The microbiology of necrotizing soft tissue infections

OBJECTIVE: A large number of necrotizing soft tissue infections (NSTI) treated at a single institution over an 8-year period were analyzed with respect to microbial pathogens recovered, treatment administered, and outcome. Based on this analysis, optimal empiric antibiotic coverage is proposed. METHODS: A retrospective chart review of all patients with documented NSTI was conducted. Microbiologic variables were tested for impact on outcome using Fisher's exact test and multivariate analysis by logistic regression. RESULTS: Review of the charts of 198 patients with documented NSTI revealed 182 patients with sufficient microbiologic information for analysis. These 182 patients grew an average of 4.4 microbes from original wound cultures, although a single pathogen was responsible in 28 patients. Eighty-five patients had combined aerobic and anaerobic growth, the most common organisms being, in order, Bacteroides species, aerobic streptococci, staphylococci, enterococci, Escherichia coli, and other gram-negative rods. Clostridial growth was common but did not affect mortality unless associated with pure clostridial myonecrosis. Mortality was affected by the presence of bacteremia, delayed or inadequate surgery, and degree of organ system dysfunction on admission. CONCLUSIONS: NSTI 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.     

Hyperbaric oxygen therapy in necrotizing soft tissue infections

BackgroundSurgical debridement and antibiotics are the mainstays of therapy for patients with necrotizing soft tissue infections (NSTIs), but hyperbaric oxygen therapy (HBO) is often used as an adjunctive measure. Despite this, the efficacy of HBO remains unclear. We hypothesized that HBO would have no effect on mortality or amputation rates.MethodsWe performed a retrospective analysis of our institutional experience from 2005 to 2009. Inclusion criteria were age > 18 y and discharge diagnosis of NSTI. We abstracted baseline demographics, physiology, laboratory values, and operative course from the medical record. The primary endpoint was in-hospital mortality; the secondary endpoint was extremity amputation rate. We compared baseline variables using Mann-Whitney, chi-square, and Fisher's exact test, as appropriate. Significance was set at P < 0.05.ResultsWe identified 80 cases over the study period. The cohort was 54% male (n = 43) and 53% white (n = 43), and had a mean age of 55 ± 16 y. There were no significant differences in demographics, physiology, or comorbidities between groups. In-hospital mortality was not different between groups (16% in the HBO group versus 19% in the non-HBO group; P = 0.77). In patients with extremity NSTI, the amputation rate did not differ significantly between patients who did not receive HBO and those who did (17% versus 25%; P = 0.46).ConclusionsHyperbaric oxygen therapy does not appear to decrease in-hospital mortality or amputation rate after in patients with NSTI. There may be a role for HBO in treatment of NSTI; nevertheless, consideration of HBO should never delay operative therapy. Further evidence of efficacy is necessary before HBO can be considered the standard of care in NSTI.     

The use of drotrecogin alpha for necrotizing soft tissue infections

The use of Drotrecogin alfa (DAA) (Xigris) in select patients with sepsis has had demonstrable improvement in survival, though its benefit in necrotizing soft tissue infections (NSTI) is unclear. A retrospective review of NSTI patients receiving DAA at our institution from 2006 to 2009 was performed. Our previously derived mortality prediction model, based on classification and regression tree analysis, was applied to patients and the predicted mortality was compared with the actual mortality rate. Ten patients with severe NSTI received DAA. The median admission values were: white blood cell count of 27,000/mm3, serum lactate of 4.0 mmol/L, and serum sodium of 128 mEq/L. Four (40%) patients had systemic complications, five (50%) patients required amputation, and one died (10%). Median time to DAA administration was 12 hours after debridement. There were no bleeding complications attributed to DAA use. Mortality in this series of severe NSTI was only 10 per cent, which compares favorably with the predicted mortality of 18 per cent based on classification and regression tree analysis (P = 0.2). A prospective, randomized study is warranted to determine if the use of DAA should be part of the standard therapy for NSTI patients with a predicted high mortality.     

Strategies of management of necrotizing soft tissue infections

Necrotizing soft tissue infections represent a group of rapidly progressive diseases requiring early and repeated debridement, associated with broad spectrum antibiotics. Delay in surgery or inadequate therapy are the main risk factors for death. Most patients need aggressive critical care management and intensive nutritional support. The management of these patients by experimented senior surgeons is mandatory. A plastic surgeon can help debridement in order to preserve possibilities of later myocutaneous or rotational skin flaps. Intravenous immunoglobulins are an efficacious adjunctive therapy for severe group A streptococcal infection.     

Outcome of necrotizing skin and soft tissue infections

ABSTRACT Background: Management of necrotizing skin and soft tissue infections (nSSTI) remains difficult, and the mortality rate has been high. We hypothesized that management of nSSTI by an emergency general surgery (EGS) service would improve outcomes. Methods: Retrospective review of EGS patients with idiopathic nSSTI and comparison with historical controls. Demographic, co-morbidity, laboratory, and surgical data were collected. Non-parametric statistical analysis was used to evaluate differences between survivors and non-survivors. Logistic regression analysis was performed to identify risk factors for the primary outcome measure of death. Results: Fifty-two patients met the inclusion criteria, with five deaths (9.6%). The median time to the operating room (OR) was 8.6 h. The Acute Physiology and Chronic Health Evaluation (APACHE) II score, serum lactic acid concentration, and intensive care unit length of stay were significantly different for non-survivors. The APACHE II score was an independent predictor of death when controlling for age and time to OR. Conclusions: An EGS service was associated with shorter time to OR, which may improve the outcome. Physiologic derangement, as estimated by the APACHE II score, is predictive of death from nSSTI.     

Predictors of mortality and limb loss in necrotizing soft tissue infections

HYPOTHESIS: Necrotizing soft tissue infections are associated with a high mortality rate. We hypothesize that specific predictors of limb loss and mortality in patients with necrotizing soft tissue infection can be identified on hospital admission. DESIGN: A retrospective cohort study. SETTING: A tertiary care center. PATIENTS: Patients with a diagnosis of necrotizing soft tissue infection during a 5-year period (1996-2001) were included. Patients were identified with International Classification of Diseases, Ninth Revision hospital discharge diagnosis codes, and diagnosis was confirmed by medical record review. INTERVENTIONS: Standard current treatment including early and scheduled repeated debridement, broad-spectrum antibiotics, and physiologic and nutritional support was given to all patients. MAIN OUTCOME MEASURES: Limb loss and mortality. RESULTS: One hundred sixty-six patients were identified and included in the study. The overall mortality rate was 16.9%, and limb loss occurred in 26% of patients with extremity involvement. Independent predictors of mortality included white blood cell count greater than 30 000 x 10(3)/microL, creatinine level greater than 2 mg/dL (176.8 micromol/L), and heart disease at hospital admission. Independent predictors of limb loss included heart disease and shock (systolic blood pressure <90 mm Hg) at hospital admission. Clostridial infection was an independent predictor for both limb loss (odds ratio, 3.9 [95% confidence interval, 1.1-12.8]) and mortality (odds ratio, 4.1 [95% confidence interval, 1.3-12.3]) and was highly associated with intravenous drug use and a high rate of leukocytosis on hospital admission. The latter was found to be a good variable in estimating the probability of death. CONCLUSIONS: Clostridial infection is consistently associated with poor outcome. This together with the independent predictors mentioned earlier should aid in identifying patients on hospital admission who may benefit from more aggressive and novel therapeutic approaches.     

Severe cervical skin and soft tissue infections and necrotizing fasciitis

Cervical severe skin and soft tissue infections and necrotizing fasciitis originate from dental or pharyngeal infections. When compared to other forms of skin and soft tissue infections, they are recognized late, usually after one week of evolution often in a patient receiving antibiotic treatments. Extensions toward adjacent anatomical structures including mediastinum lead to a life-threatening prognosis. The cutaneous appearance of these severe infections is usually inflammatory cervical signs combined to facial oedema. These moderate clinical signs require immediate surgery after CT scan imaging.     

Massive soft tissue infections: necrotizing fasciitis and purpura fulminans

Necrotizing fasciitis and purpura fulminans are two destructive infections that involve both skin and soft tissue. Necrotizing fasciitis is characterized by widespread necrosis of subcutaneous tissue and the fascia. Historically, group A beta-hemolytic streptococcus has been identified as a major cause of this infection. However, this monomicrobial infection is usually associated with some underlying cause, such as diabetes mellitus. During the last two decades, scientists have found that the pathogenesis of necrotizing fasciitis is polymicrobial. The diagnosis of necrotizing fasciitis must be made as soon as possible by examining the skin inflammatory changes. Magnetic resonance imaging is strongly recommended to detect the presence of air within the tissues. Percutaneous aspiration of the soft tissue infection followed by prompt Gram staining should be conducted with the "finger-test" and rapid-frozen section biopsy examination. Intravenous antibiotic therapy is one of the cornerstones of managing this life-threatening skin infection. Surgery is the primary treatment for necrotizing fasciitis, with early surgical fasciotomy and debridement. Following debridement, skin coverage by either Integra Dermal Regeneration Template or AlloDerm should be undertaken. Hyperbaric oxygen therapy complemented by intravenous polyspecific immunoglobulin are useful adjunctive therapies. Purpura fulminans is a rare syndrome of intravascular thrombosis and hemorrhagic infarction of the skin; it is rapidly progressive and accompanied by vascular collapse. There are three types of purpura fulminans: neonatal purpura fulminans, idiopathic or chronic purpura fulminans, and acute infectious purpura fulminans. Clinical presentation of purpura fulminans involves a premonitory illness followed by the rapid development of a septic syndrome with fever, shock, and disseminated intravascular coagulation. The diagnosis and treatment of these conditions is best accomplished in a regional burn center in which management of multiple organ failure can be conducted with aggressive debridement and fasciotomy of the necrotic skin. The newest revolutionary advancement in the treatment of neonatal purpura fulminans is the use of activated protein C.     

Treatment of necrotizing soft tissue infections. The need for a new approach

Necrotizing soft tissue infections are classified by the type of infecting organism, the presenting clinical picture, and the treatment required. However, reliance on this schema is impractical since it often leads to an inordinate delay in appropriate surgical therapy with an unwarranted loss of a limb or life. Since 1958, 21 patients were treated at the UCLA Medical Center with necrotizing soft tissue infections. Unifocal ulcerations and nonspreading infections were excluded. Of the 21 patients, the initial classification of the infections included necrotizing fasciitis in 38 percent, clostridial gangrene in 38 percent, bacterial synergistic gangrene in 19 percent, and streptococcal hemolytic gangrene in 5 percent. Diabetes or evidence of immunosuppression was found in 71 percent of the patients. The course could be traced to either a perforated viscus in 43 percent or a traumatic injury in 43 percent. No single clinical sign, including tissue gas, was diagnostic for a specific type of necrotizing soft tissue infection. Culture revealed a polymicrobial flora in 76 percent. Overall mortality was 52 percent and the amputation rate was 36 percent. Mean time to appropriate surgical therapy was 1.9 days. Operations performed more than 24 hours after recognition of infection resulted in a 70 percent mortality versus a 36 percent mortality when operations were performed less than 24 hours after recognition. A lesser operation to conserve tissue resulted in a 71 percent mortality versus a 43 percent mortality with initial radical surgery which encompassed all devitalized tissue. Based on these data, we conclude that classification of necrotizing soft tissue infections should be simplified to clostridial and nonclostridial infections. Radical operative debridement, regardless of tissue loss, should be carried out immediately after fluid resuscitation, and antibiotic coverage must be broad spectrum from the time of onset due to the polymicrobial nature of these infections.     

Diagnosis and thereapy of necrotizing soft tissue infections of the perineum

Nine patients with necrotizing soft tissue infection of the perineum and adjacent areas developed following perirectal absecess, retroperitoneal infection, local trauma or apparently spontaneously. Skin changes and crepitus were often present but severe local pain was the only indication of infection in three patients. Repeated surgery or in one case, a necropsy, were required to uncover the extensive, dissecting, purulent and necrotizing subcutaneous process. Myonecrosis had occurred in three cases. Operation was often delayed for several days because of the difficulty in recognizing the presence of infection or because the urgency for treating an already apparent infection was not appreciated. The mortality was high (5/9 cases). The bacterial isolates were predominantly of a mixed aerobic-anaerobic nature. Needle aspiration of suspicious areas, even where classic signs of inflammation are lacking and Gram staining of exudate are valuable procedures for diagnosis and institution of appropriate presumptive antibiotic treatment. Thorough surgical exploration and debridement must be performed promptly to maximize chances for survival.     

The use of extracorporeal membrane oxygenation in severe necrotizing soft tissue infections complicated by septic shock

Necrotizing soft tissue infections remain a challenging clinical problem. Delays in diagnosis, incomplete débridement of necrotic tissues, and the hemodynamic instability and end-organ failure associated with overwhelming sepsis all contribute to significant mortality. Extracorporeal support is a well-established tool to support profound cardiopulmonary failure. To broaden the indications for use, we present two cases of young adults with necrotizing soft tissue infections who sustained sepsis-induced hemodynamic collapse and required extracorporeal support to facilitate adequate tissue débridement as a bridge to recovery.     

Trends in 393 necrotizing acute soft tissue infection patients 2000-2008

ObjectiveTo determine the outcomes effect of changing trends in patients with necrotizing acute soft tissue infections (NASTI) 2000–2008.MethodsA single institution retrospective chart review of all patients treated for NASTI.ResultsThere were 393 patients with mean age 50 years, diabetes 53%, % body surface area excised 3.5. Wounds were located on: extremity 57%, perineum 40%, trunk 26%. Wound cultures %: polymicrobial = 62, Staphylococci = 48, Streptococci = 31. Patients developing complications %: Pulmonary = 23, renal insufficiency/failure = 27. During the study period, overall mortality rate remained unchanged: 30/393 = 7.6% (5.5% for patients first admitted by burn/trauma/acute care surgery vs. 29% for all other services, p = 0.003). Significant annual increases were found in number of patients, p = 0.03, male sex, p = 0.000, transfer from outside hospital, p < 0.001, BMI p = 0.003, ventilator requirement >24 h, p = 0.0005, APACHE II p = 0.002, and number of patients developing any complication, p = 0.04. Statistically significant decreases annually were found in: days of antibiotic use, p = 0.008, number of operations required for excision, p = 0.02, development of non-wound infections, p = 0.002, and length of stay in days (LOS), p = 0.03.ConclusionsThis is the largest cohort of NASTI patients from a single institution to date, demonstrating significantly shorter LOS and decreased non-wound infection rates in the face of increasing BMI and APACHE II scores. The increasing number of patients and BMI suggests a causal relationship between NASTI and obesity. Initial care by surgeons experienced in caring for these patients provides mortality rates well below the national average.     

肝硬化合并皮肤软组织感染研究进展

肝硬化患者因其免疫力低下、下肢水肿等原因是皮肤软组织感染的高危人群,常见的皮肤软组织感染部位为下肢,常见的感染类型为蜂窝织炎。与一般人群不同,肝硬化患者合并皮肤软组织感染的病原体以革兰阴性杆菌为主。血清肌酐值和MELD评分为肝硬化患者合并皮肤软组织感染预后不良的预测因素。我国肝硬化患者合并皮肤软组织的病原学与临床特征尚需进一步明确,旨在为优化此类患者的优化管理提供一定的依据。     

Procalcitonin ratio as a predictor of successful surgical treatment of severe necrotizing soft tissue infections

Background

Necrotizing soft tissue infections often are characterized by fulminant presentation and lethal outcomes. Besides critical care support and antibiotic therapy, aggressive surgical treatment is important for the therapy of necrotizing fasciitis. The aim of this study was to develop a procalcitonin (PCT) ratio indicating successful surgical intervention.

Methods

The study group consisted of 38 patients treated with clinical signs of sepsis caused by a necrotizing soft tissue infection. All patients received radical surgical treatment, and serum levels of PCT and C-reactive protein were monitored postoperatively. The ratio of day 1 to day 2 was calculated and correlated with the successful elimination of the infectious source and clinical recovery.

Results

An eradication of the infectious focus was successfully performed in 84% of patients, averaging 1.9 operations (range 1 to 6) to achieve an elimination of the infectious source. The PCT ratio was significantly higher in the group of patients with successful surgical intervention (1.665 vs .9, P < .001). A ratio higher than the calculated cutoff of 1.14 indicated successful surgical treatment with a sensitivity of 83.3% and a specificity of 71.4%. The positive predictive value was 75.8%, and the negative predictive value was 80.0%.

Conclusions

The PCT ratio of postoperative day 1 to day 2 following major surgical procedures for necrotizing soft tissue infections represents a valuable clinical tool indicating successful surgical eradication of the infectious focus.     

Perineal soft tissue infections

Fournier's gangrene (FG) is an aggressive necrotizing soft tissue infection of the perineum. FG takes hold as a mixture of pathogenic organisms enter the host via injured gastrointestinal or genitourinary mucosa. After soft tissue insult, a synergistic, polymicrobial infection destroys tissue through an obliterative endarteritis. FG particularly affects older, obese men with type 2 diabetes mellitus, but can affect everyone. Special populations at risk include patients who have undergone gender reassignment surgery. Early, aggressive debridement and fluid resuscitation are mandatory. Careful decisions must be made regarding the fecal stream, antibiosis, topical coverings and the use of adjunctive therapy. While untreated FG is certainly fatal, with effective diagnosis and treatment survival rates approach 95%.     

Necrotizing soft tissue infections

Necrotizing soft tissue infections (NSTI) represent a spectrum of diseases characterized by extensive rapidly progressive necrosis that may involve the skin, subcutaneous tissues, fascia or muscle. Their progress is extremely fast, leading often to sepsis and septic shock that ends up in multiple organ failure with abrupt and high mortality. A variety of classification systems have been developed based on parameters such as anatomic location of the disease or microbiology. There are a number of factors that predispose to the spread of these soft tissue infections, such as delays in recognition, immune suppression, diabetes mellitus and advanced age. The use of broad‐spectrum antibiotics tends to mask the severity of the underlying infection, modulates the clinical presentation, and even delays hospital admission. The most important factor affecting outcome in NSTI is early diagnosis and aggressive radical surgical treatment. The medical records of 13 patients who had been treated for NSTI from 1996 to 2005 were reviewed, retrospectively. There were eight men (61.5%) and five (38.5%) women. Mean age was 56 years (range 27–73). Seven cases of infection involved the perineal region (54%), two the lower limb, one the upper limb and three the abdominal wall/trunk. The most common associated comorbidity was diabetes mellitus in five patients (38.5%). A single organism was identified in two (15%) and multiple organisms in 11 (85%) patients. Necrotizing aponeurositis Type I was the most common of the polymicrobial necrotizing infections. Overall survival was 85%, and the mean hospital stay for survivors was 35 days (range 17–92).     

Lower-extremity soft tissue infections with intra-abdominal sources

This article describes a series of 3 patients who presented with lower-extremity soft tissue infections. Each patient was treated with prompt debridement by an orthopedic surgeon (J.F.G.) and required at least 1 additional procedure by another surgeon.These infections vary from superficial cellulitis to rapidly advancing necrotizing fasciitis. At times, the source of these infections is clear. Other times, no obvious source of infection exists, in which case the abdomen must be considered as a possible source of infection. A high level of suspicion, complete history and physical examination, and appropriate ancillary studies are required to make an accurate and prompt diagnosis. Options for the treatment of the intra-abdominal source of infection depend on the etiology of the infection and anatomic location of the process. Psoas abscesses can often be decompressed by an interventional radiologist using computed tomography guidance. In the case of bowel involvement, such as suspected carcinoma or diverticulitis, a general surgeon is necessary. When the appropriate diagnosis is made, soft tissue infections of the thigh often respond to appropriate surgical debridement and antibiotic therapy. It is important to remember the whole patient when evaluating soft tissue infections, especially in the thigh. A low threshold for imaging of the abdomen and pelvis is important, especially when the physical examination or medical history reveals the abdomen as a possible source of infection.     

Skin and soft tissue infections

Infection can involve all layers of soft tissue. The severity of infection can range from a simple cutaneous infection to widespread necrosis of the skin, muscle, and fascia. While infections of soft tissue are common, and can usually be managed using conservative therapy or local surgery, clinicians should be aware of less commonly seen invasive infections that need immediate radical surgical débridement to treat the source adequately, contributing to improved survival.