Annals of Burns and Fire Disasters - vol. XII - n° 4 - December 1999

SUMMARY. Objective: The aim of this study was to determine the aetiological factors, causative micro-organisms, mortality rate, and antimicrobial therapy in cases of invasive burn wound infection.
Methods: This is a retrospective study of 67 patients who presented invasive burn wound infection, representing 8.98% of the total number of burn patients admitted to three military hospitals in the south of Jordan from June 1990 to May 1998. Results: Children and the elderly were found to be the most commonly burned patients who developed invasive burn wound infection. Third-degree burns were found in 38.7% of the patients with burn wound infection. The most commonly isolated micro-organisms (50.8%) were fungi. Amputation was performed during treatment in 26.9% of the patients with invasive burns and only 29 patients out of the entire group survived. Conclusion: The factors found to be mainly implicated in invasive burn wound infection were burn extent and depth, and patient age. Antifungal therapy should be considered in every patient suffering from invasive burn wound infection.

Burn wound infection is classified as cellulitis, invasive infection, and hum wound impetigo. Burn wound cellulitis of bacterial origin is characterized by localized pain, tenderness, oedema, erythema, and hotness, associated with unburned and undamaged skin at the margin of burns and skin graft donor site. If untreated, the lesion expands with variable rapidity with or without a lymphangitis component. Group AB-haernolytic streptococci are the commonest offenders.
Impetigo is another form of burn wound infection that imay occur after a burn wound has healed or been grafted. This condition is characterized by loss of epithelium (initially focal but sometimes becoming generalized) from a previously grafted or healed burn wound or skin graft donor site. The commonest cause is Staphylococcus aureus.
The commonest local sign of invasive burn wound infection is the appearance of focal, multifocal, or generalized dark brown, black, or violaceous discoloration of the wound,' including conversion of an area of partialthickness injury to full-thickness necrosis or necrosis of previously viable tissue in an unexcised wound bed. This conversion becomes severe when infected by a phycomyeete. Other signs of invasive burn wound infection are given elsewhere.
The fungal action of the burn wound is characterized by unexpectedly rapid sloughing of the eschar due to fat liquefaction and rapid centrifugal spreading of subcutaneous oedema with central ischaemic necrosis. Exophthalmos may be the first sign of mucomycosis in mid-face burns, and its appearance should prompt biopsy of retrobulbar fat. Pseudomonas invasive burn wound infection is characterized by green pigment visible in subcutaneous fat, which is erythematous and later becomes a black, necrotic, nodular lesion (ecthyma gangrenosum).
Vesicular lesions and crusted serrated margins of partial-thickness facial burns are characteristic of burn wound infection of viral origin.

A retrospective study was carried out on 746 burn patients (289 female and 457 male) admitted to three military hospitals in southern Jordan from June 1990 to May 1998. The age range was from under 5 yr to 86 yr (Table 1). Aetiology and degree of burn are shown in Tables II and III.

All the patients received immediate care and resuscitation therapy with the application of normal saline to the affected areas, including chemical burns. Patients suffering from smoke inhalation received humidified oxygen by mask and pulmonary physiotherapy. The majority of the patients received a tetanus toxoid injection. The burns were dressed with silver sulphadiazine and 0.5% silver nitrate, followed by Ringer's lactate intravenous fluid. Infected burn wound patients were treated with broad-spectrum intravenous antibiotics before the laboratory results of the wound biopsy and the septic work-up, followed by appropriate treatment. Our laboratory lacks the technology for the isolation of viral or yeast species.

This study indicates that 8.98% of the burn patients examined had invasive burn wound infection. Fifty-three point nine per cent had second-degree burns, 13.8% had third-degree burns, and the remainder had first-degree burns. Table III shows that 61.19% of invasive burn wound infection patients had third-degree burns only, and only 38.80% presented second-degree burns.
Table IV presents patient age in relation to invasive burn wound infection.

The microbiological analysis of these patients with invasive burn wound infection showed that fungal infection was the commonest culprit, being responsible for 50.74% of the infections (Table V). The average time for microbial colonization of the burn wound was longest in fungi (27 days) (Table VI).
The various types of bacteria isolated from burn wound culture and biopsies of total invasive burn wound infection are shown in Table V. The picture clearly indicates that Pseudomonas was the commonest bacterial cause of invasive burn wound invasion, accounting for 42.6% of cases, while Escherichia coli caused only 11.3% of cases.

In this study the commonest causes of the burns were found to be scalding and dry heat (Table II). The incidence of invasive burn wound sepsis was proportional to the extent of the burn and was influenced by the depth of the burn and the age of the patient (Tables I, III). Invasive burn wound infection was observed only rarely in partialthickness injuries, occurring with greatest frequency in children and elderly patients and with lesser frequency in the elderly (Table IV). This shows a good correlation with results published in the literature.
The flora colonizing the burn wound influences the risk and the degree of infection. The gram-positive nature of the microbial population does not alter immediately after the burn, but with the passing of time gram-negative organisms colonize the eschar. By the end of the first week post-burn they become the predominant inhabitants of the burn wound.
Prior to the discovery of antibiotics, alpha- and betahaemolytic streptococci were the most frequent cause of life-threatening burn wounds and systemic infection. Penicillin therapy has however substantially eliminated this form of mortality. The use of penicillin led to the emergence of Staphylococcus aureus as the commonest gram-positive early colonizer of burn wounds." As Staphylococcus can be seeded into the circulation from an undrained abscess, early diagnosis and prompt drainage can minimize or prevent haernatogenous dissemination of staphylococcal infections.' The subsequent development and use of broad-spectrum antibiotics effective against Staphylococcus led to the emergence of gram-negative organisms, particularly Pseudomonas aeruginosa, as the predominant organism causing invasive burn wound infections in burn patients." The present investigation confirms that Klebsiella is the most resistant of all the gram-negative and gram-positive organisms studied, in accordance with the results published in the literature.
Table V shows that gram-negative organisms had much greater'invasive potential than gram-positive organisms. This is consistent with other findings."
The use of natural herbal MEBO ointment effectively reduced the incidence of burn wound sepsis as a cause of death, and similar reductions were achieved with mafenide acetate, 0.5% silver nitrate, and silver sulphadiazine cream. The present investigation suggests that fungi (Candida, Aspergillus, Fusarium) are the commonest cause of burn wound infection (Table V), and that it takes 27 days to colonize the burn wound (Table VI), compared with the above-reported bacterial infection.

Late burn wound excision and the peri-operative use of antibiotics to reduce the hazards of bacteraemia and bacterial dissemination are proposed here as possible reasons for this fungal burn wound infection. This finding is strongly supported by the work of Pruitt and McManus." The wound culture revealed that approximately 18% of the samples yielded negative laboratory results (Table V).
A high incidence of invasive burn wound infection is quite common in third-world countries, related to the late presentation (1-3 weeks) of burn patients. This delay can be attributed to the patients' poor level of education as well as to their firm belief in traditional medicines, e.g. topical application of tealeaves, henna (dried and powdered leaves of Lawsonia inermis lythtacaea), castor oil, yolk of egg, cauterization of the head, etc.).

RESUME. L'Auteur, dans cette étude, a déterminé les facteurs étiologiques, les micro-organismes responsables, le taux de mortalité et la thérapie antimicrobienne dans des cas d'infection invasive des brûlures. Il a effectué une étude rétrospective sur 67 patients atteints d'infection invasive des brûlures, qui constituaient 8,98% de tous les patients admis à trois hôspitaux militaires dans le sud du Jourdain dans la période juin 1990-mai 1998. Il a trouvé que les enfants et les personnes âgées étaient les patients les plus fréquemment atteints d'une infection invasive des brûlures et que les brûlures de troisième degré étaient présentes dans 38,7% des patients. Les micro-organismes les plus fréquemment isolés étaient les mycoses. Il a été nécessaire d'effectuer l'amputation dans 26,9% des patients atteints d'infection invasive des brûlures, dont seulement 29 ont survécu. Cette étude a démontré que les facteurs les plus importants dans l'infection invasive des brûlures étaient l'étendue et la profondité des brûlures, et l'âge du patient. Il faut considérer la thérapie antifongueuse dans tous les patients atteints d'infection invasive des brûlures.

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