, placing VRE-colonized or infected patients in private rooms helps minimize potential transmission. If private rooms are unavailable, patients with VRE may be cohorted, sharing a room with other VRE patients to contain the spread. Enhanced environmental cleaning and disinfection of patient rooms and shared medical equipment are also performed regularly. This includes frequently touched surfaces like bed rails, door handles, and commodes, cleaned with hospital-grade disinfectants to reduce environmental contamination.