The microbiology of necrotizing soft tissue infections
Section snippets
Materials and methods
The data reported herein are from a single institution, a 100-bed level I trauma center serving a state and surrounding region with population exceeding 5 million people and possessing a multipatient hyperbaric chamber capable of treating 21 patients simultaneously. Between March 1985 and June 1993, 198 patients with NSTI were admitted and treated. Diagnosis was confirmed by either histologic examination or a combination of clinical, microbiologic, and gross anatomic findings. All patients had
Results
Among the 198 patients studied, mortality was 25.3%, the average age was 51.5 years, male patients accounted for 57.3% of the total, and 56.4% of patients were diabetic. The mean extent of infection was 8.4% (±0.4%) of body surface area, and the most common sites of infection were perineal sources (Fournier’s gangrene, 36% of cases), podiatric sources (15.2%), and traumatic wounds (14.7%). Table I and Table IIlist the preexisting medical conditions and sites of origins among the study patients.
Comments
This retrospective analysis of 198 cases of NSTI establishes that such infections are capable of harboring a wide variety of microbial pathogens. Most infections are polymicrobial (average 4.4 microbes per case), but single-pathogen infections are not uncommon. Beta-hemolytic streptococci are the most frequent solitary pathogens (15 of 28 cases). The most common bacterial species overall include Bacteroides/Prevotella (116 isolates), streptococci (106 isolates), and gram-negative
Conclusions
Necrotizing soft tissue infections are frequently polymicrobial and initial antibiotic coverage with a broad-spectrum regimen is warranted. The initial regimen should include agents effective against aerobic gram-positive cocci, gram-negative rods, and a variety of anaerobes. The most common organisms not covered by initial therapy were enterococci. All wounds should be cultured at initial debridement, as changes in antibiotic coverage are frequent once isolates are recovered.
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