Viral Infections in Burn Patients: A State-Of-The-Art Review

Infections that are triggered by the accompanying immunosuppression in patients with burn wounds are very common regardless of age. Among burn patients, the most frequently diagnosed infections include the bacterial ones primarily caused by Pseudomonas aeruginosa or Klebsiella pneumonia, as well as fungal infections with the etiology of Candida spp. or Aspergillus spp. Besides, burn wounds are highly susceptible to viral infections mainly due to the impaired immune responses and defective functions of the immune cells within the wound microenvironment. The most prevalent viruses that invade burn wounds include herpes simplex virus (HSV), cytomegalovirus (CMV), human papilloma virus (HPV), and varicella zoster virus (VZV). Likewise, less prevalent infections such as those caused by the orf virus or Epstein-Barr Virus (EBV) might also occur in immunosuppressed burn patients. Viral infections result in increased morbidity and mortality rates in severely burned patients. Additionally, a positive correlation between the hospitalization duration and the severity of the viral infection has been demonstrated. Viral infections trigger the occurrence of various complications, ranging from mild symptoms to even fatal incidents. Accurate detection of viral infection is of great clinical importance because of the possibility for a quicker introduction of proper treatment therapy and shortening of hospitalization time. The aim of this paper is to provide a comprehensive review of the literature and summarize the findings regarding the most common viral infections in immunosuppressed burn patients.

Cytomegalovirus Colitis in a Burn Patient

The prevalence of cytomegalovirus in the burn population is high. However, its role in the clinical management of burn patients is still being defined. This report documents a 41-year-old man who developed cytomegalovirus (CMV) colitis after being admitted with a 72% burn. Before the administration of ganciclovir, the authors had difficulty controlling his quantitative wound cultures with serial debridements, topical agents, and systemic antibiotics for known pathogens, which led to graft loss. After the ganciclovir was given, his quantitative wound cultures improved without changing the authors' topical agents or systemic antibiotics and had improved graft take. Whether CMV infection alone contributed to an increased morbidity in this patient or the combination of bacteria/fungal infection with CMV led to a synergistic effect is still not clearly understood. CMV may have contributed to a dysfunction in his cell mediated immunity, which, in turn, lowered the bacterial and fungal load necessary to cause graft loss. Patients who continue to do poorly despite adequate treatment for known pathogens may need to be screened for CMV and treated.

Human herpes viruses in burn patients: A systematic review

OBJECTIVE

The contribution of human herpes viruses, including herpes simplex virus (HSV), cytomegalovirus (CMV), and varicella zoster virus (VZV) to morbidity and mortality after burns remains controversial. This systematic review was undertaken to assess evidence of herpes virus-related morbidity and mortality in burns.

MATERIALS AND METHODS

PubMed, Ovid, and Web of Science were searched to identify studies of HSV, CMV, or VZV infections in burn patients. Exclusion criteria included: A level of evidence (LoE) of IV or V; nonhuman in vivo studies; and non-English articles. There was no limitation by publication date.

RESULTS

Fifty articles were subjected to full-text analysis. Of these, 18 had LoE between I-III and were included in the final review (2 LoE I, 16 LoE II-III). Eight had a prospective study design, 9 had a retrospective study design, and 1 included both.

CONCLUSIONS

No direct evidence linked CMV and HSV infection with increased morbidity and mortality in burns. Following burn, CMV reactivation was more common than a primary CMV infection. Active HSV infection impaired wound healing but was not directly correlated to mortality. Infections with VZV are rare after burns but when they occur, VZV infections were associated with severe complications including mortality. The therapeutic effect of antiviral agents administered after burns warrants investigation via prospective randomized controlled trials.

Resistant pathogens, fungi, and viruses

Although originally described in Staphylococcus aureus, resistance among bacteria has now become a race to determine which classes of bacteria will become more resistant. Availability of antibacterial agents has allowed the development of entirely new diseases caused by nonbacterial pathogens, related largely to fungi that are inherently resistant to antibacterials. This article presents the growing body of knowledge of the herpes family of viruses, and their occurrence and consequences in patients with concomitant surgical disease or critical illness. The focus is on previously immunocompetent patients, as the impact of herpes viruses in immunosuppressed patients has received thorough coverage elsewhere.

Cytomegalovirus and burns: current perceptions, awareness, diagnosis, and management strategies in the United States and Germany

Trauma and immunosuppressed patients are at risk for cytomegalovirus (CMV) disease. Attributing pathogenicity in burn patients remains difficult and controversial because data are sparse. In this work, we surveyed U.S. and German burn centers and evaluated them for awareness, perceptions, diagnosis, and treatment of CMV in patients with burn injury. A total of 58% German (G) and 21% U.S. centers responded. CMV infection incidence was 1:280 G and 1:870 U.S. A total of 41% G and 78% U.S. burn centers considered CMV to be of minor importance and 41% G and 13% U.S. centers considered CMV to be of significant importance. A total of 70% G and 97% U.S. centers performed no admission screening. When testing, 70% G and 19% U.S. centers used serology; 52% G and 25% U.S. centers used body fluid viral isolation; and 43% G and 6% U.S. centers used leukocyte CMV-DNA analysis. A total of 72% G and 48% U.S. centers distinguished infection from disease. Human CMV disease was diagnosed by CMV-DNA (82% G, 19% U.S.), direct virus isolation (43% G, 13% U.S.), or RNA detection (26% G, 0% U.S.). A total of 43% G and 19% U.S. would treat the established disease. Establishing consistent guidelines for screening, diagnosis, and treatment seems prudent in caring for the immunocompromised burn patient.

Cytomegalovirus infection in burns: a review

Sepsis is responsible for significant morbidity and mortality in patients suffering from severe burn injuries. Burn patients are known to be immunocompromised, and it is generally accepted that the immunosuppressed patient may experience human cytomegalovirus (HCMV) infection and disease. Review of the very limited available literature identifies a seroconversion rate of between 18 and 22% for burn patients who were seronegative for HCMV prior to suffering their burn injury. Furthermore, approximately 50% of HCMV antibody-positive patients may reactivate. Blood products and allografted skin have clinically been identified as possible sources of HCMV transmission in burn patients. Experience in the treatment of infection or disease in burn patients is very scarce and limited to immunoglobulin therapy. Animal experiments have demonstrated that murine cytomegalovirus (MCMV)-seropositive skin grafts are able to infect immunodeficient mice as well as burned mice. Murine studies have also demonstrated that infection with MCMV enhances susceptibility to secondary bacterial infection and increases mortality in these animals. Burned mice challenged with MCMV have a significantly higher level of bacterial translocation to mesenteric lymph nodes than either control thermally injured mice without MCMV inoculation or non-burned mice injected with MCMV alone. In summary, it remains controversial whether HCMV infection per se alters outcome for the majority of burn patients. Subgroups of severely burned, seronegative patients may benefit from blood products and skin from seronegative donors. Antiviral strategies are not yet evaluated for the burn patient. Further investigations utilizing modern diagnostic techniques seem necessary.

Human cytomegalovirus infection of a severe-burn patient: evidence for productive self-limited viral replication in blood and lung

To date, only seroepidemiological data are available on the role of human cytomegalovirus (HCMV) in patients with severe burns. We present the first longitudinal analysis of disseminated HCMV infection with a demonstration of self-limited productive viral replication identified in both the blood and lung of a burn patient.

Occult herpes family viral infections are endemic in critically ill surgical patients

OBJECTIVE

Herpes family viruses have been recognized as pathogens for many years in immunosuppressed transplant or human immunodeficiency virus patients, but they have garnered little attention as potential pathogens in the nonimmunosuppressed critically ill. The objective of this study was to define the prevalence of and risk factors for development of herpes family virus infection in chronic critically ill surgical patients.

DESIGN

Prospective epidemiologic study.

SETTING

A 38-bed surgical intensive care unit in a major university hospital.

PATIENTS

Nonimmunosuppressed intensive care unit patients in intensive care unit for >/=5 days.

INTERVENTIONS

None; patients received no antiviral treatment during the study.

MEASUREMENTS AND MAIN RESULTS

Weekly cultures for cytomegalovirus (CMV) and herpes simplex virus, viral serologies, and T-cell counts were performed. The prevalence (95% confidence interval) of positive respiratory cultures for herpes simplex or CMV was 35% (22-49%); 15% (5-25%) cultured positive for CMV, 23% (11-35%) cultured positive for herpes simplex virus, and one patient's respiratory secretions culturing positive for both CMV and herpes simplex virus. The prevalence of CMV viremia was only 5.8% (1-10%). CMV+ patients had longer hospital admissions, intensive care unit admissions, and periods of ventilator dependence than CMV- patients, despite having comparable severity of illness scores. CMV+ patients also had significantly higher numbers of blood transfusions, prevalence of steroid exposure, and prevalence of hepatic dysfunction, and all were immunoglobulin G positive at the beginning of the study. In contrast, herpes simplex virus-positive patients had lengths of hospital admissions, lengths of intensive care unit admissions, and periods of ventilator dependence comparable with patients without viral infections (p >.05).

CONCLUSIONS

There is a significant prevalence (22-49%) of occult active herpes family viruses in chronic critically ill surgical patients. The clinical significance of these viral infections is unknown, although CMV+ patients have significantly higher morbidity rates than CMV- patients. Several factors suggest pathogenicity, but further study is needed to define causality.

Viral Infections and Wounds

The effects of viral infections on normal wound healing are discussed. The case report presented suggests that viruses can have a detrimental effect on the normal wound healing process.

Early but not late burn wound excision partially restores viral-specific T lymphocyte cytotoxicity

OBJECTIVE

Early burn wound excision restores immunocompetence and improves patient survival, but the exact mechanisms have not yet been defined. Burn injury impairs cytotoxic T lymphocyte (CTL) activity as a function of burn size, increasing the risk of infection. The purpose of this study was to determine if early wound excision improved viral-specific CTL function.

METHODS

Anesthetized C57BL/6 mice (n = 20) received 0%, 20%, or 40% total body surface area full-thickness contact burns and were inoculated 3 days later with intraperitoneal lymphocytic choriomeningitis virus. Eight days after infection, or 11 days after burn, CTL effectors (E) were harvested and tested against infected, radiolabeled L-Dh targets (T) in a 51Cr-release assay, at varied E:T ratios. Dilution curves of CTL activity were compared by analysis of variance. In the second experiment, mice (n = 18) underwent a 30% burn that was totally excised and grafted on postburn days (PBDs) 0, 3, and 7. Control groups included sham burn and no excision of a 30% burn. In the third experiment, mice (n = 22) received a 30% burn that was partially, completely, or not excised on PBD 3. Control groups included sham burn with and without excision. All groups were infected with intraperitoneal lymphocytic choriomeningitis virus on PBD 3. Viral-specific CTL activity was determined on PBD 11.

RESULTS

Both 20% and 40% burn injury impaired viral-specific CTL function. Wound excision on PBDs 0 and 3, but not on PBD 7, partially restored CTL function. Total excision of the 30% burn improved CTL activity to a greater extent than did partial excision.

CONCLUSION

Burn injury inhibits viral-specific CTL activity. Early, complete wound excision augments CTL function. Improved CTL activity after burn may reduce the risk of infection, providing an immunologic rationale for expeditious wound excision.

The changing epidemiology of infection in burn patients

Topical chemotherapy, prompt excision, and timely closure of the burn wound have significantly reduced the occurrence of invasive burn wound infection and its related mortality. Since wound protection is imperfect and invasive wound infection may still occur in patients with massive burns in whom wound closure is delayed, scheduled wound surveillance and biopsy monitoring are necessary to assess the microbial status of the burn wound and identify wound infections caused by resistant bacteria or non-bacterial opportunists at a stage when therapeutic intervention can control the process. As a reflection of the systemic immunosuppressive effects of burn injury, infection remains the most common cause of morbidity and mortality even though the occurrence of wound infections has been significantly decreased. Pneumonia is the most frequent infection occurring in burn patients today but the improvements in patient management, wound care, and infection control have made bronchopneumonia the most common form of this infection and gram-positive organisms the most common causative agents. The organisms causing bacteremia that exert a species specific effect on the mortality related to extent of burn injury and patient age have changed in concert with changes in wound flora. Infection control procedures, including scheduled surveillance cultures, utilization of cohort patient care methodology, strict enforcement of patient and staff hygiene, and patient monitoring have been effective in eliminating endemic resistant microbial strains, preventing the establishment of newly introduced resistant organisms, diagnosing infection in a timely fashion, instituting antibiotic and other necessary therapy in a prompt manner, and documenting the effectiveness of present day burn patient care and the improved survival of burn patients.