Joan M Weber
RN BSN CIC
Infection Control Coordinator
Shriners Burns Hospital
Boston, USA
E: [email protected]
Infection in burn patients is a leading cause of morbidity and mortality and remains one of the most challenging concerns for the burns team. The importance of preventing infection has been recognised in organised burns care since its inception. Strategies for infection prevention and control, including guidelines for culturing and surveillance, isolation of patients, environmental concerns and use of antibiotics will be discussed.
Epidemiology of infection
The development of infection depends on a source of organisms, a mode of transmission and the susceptibility of the patient. Infection risk for burn patients is different from other patients in several important respects. Sources of organisms are found in the patient’s own endogenous (normal) flora, exogenous sources in the environment and in healthcare personnel. Exogenous organisms from the hospital environment are generally more resistant to antimicrobial agents than endogenous organisms. Organisms associated with infection in burn patients include Gram-positive, Gram-negative and yeast/fungal organisms.
Gram-positive organisms of particular concern include methicillin-resistant S aureus (MRSA), vancomycin-resistant enterococci (VRE) and the potential development of vancomycin-resistant S aureus. MRSA has become an endemic organism in many burns units. It has been argued that no extraordinary efforts be made to control its spread; however, this view has been increasingly challenged in the era of VRE. With the increasing incidence of VRE in hospitals, the risks associated with infection with this organism are also increasing. Risk factors identified in patients colonised with VRE include one or more of the following: prior vancomycin use, prior use of third-generation cephalosporins and antibiotics active against anaerobes, a critically ill patient with severe underlying disease or immunosuppression, and a prolonged hospital stay. These factors are all present in patients with a large burn injury, including previous vancomycin use in units with a high endemic rate of MRSA.
Gram-negative organisms have long been known to cause serious infection in burn patients. Gram-negative bacteraemia has been associated with a 50% increase in predicted mortality for patients with bacteraemia compared to those without bacteraemia.(1) At present, Gram-negative organisms such as P aeruginosa and A baumannii that are resistant to multiple antibiotics are of particular concern in both burns units and elsewhere in the hospital. Fungal organisms, especially Candida (yeast) species and true fungi (mould) like Aspergillus, Mucor and Rhizopus have been associated with serious infection in burn patients. Candida colonisation appears to be primarily from endogenous sources while true fungi are ubiquitous in the environment. They can be found in air handling and ventilation systems, plants and soil.
Modes of transmission include contact, droplet and airborne spread. In burn patients the primary mode is direct or indirect contact, either from the hands of the personnel caring for the patient or contact with inappropriately decontaminated equipment. Burn patients are unique in their susceptibility to colonisation from organisms in the environment as well as in their tendency to disperse organisms into the surrounding environment. In general, the larger the burn injury, the greater the volume of organisms that will be dispersed into the environment from the patient.
The patient has three principal defences against infection: physical defences, nonspecific immune responses and specific immune responses. Changes in these defences determine the patient’s susceptibility to infection.
Invasive devices, such as endotracheal tubes, intravascular catheters and urinary catheters bypass the body’s normal defence mechanisms. Infection from intravascular catheters is of particular concern for burn patients because these lines must be placed directly through or near burn-injured tissue. Catheter-associated bloodstream infection (BSI) is caused by organisms that migrate along the catheter from the insertion site and colonise the catheter tip.(2) Catheter tips are also susceptible to colonisation from haematogenous seeding of organisms from the affected burn wound.
Incidence of infection
Incidence of infection is also affected by the size of the patient’s burn injury. The overall incidence of infection is low for patients with smaller (<30% total body surface area [TBSA]) burn injuries and generally associated with the need for invasive devices. Invasive burn wound infection is rarely seen. When it occurs it is usually in patients with larger (≥30% TBSA) burn injury. BSI increases dramatically as burn wound size increases, related to increased exposure to intravascular catheters and to burn wound manipulation-induced bacteraemia. Pneumonia occurs most frequently in ventilated patients and urinary tract infection (UTI) occurs principally in patients with indwelling urinary catheters.
Outbreaks on burn units
Outbreaks of cross-colonisation and infection are a major challenge in burn units. They require a clear understanding of how and why they occur in order to prevent or control them. The exact cause for many of these outbreaks cannot be determined. However, certain patterns are clear.
In almost all cases the colonised patient is thought to be a major reservoir for the epidemic strain. Other important sources include contaminated hydrotherapy equipment, common treatment areas and contaminated equipment (eg, mattresses), which appear to pose unique risks of cross contamination in the burn environment. Risks associated with caring for the burn wound, such as hydrotherapy and common treatment rooms, are related to the use of water sources that are frequently contaminated by Gram-negative organisms intrinsically, and may also be contaminated by organisms from other patients.(3) This aquatic environment is difficult to decontaminate because of continuous reinoculation of organisms from the patients’ wound flora and the organisms’ ability to form a protective glycocalyx in water pipes, drains, and other areas – making them resistant to the actions of disinfectants.
The risks associated with a “common treatment room” involve the contamination of the surrounding environment and the difficulty in ensuring that the room is appropriately cleaned between successive patients. This is difficult given the number of procedures performed each day and the necessity of stocking the room with dressing supplies for multiple patients. For patients at increased risk of infection – those with 30% burn or greater, or those with invasive devices – hydrotherapy and common treatment rooms should be used cautiously, if at all. If dressings can be changed at the patient bedside, this is preferable to exposing these patients to the risks of common treatment rooms or hydrotherapy.
The other principal modes of transmission in burn units are by the hands of the personnel and through contact with inadequately decontaminated equipment or surfaces. The hands and apron area of the carer are most likely to become contaminated, as the surfaces (ie, beds, side rails, tables and equipment) are often heavily contaminated with organisms from the patient. Likewise all equipment used on the patient (ie, blood pressure cuffs, thermometers, wheelchairs and IV pumps) are also heavily contaminated and may be transmitted to other patients if strict barriers are not maintained and appropriate decontamination carried out. In fact, a single cause is uncommon in a burn unit outbreak; in almost all instances, multiple factors contribute to its occurrence and perpetuation.
Culturing and surveillance
Culturing and surveillance guidelines are more stringent for the burn patient, particularly the patient with larger injuries, because of the increased propensity for transmission and infection in this population. The purposes of obtaining routine surveillance cultures are:
- To monitor the effectiveness of current wound treatment.
- To guide perioperative or empiric antibiotic therapy.
- To detect any cross-colonisations that occur quickly in order to prevent further transmission.
Wound cultures should be obtained for routine surveillance when the patient is admitted and at least weekly until the wound is closed. Many burn centres recommend obtaining wound cultures two or three times a week for patients with large burn injuries. Admission cultures are particularly important for patients transferred from other facilities, as they may be colonised with multiply resistant organisms and serve as an unsuspected reservoir for cross-transmission to other patients in the unit.
Surveillance of infection has been shown to diminish the rate of nosocomial infection as well as reduce costs related to length of hospitalisation, isolation and the need for antibiotic therapy. (4,5,6,7) Surveillance of infection in burn patients should be done to monitor incidence and rates, which have been appropriately risk-adjusted by the size of burn injury and invasive device use. At a minimum, surveillance should include collection of data on burn wound infection, urinary tract infection, pneumonia and BSI. Systematic collection of data allows the burn unit to monitor changes in infection rates over time, identify trends and evaluate current treatment methods.
Isolation guidelines
Standard precautions should be followed when caring for all patients with burn injury. The effectiveness of simple protective barrier precautions in reducing nosocomial colonisation and infection was shown in a study by Klein et al in a paediatric intensive care unit (ICU).(8) Most burn units also supported the concept of barrier techniques and isolation. The open burn wound increases the environmental contamination present around the patient, which is the major difference between burn and nonburn patients.
Patients with greater than 30% TBSA burn injuries are more immunocompromised, due to the larger size of their injury. In combination with their loss of physical defences and need for invasive devices, this significantly increases their risk of infection. There is also a major risk of these patients contaminating their environment with organisms, which may then be spread to other patients on the unit. These may include multiply resistant organisms, if broad-spectrum antibiotic treatment has been required to treat infectious complications. For these reasons, it is recommended that patients with larger burn injuries are isolated in private rooms or other enclosed bed spaces to ensure physical separation from other patients. Such isolation has been associated with a decrease in cross-transmission of organisms.(9,10)
Special attention is also required for patients with smaller burn injuries who are colonised or infected with multiply resistant organisms such as MRSA, VRE or multiply resistant Gram-negative organisms. This is especially true for patients with wound drainage that cannot be adequately contained in dry, occlusively wrapped outer dressings or paediatric patients who cannot comply with hand washing or other precautions. Patients transferred to the burns unit after treatment in another hospital should also be included in this group until the results of their admission cultures are known. These patients are frequently colonised with resistant organisms and may serve as an unsuspected reservoir for transmission to other patients unless they are isolated. Isolation for this group of patients generally includes placement in a private room on contact precautions, with the addition of droplet precautions in some circumstances.
Patients colonised with multiply resistant organisms must frequently have their need for isolation balanced against their need for rehabilitation. In general, if the patient’s wound cannot be occlusively wrapped in a dry outer dressing, the patient should not be taken to the rehabilitation department for therapy when other patients will be present in the same area. If rehabilitation needs cannot be met in the patient’s room, then sufficient time should be scheduled in the rehabilitation department to allow for the patient’s treatment followed by thorough cleaning of all equipment and surfaces before the area is used by other patients. The rehabilitation therapy staff should wear appropriate attire during therapy.
Environmental issues
Disinfection and sterilisation guidelines for patient care equipment must take into account the presence of extensive, open wounds – the major distinction separating this group from other patient populations. Following Spaulding’s scheme for categorising patient care items and equipment, the changes for the burn patient population involve “semicritical” and “noncritical” items.(11) Many items, such as blood pressure cuffs, stethoscopes and bedpans – if used on areas without dry, occlusive dressings – may need high-level disinfection as a semicritical item or may need to be restricted to an individual patient.
Plants and flowers should not be allowed in units with burn patients because they harbour Gram-negative organisms, such as Pseudomonas species, other enteric Gram-negative organisms and fungi. Many of these organisms are intrinsically resistant to multiple antibiotics, which may serve as reservoirs to colonise the burn wound.(12)
Paediatric burn patients should also have policies restricting the presence of non-washable toys such as stuffed animals and cloth objects. These can harbour large numbers of bacteria and are difficult to disinfect. Toys should be nonporous and washable, designated for individual patient use. They should be thoroughly disinfected after use and before being given to another child. Paper items, such as storybooks and colouring books, should always be designated for a single patient’s use. They should be disposed of if they become grossly contaminated or when the child is discharged.
Antimicrobials and burns
Systemic antimicrobial treatment must be thoughtfully considered in the care of burn patients to prevent the emergence of resistant organisms. The burn wound will always be colonised with organisms until wound closure is achieved. Administering systemic antimicrobials will not eliminate this colonisation, but promote the emergence of resistant organisms. If antimicrobial therapy is indicated to treat a specific infection, it should be tailored to the specific susceptibility patterns of the organisms as soon as this information is available.
Conclusion
Many questions have yet to be answered for the burn patient in relation to appropriate management of infection control issues. The use of invasive devices, in particular central venous catheters, should be re-evaluated in light of the new catheter technologies and improved wound management techniques.
An important area for future study relates to the clinical problem of appropriate precaution strategies, particularly for patients colonised with multiply resistant organisms. The goal should be identifying cost-effective measures that prevent outbreaks involving other patients on the unit. Currently, there is wide variation in precautions for burn patients, with no agreed upon standards followed in most burn centres. In an era of changing healthcare priorities, studies are also needed to evaluate the efficacy of caring for burn patients outside the burns centre or of caring for non-burn patients in the burns centre. The impact that burn patients will have on existing infection rates and infectious complications must be integral to decisions and the effect these decisions will have on costs, patient outcomes and patient satisfaction.
Resources
International Society for Burn Injuries
W: www.worldburn.org
American Burn Association
W: www.ameriburn.org
European Burns Association
W: www.euroburn.nl
References
- Mason AD Jr. McManus AT, Pruitt BA Jr. Association of burn mortality and bacteremia: a 25-year review. Arch Surg 1986;121: 1027-31.
- Goldman DA and Pier GB. Pathogenesis of infection related to intravascular catheterization. Clin Microbiol Rev 1993,6:176-92.
- Weber JM.Epidemiology of infections and strategies for control. In: Carrougher GJ, editor. Burn care and therapy. St Louis: Mosby; 1998 p. 185-211.
- Haley RW, Culver DH, White JW, et al. The efficacy of infection surveillance and control programs in preventing nosocomial infections in US hospitals. Am J Epidemiol 1985;121:182 -205.
- Nichols RL. Surgical wound infection. Am J Med 1991;91 Suppl 3B:54S-64S.
- Condon RE, Schulet WJ, Malangoni MA, et al. Effectiveness of a surgical wound surveillance program. Arch Surg 1983;118:303-7.
- Olsen MM, Lee JT. Continuous 10-year wound infection surveillance: results, advantages, and unanswered questions. Arch Surg 1990;125:794-803.
- Klein BS, Perloff WH, Maki DG. Reduction of nosocomial infection during pediatric intensive care by protective isolation. N Engl J Med 1989;320:1714-21.
- Burke JF, Quinby WC, Bondoc CC et al. The contribution of a bacterially isolated environment to the prevention of infection in seriously burned patients. Ann Surg 1977;186: 377-87.
- McManus AT, McManus WF, Mason AD Jr, et al.Microbial colonization in a new intensive care burn unit. Arch Surg 1985;120:217-23.
- Rutala WA.Disinfection and sterilization of patient care items. Infect Control Hosp Epidemiol 1996;17:377-84.
- Kates SG, McGinley KJ, Larson EL, et al. Indigenous multiresistant bacteria from flowers in hospital and nonhospital environments. Am J Infect Control 1991;19:156-61.
