Laboratory Studies
Diagnosis of wound infection should focus on a careful physical examination that is performed frequently by personnel trained in the management of burns.
Laboratory tests or changes in laboratory values such as WBC count, neutrophil percentage, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) level are of low yield in detecting or predicting burn infections because of the inflammatory response associated with the burn itself.[4]
Diagnosis relies on clinical examination as outlined above (see Clinical) and culture data, including the following:
- Quantitative biopsy can be used to confirm infection but is not reliable. This procedure is useful in identifying the infecting pathogen.
- Quantitative swab is of limited value but may aid in identifying the infecting pathogen.[5]
- Tissue histopathology allows for quantification and evaluation of infection depth and involvement of non-burned skin.
The use of routine wound cultures as part of surveillance procedures has been proposed to provide early identification of organisms colonizing the wound, to monitor response to therapy, to guide empiric therapy, and to evaluate for nosocomial transmission. However, this has not been shown to improve patient outcomes, and routine application has been brought into question.
Imaging Studies
No imaging studies have been identified as useful for detecting wound infections.
Procedures
Multiple biopsy samples from several areas of the burn wound should be obtained and sent for histopathology and microbiological workup of the pathogens and their resistance profiles.
After cleaning the wound with isopropyl alcohol, 2 parallel incisions 1-2 cm in length and 1.5 cm apart with a depth to obtain a portion of the underlying fat are made in the skin. Alternatively, biopsy samples typically weighing 0.02-0.5 g may be obtained with a 3-mm punch-biopsy technique.
Biopsy is a commonly bypassed procedure because of technical difficulty within the microbiology section working up these types of samples or a lack of local histopathological expertise.
Histologic Findings
Bacteria are detected using Gram stain.
Fungus are detected based on standard morphological appearance on various stains (periodic acid-Schiff [PAS] and Gomori methenamine silver [GMS]), but cultures must be obtained to definitively identify the pathogen.
- Aspergillus -like morphology - Presence of parallel-walled, branching, septate hyphae (eg, Aspergillus species, Fusarium species, Phaeohyphomycetes)
- Mucor -like morphology (zygomycosis/mucormycosis) - Presence of wide, ribbonlike, rarely septate hyphae (eg, Rhizopus, Mucor, Rhizomucor, Absidia)
- Yeastlike morphology - Presence of budding yeasts or rounded, yeastlike structures (Many yeasts, including most Candida species also produce hyphae and pseudohyphae in tissue.)
Virus: Herpes simplex virus can be isolated via identification of inclusions on light or electron microscopy or other viral particles on biopsy specimen or lesion scrapings.
Staging
The various stages used to diagnose burn wound infections are as follows:
- Stage I - Colonization
- Superficial - Microorganisms present only on burn wound surface
- Penetrating - Variable depth of microbial penetration of eschar
- Proliferating - Variable level of microbial proliferation at nonviable–viable tissue interface (subeschar space)
- Stage II - Invasion
- Microinvasion - Microorganisms present in viable tissue immediately subjacent to subeschar space
- Deep invasion - Penetration of microorganisms to variable depth and expanse within viable subcutaneous tissue
- Microvascular involvement - Microorganisms within small blood vessels and lymphatics (thrombosis of vessels is common)
Latenser BA, Miller SF, Bessey PQ, Browning SM, Caruso DM, Gomez M, et al. National Burn Repository 2006: a ten-year review. J Burn Care Res. Sep-Oct 2007;28(5):635-58. [Medline].
Pidcoke HF, Wade CE, Wolf SE. Insulin and the burned patient. Crit Care Med. Sep 2007;35(9 Suppl):S524-30. [Medline].
Horvath EE, Murray CK, Vaughan GM, Chung KK, Hospenthal DR, Wade CE, et al. Fungal wound infection (not colonization) is independently associated with mortality in burn patients. Ann Surg. Jun 2007;245(6):978-85. [Medline].
Murray CK, Hoffmaster RM, Schmit DR, Hospenthal DR, Ward JA, Cancio LC, et al. Evaluation of white blood cell count, neutrophil percentage, and elevated temperature as predictors of bloodstream infection in burn patients. Arch Surg. Jul 2007;142(7):639-42. [Medline].
Uppal SK, Ram S, Kwatra B, Garg S, Gupta R. Comparative evaluation of surface swab and quantitative full thickness wound biopsy culture in burn patients. Burns. Jun 2007;33(4):460-3. [Medline].
Ong YS, Samuel M, Song C. Meta-analysis of early excision of burns. Burns. Mar 2006;32(2):145-50. [Medline].
Wolf SE. Nutrition and metabolism in burns: state of the science, 2007. J Burn Care Res. Jul-Aug 2007;28(4):572-6. [Medline].
Albrecht MC, Griffith ME, Murray CK, Chung KK, Horvath EE, Ward JA, et al. Impact of Acinetobacter infection on the mortality of burn patients. J Am Coll Surg. Oct 2006;203(4):546-50. [Medline].
Church D, Elsayed S, Reid O, Winston B, Lindsay R. Burn wound infections. Clin Microbiol Rev. Apr 2006;19(2):403-34. [Medline].
Esselman PC. Burn rehabilitation: an overview. Arch Phys Med Rehabil. Dec 2007;88(12 Suppl 2):S3-6. [Medline].
Greenhalgh DG, Saffle JR, Holmes JH 4th, Gamelli RL, Palmieri TL, Horton JW, et al. American Burn Association consensus conference to define sepsis and infection in burns. J Burn Care Res. Nov-Dec 2007;28(6):776-90. [Medline].
Mayhall CG. The epidemiology of burn wound infections: then and now. Clin Infect Dis. Aug 15 2003;37(4):543-50. [Medline].
Regules JA, Carlson MD, Wolf SE, Murray CK. Analysis of anaerobic blood cultures in burned patients. Burns. Aug 2007;33(5):561-4. [Medline].
Regules JA, Glasser JS, Wolf SE, Hospenthal DR, Murray CK. Endocarditis in burn patients: Clinical and diagnostic considerations. Burns. Oct 26 2007;[Medline].
Schofield CM, Murray CK, Horvath EE, Cancio LC, Kim SH, Wolf SE, et al. Correlation of culture with histopathology in fungal burn wound colonization and infection. Burns. May 2007;33(3):341-6. [Medline].
Shankar R, Melstrom KA Jr, Gamelli RL. Inflammation and sepsis: past, present, and the future. J Burn Care Res. Jul-Aug 2007;28(4):566-71. [Medline].
Print
