Elsevier

Burns

Volume 33, Issue 3, May 2007, Pages 341-346
Burns

Correlation of culture with histopathology in fungal burn wound colonization and infection

https://doi.org/10.1016/j.burns.2006.08.040Get rights and content

Abstract

An increasing number of burn wound infections are now due to fungi. Historically, therapy of fungal burn wound infections (FWI) consisted of debridement, topical antifungals and/or IV amphotericin B, negating the need to categorize disease further than fungal burn wound colonization (FWC) versus FWI. Newer antifungal agents have varying spectrums of activity, increasing the importance of identifying fungi, often to species. The records of patients admitted to our burn center from April 2000 to March 2005 were reviewed for fungi identified by histopathology. Wound specimens with fungi were classified as FWC or FWI and culture results were compared. The 1515 surgical wound tissue specimens were obtained from 2036 patients. Fungi were detected in the histopathology of 68 patients, 19 with FWI (3.8 FWI/year); 9 had corresponding growth on culture. Forty nine patients were identified with FWC, 16 with fungi recovered in corresponding cultures. FWI was associated with increased mortality (OR 25.3, CI 3.12–204.8). Correlation between histopathologic and culture identification of fungi was inconsistent. The etiology of FWI was diverse; fungi with known resistance to each of the three major classes of antifungals were isolated, suggesting empirical use of one class may be inadequate to treat FWI. Future burn wound management must seek to identify fungal pathogens to species.

Introduction

Burn wound infections remain an important source of morbidity and mortality in burn centers. In the past, the predominant pathogens were bacterial, but with advancements in burn wound care and the introduction of topical mafenide in 1964, the epidemiology of burn wound infections has shifted such that fungal pathogens are now more common. In the years subsequent to the introduction of mafenide (1964–1969), the United States Army Institute of Surgical Research (USAISR) noted a four-fold increase in incidence of fungal burn wound infections (FWI) [1]. In a follow on study, this trend continued with the yearly incidence of bacterial wound infections decreasing while the incidence of FWI remained unchanged [2]. During this second time period fungi represented the most common burn wound pathogens.

Recovery of fungi in culture from wounds can be difficult. In the past, identification to genus and species was of limited importance, as therapy consisted mainly of surgical intervention and intravenous amphotericin B (or topical antifungal compounds). FWI have previously been identified and classified by wound histopathology. The introduction of systemically available azoles (fluconazole and itraconazole), and more recently, the broad-spectrum azole voriconazole and the echinocandins (anidulafungin, caspofungin and micafungin), has greatly impacted the treatment of fungal infections in general. The newest of these agents are effective against a wide range of fungi; however, none of them cover all potential pathogens (Table 1). Although amphotericin B still has the broadest spectrum of all antifungal agents, these newer agents do provide coverage against several fungi that are not typically responsive to amphotericin B (e.g., Pseudallescheria boydii and Aspergillus terreus).

Identification of the genus (and often species) causing FWI has become important for patient care, as no one agent can provide adequate empirical therapy in all infected patients. Herein, we review and compare the culture recovery and histopathological diagnosis of FWI and fungal burn wound colonization (FWC) at our institution over a 5-year period to examine the correlation between these methods and its impact (or potential impact) on selection of antifungal therapy.

Section snippets

Methods

All patients admitted to the USAISR burn center from April 1, 2000 to March 30, 2005 were identified. Electronic medical records, the USAISR research database, and histopathology reports were reviewed to select those patients with FWC or FWI. For those identified, demographic details were collected, including age, sex, total body surface area (TBSA) burn and select comorbidities (diabetes mellitus, hypertension, malignancy, alcohol abuse). Survival to discharge or death was also recorded for

Results

During the period from April 1, 2000 to March 30, 2005, 2036 patients were admitted to the USAISR burn center. Of 1515 surgical specimens examined by histopathology, 68 contained fungi, 19 of which were consistent with a diagnosis of FWI (3.8 FWI/year) (Table 2). This represents an incidence of FWI of 0.69 per 1000 hospital days or 12.1 per 1000 discharges during the defined study period. Over the study period, the incidence of FWI ranged from 1 to 5 per year, with per 1000 hospital day rates

Discussion

Fungal wound infections remain an important source of morbidity and mortality in burn units. In an early case series of 30 patients admitted to this institute from 1954 to 1970, there was a 50% overall mortality with a 30% attributable mortality for invasive fungal infections [4]. A later review from the USAISR reviewed cases of fungal burn wound infections from 1973 to 1977. Mortality was 83% in those treated for invasive candidal infections and 87% for treated non-candidal invasive fungal

Conclusion

With the expanding armamentarium of antifungal agents with differing spectrums of activity it is becoming increasingly important to correlate wound histopathology with corresponding cultures. Our study highlights that histopathology alone is often inadequate for determining the best antifungal agent as the histopathology-to-culture correlation was poor. As the fungi involved in FWI are common normal flora or environmental contaminants, the role of confirming infection with histopathology

Acknowledgements

The authors would like to thank Dr. Mark Rasnake for his help with the statistical analysis.

Disclaimer: The views expressed herein are those of the authors and do not reflect the official policy or position of the Department of the Air Force, Department of the Army, Department of Defense or the US Government. The authors are employees of the US government. This work was prepared as part of their official duties and, as such, there is no copyright to be transferred.

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This work was presented in part at the 43rd Annual Meeting of the Infectious Diseases Society of America, San Francisco, CA, October 7, 2005.

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