Predictors of Monomicrobial Necrotizing Soft Tissue Infections

Necrotising fasciitis of the upper limb: a review of the literature

Necrotising fasciitis is an uncommon life-threatening surgical emergency. While most commonly seen in the lower limb it can also affect the upper limb. This article reviews and summarises the current literature on necrotising fasciitis in the upper limb, covering common predisposing factors, clinical presentations, scoring systems, common organism types and the timing of surgical treatment. The key to managing this condition continues to be early clinical diagnosis and aggressive surgical debridement to attempt to reduce the morbidity and mortality of this condition.

Necrotising soft-tissue infections

The incidence of necrotising soft-tissue infections has increased during recent decades such that most physicians might see at least one case of these potentially life-threatening infections in their career. Despite advances in care, necrotising soft-tissue infections are still associated with high morbidity and mortality, underlining a need for continued education of the medical community. In particular, failure to suspect necrotising soft-tissue infections, fuelled by poor awareness of the disease, promotes delays to first surgical debridement, amplifying disease severity and adverse outcomes. This Review will focus on practical approaches to management of necrotising soft-tissue infections including prompt recognition, initiation of specific management, exploratory surgery, and aftercare. Increased alertness and awareness for these infections should improve time to diagnosis and early referral to specialised centres, with improvement in the prognosis of necrotising soft-tissue infections.

Regional Variations in Microbiology and Outcomes of Necrotizing Soft Tissue Infections: A Systematic Review and Meta-Analysis

Background: Frequency, microbiology, and outcomes of necrotizing soft tissue infections (NSTIs) could vary across the United States because of differences in locoregional and environmental factors. We synthesized the literature from across the regions of the United States on NSTIs in a systematic review/meta-analysis. Methods: PubMed, ProQuest, Scopus, and Web of Science databases were systematically searched and screened. DerSimonian-Laird random-effects meta-analyses were performed using 'meta' package in R to determine pooled prevalences. Meta-regression analyses examined moderator effects of risk factors. Results: Twenty-seven studies (2,242 total patients) were included. Pooled prevalences of polymicrobial and monomicrobial infections were 52.2% and 39.9%, respectively. The prevalence of monomicrobial NSTIs increased over the last two decades (p = 0.018), whereas polymicrobial infections declined (p = 0.003). Meta-regression analysis showed that most polymicrobial NSTIs were Fournier gangrene (p < 0.001), whereas monomicrobial NSTIs mostly affected extremities (p < 0.001). Staphylococcus aureus was the most common organism isolated (predominantly in the South), followed by Bacteroides spp. (predominately in the East) and Streptococcus pyogenes. Methicillin-resistant Staphylococcus aureus (MRSA) accounted for 11.9% of NSTIs, mainly in the South. The overall mortality rate was 17.8% and declined over last two decades (p < 0.001), with the lowest rate reported in the last decade at 13% without any regional differences. Conclusions: Advancement in the management of NSTIs may have contributed to the observed decline in NSTI-related mortality in the United States. However, the proportion of monomicrobial NSTIs seems to be increasing, possibly because of increased comorbidities affecting extremities. Causative organisms varied by region. Multi-center observational studies are warranted to confirm our observations.

Antibiotics in Necrotizing Soft Tissue Infections

Necrotizing soft tissue infections (NSTIs) are rare life-threatening bacterial infections characterized by an extensive necrosis of skin and subcutaneous tissues. Initial urgent management of NSTIs relies on broad-spectrum antibiotic therapy, rapid surgical debridement of all infected tissues and, when present, treatment of associated organ failures in the intensive care unit. Antibiotic therapy for NSTI patients faces several challenges and should (1) carry broad-spectrum activity against gram-positive and gram-negative pathogens because of frequent polymicrobial infections, considering extended coverage for multidrug resistance in selected cases. In practice, a broad-spectrum beta-lactam antibiotic (e.g., piperacillin-tazobactam) is the mainstay of empirical therapy; (2) decrease toxin production, typically using a clindamycin combination, mainly in proven or suspected group A streptococcus infections; and (3) achieve the best possible tissue diffusion with regards to impaired regional perfusion, tissue necrosis, and pharmacokinetic and pharmacodynamic alterations. The best duration of antibiotic treatment has not been well established and is generally comprised between 7 and 15 days. This article reviews the currently available knowledge regarding antibiotic use in NSTIs.

Global patterns of necrotizing soft tissue infections: A systematic review and meta-analysis

BACKGROUND

Frequency, microbiology, and outcomes of necrotizing soft tissue infections vary based on locoregional and environmental factors; however, there has been no global survey of these patterns. We performed a systematic review/meta-analysis on published reports of necrotizing soft tissue infections from across the globe.

METHODS

Peer-reviewed empirical studies examining rates of polymicrobial and monomicrobial necrotizing soft tissue infections with microbial isolation and overall mortality rate were extracted along with geographic location using PubMed, Scopus, ProQuest, and Web of Science. Random-effects meta-analyses and sensitivity analyses were performed, adjusting for publication bias. Meta-regression analyses examined moderator effects of risk factors.

RESULTS

One hundred and five studies (8,718 total patients) were included. Pooled prevalence of polymicrobial and monomicrobial infections were 53% and 37.9%, respectively. Truncal necrotizing soft tissue infections were commonly polymicrobial (P < .001), whereas monomicrobial infections prevailed in extremities (P = .008). Global prevalence of monomicrobial necrotizing soft tissue infections was observed to increase by 1.1% annually (P = .003). Staphylococcus aureus was the most common organism globally and in North America, Asia, the Middle East, and Africa, followed by Streptococcus pyogenes and Escherichia coli. Methicillin-resistant S. aureus accounted for 16% of necrotizing soft tissue infections globally. Overall mortality was 23.1%, observed to decline globally over the last decade (P = .020). No regional differences were noted for mortality.

CONCLUSION

Although polymicrobial infections remain predominant worldwide, the incidence of monomicrobial infections is increasing. The observed decline in necrotizing soft tissue infection-related mortality is encouraging and may reflect advances in management, despite major variations in available healthcare resources globally.

Obesity Is Not an Independent Predictor of Necrotizing Soft Tissue Infection Outcomes

Background: Necrotizing soft tissue infections (NSTIs) are a group of rapidly progressive infections of the skin and its underlying tissue. These infections result in substantial morbidity and mortality. The focus of this study was to determine if obesity is associated with a worsened clinical outcome or prolonged hospital course for patients with NSTIs. Patients and Methods: We conducted a retrospective chart review of patients with NSTI presenting to a single tertiary hospital. Fat content, measured with body mass index (BMI) and abdominal fat thicknesses, including subcutaneous and visceral fat, were compared against primary and secondary outcomes of NSTIs. Results: We found that women had a higher mortality rate compared with men (27% vs. 15% mortality). Women also had an increased subcutaneous abdominal fat thickness (55.7 vs. 36.9 mm, p = 0.028). However, no measurements of fat, BMI, subcutaneous fat, or visceral fat differed between survivors and mortalities of NSTIs. In fact, with the exception of a higher BMI in those who developed acute kidney injury (AKI, p = 0.034), we found no correlation between increases in fat measurement and secondary outcome, including propensity to develop sepsis during hospitalization, length of hospital stay, length of intensive care stay, or antibiotic usage. Multivariable logistic regression analysis was conducted, and we found no statistically significant differences in primary or secondary outcomes. Conclusion: Women appear to have a higher mortality in NSTI, although the reasons for this are unclear. Obesity, as measured by BMI, subcutaneous, and visceral fat thicknesses, does not appear to be an independent risk factor.

The roles of early surgery and comorbid conditions on outcomes of severe necrotizing soft-tissue infections

PURPOSE

Severe necrotizing soft-tissue infections (NSTIs) require immediate early surgical treatment to avoid adverse outcomes. This study aims to determine the impact of early surgery and comorbid conditions on the outcomes of NSTIs.

METHODS

A retrospective cohort study was performed on all subjects presenting with NSTI at an academic medical center between 2005 and 2016. Patients were identified based on ICD codes. Those under the age of 18 or with intraoperative findings not consistent with NSTI diagnosis were excluded.

RESULTS

There were 115 patients with a confirmed diagnosis of NSTI with a mean age of 55 ± 18 years; 41% were females and 55% were diabetics. Thirty percent of patients underwent early surgery (< 6 h). There were no significant differences between groups in baseline characteristics. The late group (≥ 6 h) had prolonged hospital stay (38 vs. 23 days, p < 0.008) in comparison to the early group (< 6 h). With every 1 h delay in time to surgery, there is a 0.268 day increase in length of stay, adjusted for these other variables: alcohol abuse, number of debridements, peripheral vascular disease, previous infection and clinical necrosis. Mortality was 16.5%. Multivariable analysis revealed that alcohol abuse, peripheral vascular disease, diabetes, obesity, hypothyroidism, and presence of COPD were associated with an increase in mortality.

CONCLUSIONS

Early surgical intervention in patients with severe necrotizing soft-tissue infections reduces length of hospital stay. Presence of comorbid conditions such as alcohol abuse, peripheral vascular disease, diabetes, obesity and hypothyroidism were associated with increased mortality.

Fungal Infections Increase the Mortality Rate Three-Fold in Necrotizing Soft-Tissue Infections

BACKGROUND

Necrotizing soft-tissue infections (NSTIs) result in significant morbidity and mortality rates, with as many as 76% of patients dying during their index admission. Published data suggest NSTIs rarely involve fungal infections in immunocompetent patients. However, because of the recent recognition of fungal infections in our population, we hypothesized that such infections frequently complicate NSTIs and are associated with higher morbidity and mortality rates.

METHODS

A prospectively maintained Acute and Critical Care Surgery (ACCS) database spanning 2008-2015 and including more than 7,000 patients was queried for patients with NSTIs. Microbiologic data, demographics, and clinical outcomes were abstracted. Risk factors and outcomes associated with NSTI with positive intra-operative fungal cultures were determined. Frequencies were compared by χ² and continuous variables by the Student t-test using SPSS. Because the study included only archived data, no patient permission was needed.

RESULTS

A total of 230 patients were found to have NSTIs; 197 had intra-operative cultures, and 21 (10.7%) of these were positive for fungi. Fungal infection was more common in women, patients with higher body mass index (BMI), and patients who had had prior abdominal procedures. There were no significant differences in demographics, co-morbidities, or site of infection. The majority of patients (85.7%) had mixed bacterial and fungal infections; in the remaining patients, fungi were the only species isolated. Most fungal cultures were collected within 48 h of hospital admission, suggesting that the infections were not hospital acquired. Patients with positive fungal cultures required two more surgical interventions and had a three-fold greater mortality rate than patients without fungal infections.

CONCLUSIONS

This is the largest series to date describing the impact of fungal infection in NSTIs. Our data demonstrate a three-fold increase in the mortality rate and the need for two additional operations. Consideration should be given to starting patients on empiric anti-fungal therapy in certain circumstances.

The mythos of laudable pus along with an explanation for its origin

The presence of pus is one of the most easily recognizable signs of an infection. However, for several centuries suppuration, known as ‘laudable pus,’ was believed to be a sign of a healthy, healing wound. This historical misconception can be explained by the difference in the presentation of a necrotizing soft tissue infection versus other more common skin and soft tissue infections. Chronic wound infections, due to pyogenic bacteria, typically produce large amounts of thick, whitish-yellow pus. On the other hand, necrotizing soft tissue infections, despite their severe mortality and morbidity, are devoid of pus in the traditional sense. What the ancient medical observers recognized was the fact that pus is not characteristic of this subset of incredibly severe infections. This is an important distinction to remember when evaluating an infection, even today.