Resource Packages: Vancomycin Resistant Enterococcus (VRE)

Historical Overview

For many years enterococci were viewed as relatively endogenous flora with little potential for human infection. Known originally as streptococcus faecalis, or Group D enterococcus, they are Gram Positive Cocci.

Enterococci were the first organisms to develop Vancomycin resistance. Vancomycin Resistant Enterococci (VRE) were first reported in Europe in 1988. Since then VRE strains have been identified in the USA with reported outbreaks of VRE infections (Enterococcus faecium or Enterococcus faecalis). Enterococci are now among the four most common nosocomial bacterial pathogens in the USA.

The view that enterococci were a relatively harmless bacteria resulted primarily because they were found as frequent normal inhabitants of the human gastrointestinal tract as well as non-pathogenic colonisers of the human oral cavity, the vagina and soft tissue wounds.

Enterococci were frequently isolated as part of mixed flora in intra-abdominal infections. Despite their apparent lack of virulence, the enterococci in recent years have emerged as important nosocomial pathogens. Although most isolates represent colonisation or minor infection, septicaemia and other serious invasive infection does occur and may be associated with fatalities.

Enterococci possess a number of significant characteristics that allow them to survive and cause serious infections in hospitalised patients, especially the critically ill or those with severe underlying disease or immunosuppression. These bacteria are intrinsically resistant to many antimicrobial agents commonly used in hospitalised patients. They have considerable ability to acquire resistance through exchange of genetic elements with other gram-positive cocci. They are a very hardy organism and can survive in the environment and on the hands of hospital personnel, hence the strict adherence to glove wearing and handwashing with an antiseptic agent.

Antibiotic-resistant enterococci can also colonise the gastrointestinal tract of health care workers and patients, providing a continuous reservoir for “in-hospital" spread. Once a patient is colonised the organism may persist for 12 months or more. Sampling in hospitals has found VRE in most parts of the environment. Outbreaks have been attributed to contamination from rectal thermometers, bedpans and hospital beds.

There has been a recent discovery of a S. aureus intermediately resistant to vancomycin (known by the acronym VISA).

Recent Trends

In many American hospitals infections are often fatal because they are incurable with standard antibiotics. Most clusters of VRE have been confined to single hospital units, but wider outbreaks have been described and spread of the organism between hospitals has been attributed to patient transfers.

In order to contain the spread of VRE, or ideally eliminate it altogether, a number of strategies need to be taken:

Standard Precautions and Contact Precautions should be practiced at all times
Contact Precautions are designed to reduce the risk of transmission of micro-organisms by direct of indirect contact. Contact Precautions require a single room, gowns/aprons
Handwashing is of particular importance in preventing the spread of VRE. Hands must be washed before and after all patient contacts
Disposable gloves either latex or vinyl must be used for contact with all patients and disposed of properly after each procedure before leaving the patient’s room

Infection Control Networks

Each hospital will need to design specific strategic plans to prevent, find and limit infection due to VRE. These initiatives should be coordinated by multidisciplinary infection control committees.

The microbiology laboratory plays a crucial role in that it must provide rapid, accurate identification of enterococci, detect patterns of resistance, and design and implement screening programs in consultation with the Infection Control Coordinator.

Enterococcal sepsis occurs most frequently in patients who are immunosuppressed or chronically or critically ill.

Infection control efforts should therefore focus on likely sites in the hospital where a resistant organism may arise:

Intensive Care Units
Oncology
Transplant Units
Renal Dialysis Units

Prevention and Control of VRE

Notify appropriate staff promptly when VRE are detected
Inform clinical staff of the hospital’s policies regarding patients infected or colonised with VRE (as per Infection Control Manual)
Establish systems to ensure control measures are effective
Institute Standard Precautions and Contact Precautions (as discussed above)
Dedicate non-critical items (eg stethoscopes) to a single patient or cohort of patients infected or colonised with the organism
Screen room mates of patients newly diagnosed with VRE (by stool culture or rectal swab)
Devise a policy of screening affected patients to determine when they can be removed from Contact Precautions
Establish a system to allow prompt identification of affected patients who are re-admitted so that segregation can occur
Develop strategies to be used during transfer of VRE infected or colonised patients to other health care facilities

Asymptomatic stool carriage is common, often lasting weeks or months, and may contribute to the spread of resistant strains into the community. Detection of this organism should raise awareness of clinical staff and prescribers and prompt greater vigilance.

Extra vigilance is required for patients with prolonged hospital stays complicated by the need for gastrointestinal surgery, indwelling catheters, central venous lines and prolonged courses of broad spectrum antibiotics.

Restriction of Antibiotic Use

The emergence of enterococci as pathogens is a symptom of the increasing use of cephalosporins in the hospital environment. Every effort must be made to restrict the use of Vancomycin. The most logical approach would be to limit the prescribing of broad spectrum antibiotics, especially Vancomycin.

All hospitals and health care facilities, even those where VRE has never been detected, should develop a comprehensive anti-microbial utilisation plan to provide education for their medical staff (including medical personnel rotating through health care facilities), oversee surgical prophylaxis and develop guidelines for the proper use of Vancomycin.

Hospital pharmacy committees in collaboration with such groups as the Australian Antibiotic Advisory Group, should have in place Restricted Antimicrobial Drug Dispensing policies and procedures. There is no evidence that Vancomycin is superior to ampicillin for the treatment of ampicillin susceptible enterococcal infections.

Acceptable indications for the use of Vancomycin would include:

Infection caused by methicillin-resistant staphylococci or ampicillin-resistant enterococci
Perioperative prophylaxis for prosthetic valve replacement or implantation of prosthetic vascular grafts
Only a single preoperative dose should be used. Vancomycin should NOT be continued for more than 24 hours following surgery

Future Implications

The emergence of multi drug-resistance enterococci could have a devastating clinical impact in Australia.

Guideline development should be part of the hospitals quality improvement program and especially involve participation from the hospital pharmacy and therapeutics committee, hospital epidemiologist, Infection Control, infectious diseases, medical and surgical staff as well as senior management staff.

Prevention and control of the spread of Vancomycin resistance will require a co-ordinated, concerted effort from various departments in all hospitals and can only be achieved with education, early detection and immediate implementation of appropriate infection control measures.

The high prevalence of colonisation and high rate of nosocomial acquisition of antibiotic-resistant enterococci poses the threat that clinical infections will become even more common. If the factors leading to colonisation with resistant enterococci are identified and then better controlled, it may be possible to decrease the incidence of clinical infection.

References

Heath C, Blackmore T, Gordon D. 1996, Vol 164, pp 116-120, Emerging Resistance in Enterococcus spp. Medical Journal of Australia.

Hospital Infection Control Practices Advisory Committee, 1995, Vol 16 No 2, pp 105 - 113, Recommendations for Preventing the Spread of Vancomycin Resistance. Infection Control Hospital Epidemiology, Atlanta, Georgia, USA.

Maki D. 1996, Vancomycin And Ampicillin-Resistant Enterococcus Faecium. University of Wisconsin Hospital and Clinics, Wisconsin, USA.

Mayhall G, Glen. 1996, Epidemiology and Infection Control. Williams and Wilkins, Baltimore, USA.

NSW Health Department, 1999, Infection Control Policy. 99/87, AIDS/Infectious Diseases Branch, Sydney.

Weinstein, Jeffrey W. et al. January 1996, 17: pp 36-41, Infection Control And Hospital Epidemiology, Resistant Enterococci: A Prospective Study of Prevalence, Incidence, and Factors Associated With Colonisation in a University Hospital. USA.

Wenzel RP, 1993, 2nd ed, Prevention and Control of Nosocomial Infections. Williams and Wilkins, Baltimore, USA.

This document is based on the Recommendations of the Hospital Infection Control Practices Advisory Committee (HICPAC)

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