Vancomycin-resistant Enterococcus (VRE)
Infection Control - prevention of spread

Raymond B. Otero, Ph.D.
Consultant

1. Introduction

Enterococci are a therapeutic challenge because of their intrinsic resistant to many antibiotics. Recent reports of enterococci with high-level resistance to multiple antibiotics have highlighted the rapidly decreasing therapeutic options for these organisms. As we enter an era of decreased antibiotic effectiveness, it becomes more imperative to develop appropriate infection control procedures to decrease the transmission of these organisms in the health care setting.

2. Antimicrobial resistance in Enterococci

The following agents have shown intrinsic resistance to enterococci:

1. Penicillin’s
2. Cephalosporins
3. Clindamycin
4. Aminoglycosides
5. Trimethoprim/sulfamethoxa-zole

The following agents have shown acquired resistance to enterococci:

1. Macrolides
2. Tetracycline
3. Lincosamides
4. Chloramphenicol
5. Aminoglycosides
6. Penicillin (without beta-lactamase)
7. Penicillin (with beta-lactamase)
8. Vancomycin
9. Quinolones

3. Reservoirs

Enterococci are normal inhabitants of the human gastrointestinal tract. Other major sites of colonization that may act as reservoirs for enterococci in hospitalized patients or nursing home residents include wounds and chronic decubital ulcers (pressure sores). Enterococci are seldom found in pure culture in wounds, but when they are, the wounds usually have no clinical evidence of infection. Generally, enterococci are present in mixed culture in soft tissue wounds. Asymptomatic women may also carry enterococci in high numbers in their vaginas, while 60% of men in hospitals may carry enterococci in their perineal or meatal areas.

Health care providers may also become colonized with resistant enterococci and contribute to their spread by poor hygiene. Recently, the role of elderly patients residing in extended care facilities as sources of resistant enterococci has been addressed. In one VA medical center, several of the patients were colonized with resistant enterococci in their rectum or urine. These studies suggest that the community and extended care facilities may provide a continuous source for reintroduction of resistant enterococci (VRE) in hospitals.

4. Modes of transmission

Historically, the source of enterococcal infections was felt to be the patient’s own flora. Early studies suggested that enterococci isolated from infections were from the host’s own gastrointestinal tract. Possible environmental contamination may lead to the spread of the organism.
	Contact spread is the primary means of transmission by health care workers. This organism does not spread via respiratory droplets. Good handwashing practices must be part of the employee’s orientation program.

5. Risk factors

Early studies examining risk factors for the development of enterococcal urinary tract infections identified urinary tract instrumentation or catheterization, other genitourinary pathology, the previous use of antibiotics, especially cephalosporins, as significant risk factors. Imipenem was found to significantly predispose to acquisition of ampicillin-resistant enterococci, while previous use of vancomycin was important for acquiring vancomycin-resistant strains (i.e., treating MRSA colonized patients with vancomycin).

6. Pathogenesis

For the most part, enterococci are part of the human endogenous flora. However, in the elderly or immunocompromised patient, these organisms become opportunistic. For example, early studies showed that enterococci frequently colonized the meatus and perineum of hospitalized men, but infections developed predominantly when these men were catheterized or had genitourinary pathology. Little is known about the virulence factors in enterococci. There is a hemolysin factor (destroys red cells) which has been shown to contribute to the disease process. No other factors have been described.

7. Diseases

The types of diseases that enterococci can produce are as follows: urinary bacteremia/septicemia endocarditis intra-abdominal/pelvic infections skin and soft tissue neonatal infections meningitis (rare) otitis media with effusion lower respiratory (rare)

8. Prevention and risk reduction of nosocomial infections caused by enterococci

Enterococci are very tolerant organisms and can survive easily on the hands of health care personnel. Patient-to-patient spread by health care personnel has been documented. Strict observance of hand-washing policies would then be a key element in controlling the spread of epidemic strains of enterococci or any other organism.

Cohorting of infected and colonized patients with poor hygiene has been used to prevent the spread of this organism. Proper barriers such as gloves and gowns when soiling is likely are important in preventing dissemination.

Each health care facility through collaboration of its quality improvement and infection control programs such as pharmacy, reference microbiology laboratory, nursing, physicians, housekeeping services should develop a comprehensive, institutional-specific strategic plan to detect, prevent and control infection and colonization¹ with VRE.

Proper use of vancomycin is very important control measure. Situations in which the use of vancomycin is appropriate or acceptable are:

1. treatment of serious infections caused by beta-lactam gram-positive organisms;
2. treatment of infections caused by gram-positive microorganisms in patients/residents who have serious allergies to beta-lactam antibiotics;
3. when antibiotic-associated colitis (caused by Clostridium difficile) fails to respond to metronidazole therapy or is severe and potentially life-threatening.

______
¹An example of a microbiology report demonstrating a VRE isolate can be seen in Appendix A.

 

Situations in which the use of vancomycin should be discouraged:

1. treatment in response to a single blood culture positive for coagulase negative Staphylococcus;
2. continued empirical use for presumed infections in patients whose cultures are negative for beta-lactam resistant gram-positive organisms;
3. eradication of MRSA colonization;
4. primary treatment of antibiotic-associated colitis;
5. use of vancomycin solution for topical application or irrigation.

Key parameters of vancomycin use can be monitored through the reference pharmacy and can be part of the quality assurance/improvement process or as part of a drug-utilization review by the pharmacy.

The following measures should be implemented by all health care facilities:

1. reference laboratories should notify appropriate personnel that a vancomycin-resistant enterococcus has been isolated;

2. alert staff members that such an organism has been isolated from your facility;
3. establish systems(s) for monitoring appropriate process and outcome measures (e.g., cumulative incidence or incidence density of VRE colonization, rate of compliance with VRE isolation precautions and handwashing, interval between VRE identification by the laboratory and implementation of isolation precautions).

Initiate the following isolation precautions to prevent resident-to-resident transmission:

1. place VRE-infected residents (drainage can not be contained) in CONTACT ISOLATION (private room);
2. place known colonized residents with poor hygiene and with the possibility of spread high in a cohort system or a private room;
3. wear a gown when soiling is likely or if possibilities are unknown when entering a room;
4. wear gloves when entering a room; CDC advocates the use of gowns and gloves when entering the room.
5. remove gloves and gown before leaving room;
6. wash hands immediately - whether to use an antimicrobial soap is still controversial - it is not what you wash your hands with, it is when and how you wash your hands that is important. A good lotion soap is more than satisfactory. However, CDC advocates the use af an antimicrobial soap.
7. adopt a policy for deciding when the resident comes out of isolation or a cohort system;
8. any gross contamination of body fluids (e.g., fecal contamination) should be cleaned up as soon as possible with an EPA registered disinfectant to avoid environmental spread.

9. Educational programs

Continuing education programs for all physicians, nurses and pharmacists should be provided at least annually or as needed. The program should include information concerning the epidemiology of vancomycin- resistant enterococci and the potential impact that this organism has on the cost and outcome of resident care. The information should also be distributed to all personnel who have direct care with any patients or residents. Housekeepers and laundry personnel should also receive education at an appropriate level so that anxiety levels are not created.

10. Summation

Standard Precautions (formerly called Universal Precautions) when broadly interpreted (i.e., handwashing before and after all patient/resident contact, use of gloves for all body fluids and secretions/mucous membranes/non-contact skin; use of gowns if soiling is likely to occur and the use of protective eye-wear if splashing of body fluid is likely), are adequate to prevent the spread of VRE when these precautions are applied correctly and consistently.

References:

Vancomycin-resistant enterococci - highlights. KY Epidemiologic Reports. 29(10):3. 1994.

Enterococcus species. In: Hospital Epidemiology and Infection Control. Pp. 334-342. 1996.

Enterococcus species. In: APIC Infection Control and Applied Epidemiology. Pp. 57-1 - 57-5. 1996.

Recommendations for preventing the spread of vancomycin resistance. MMWR. 44: (RR-12):1-13. 1995.

Questions:

1. The enterococci are predominantly found in gut flora:

1. true
2. false

2. The enterococci are very sensitive to drying:

1. true
2. false

3. Meningitis is a common illness caused by the enterococci:

1. true
2. false

4. Risk factors responsible for enterococci infections are:

1. urinary tact instrumentation
2. previous use of antibiotics
3. genitourinary pathology
4. all of the above
5. none of the above

5. Little is known about the virulence factors of the enterococci:

1. true
2. false

6. The most common cause of disease by the enterococci are urinary tract infections:

1. true
2. false

7. Hand to hand transmission has never been demonstrated by the enterococci:

1. true
2. false

8. Treatment of choice for Clostridium difficile colitis is:

1. IV vancomycin
2. Oral vancomycin
3. Oral metronidazole
4. IV penicillin G
5. none of the above

9. IV vancomycin is the drug of choice for colonized patients with methicillin- resistant Staphylococcus aureus:

1. true
2. false

10. It has been established by CDC that healthcare workers entering a room with an infected VRE patient should be gloved and gowned:

1. true
2. false

11. Laboratories should always alert the staff that a VRE has been isolated as soon as possible (i.e., phone call):

1. true
2. false

12. Continuing education programs on VRE should include housekeeping personnel:

1. true
2. false

13. Common disinfectants that are normally used in health care (EPA registered) is more than satisfactory for cleaning rooms containing infected VRE patients:

1. true
2. false

14. Linens containing VRE drainage should be washed separately:

1. true
2. false

Answers:

1. a
2. b
3. b
4. d
5. a
6. a
7. b
8. c
9. b
10. a
11. a
12. a
13. a
14. b