Biomarkers of necrotising soft tissue infections: aspects of the innate immune response and effects of hyperbaric oxygenation-the protocol of the prospective cohort BIONEC study

A prospective study on skin and soft tissue infections: a fact-finding mission from a tertiary centre in north India

OBJECTIVE

Despite the high prevalence and poor outcome of skin and soft tissue infections (SSTIs), very few studies from India have dealt with the subject. We planned a prospective study of inpatients with SSTIs to study the aetiology, clinical presentation (severity) and outcome of patients with SSTIs in our facility.

METHOD

Patients with SSTIs involving >5% body surface area (BSA) and/or systemic signs were admitted to the surgery department of a teaching tertiary level hospital in Delhi, India, and were clinically classified into cellulitis, necrotising soft tissue infections (NSTIs), pyomyositis, and abscess. Demographic and clinical variables such as: age; sex; occupation; history of trauma/insect or animal bites; duration of illness; presenting symptoms and signs; comorbid conditions; predisposing factors such as lymphoedema or venous disease; hospital course; treatment instituted; complications; hospital outcome; presence of crepitus, bullae, gangrene, muscle necrosis and compartment syndrome were recorded. The chief outcome parameters were death and length of hospital stay; others, such as abscess drainage, the need for plastic surgical procedures and amputations were also noted.

RESULTS

Out of 250 patients enrolled in the study, 145 (58%) had NSTIs, 64 (26%) had abscesses, 15 (6%) had cellulitis and 26 (10%) had pyomyositis. Mortality was observed with NSTIs (27/145, 19%) and with pyomyositis (3/26, 11.5%). Factors affecting mortality by univariate analysis in the NSTI group were: abnormal pulse; hypotension; tachypnea; bullae; increased blood urea and serum creatinine; inotrope or ventilator support (all with p<0.001); local tenderness, gangrene, dialysis support and BSA (9.33±6.44 versus 5.12±3.62; p<0.05 for the last four). No factor was found to be significant on multivariate analysis. Variables associated with hospital stay >12 days were immunocompromise, pus discharge, ulceration or gangrene, and after interventions such as blood transfusion, drainage or skin grafting.

CONCLUSION

High prevalence of NSTI and pyomyositis with high mortality was observed in our SSTI patients, often in immunocompetent young individuals. Epidemiological studies focused on virulent strains of Staphylococcus aureus may be required to identify the cause, since Staphylococcal toxins have been implicated in other infections.

Associations between YKL-40 and markers of disease severity and death in patients with necrotizing soft-tissue infection

Background

Necrotizing soft-tissue infection (NSTI) is a severe and fast-progressing bacterial infection. Prognostic biomarkers may provide valuable information in treatment guidance and decision-making, but none have provided sufficient robustness to have a clinical impact. YKL-40 may reflect the ongoing pathological inflammatory processes more accurately than traditional biomarkers as it is secreted by the activated immune cells, but its prognostic yields in NSTI remains unknown. For this purpose, we investigated the association between plasma YKL-40 and 30-day mortality in patients with NSTI, and assessed its value as a marker of disease severity.

Methods

We determined plasma YKL-40 levels in patients with NSTI (n = 161) and age-sex matched controls (n = 65) upon admission and at day 1, 2 and 3.

Results

Baseline plasma YKL-40 was 1191 ng/mL in patients with NSTI compared with 40 ng/mL in controls (p < 0.001). YKL-40 was found to be significantly higher in patients with septic shock (1942 vs. 720 ng/mL, p < 0.001), and in patients receiving renal-replacement therapy (2382 vs. 1041 ng/mL, p < 0.001). YKL-40 correlated with Simplified Acute Physiology Score II (Rho 0.33, p < 0.001). Baseline YKL-40 above 1840 ng/mL was associated with increased risk of 30-day mortality in age-sex-comorbidity adjusted analysis (OR 3.77, 95% CI; 1.59–9.24, p = 0.003), but after further adjustment for Simplified Acute Physiology Score II no association was found between YKL-40 and early mortality.

Conclusion

High plasma YKL-40 to be associated with disease severity, renal-replacement therapy and risk of death in patients with NSTI. However, YKL-40 is not an independent predictor of 30-day mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06760-x.

Anti-biofilm Approach in Infective Endocarditis Exposes New Treatment Strategies for Improved Outcome

Infective endocarditis (IE) is a life-threatening infective disease with increasing incidence worldwide. From early on, in the antibiotic era, it was recognized that high-dose and long-term antibiotic therapy was correlated to improved outcome. In addition, for several of the common microbial IE etiologies, the use of combination antibiotic therapy further improves outcome. IE vegetations on affected heart valves from patients and experimental animal models resemble biofilm infections. Besides the recalcitrant nature of IE, the microorganisms often present in an aggregated form, and gradients of bacterial activity in the vegetations can be observed. Even after appropriate antibiotic therapy, such microbial formations can often be identified in surgically removed, infected heart valves. Therefore, persistent or recurrent cases of IE, after apparent initial infection control, can be related to biofilm formation in the heart valve vegetations. On this background, the present review will describe potentially novel non-antibiotic, antimicrobial approaches in IE, with special focus on anti-thrombotic strategies and hyperbaric oxygen therapy targeting the biofilm formation of the infected heart valves caused by Staphylococcus aureus. The format is translational from preclinical models to actual clinical treatment strategies.

Necrotizing Soft Tissue Infections

Necrotizing soft tissue infections occur after traumatic injuries, minor skin lesions, nonpenetrating injuries, natural childbirth, and in postsurgical and immunocompromised patients. Infections can be severe, rapidly progressive, and life threatening. Survivors often endure multiple surgeries and prolonged hospitalization and rehabilitation. Despite subtle nuances that may distinguish one entity from another, clinical approaches to diagnosis and treatment are highly similar. This review describes the clinical and laboratory features of necrotizing soft tissue infections and addresses recommended diagnostic and treatment modalities. It discusses the impact of delays in surgical debridement, antibiotic use, and resuscitation on mortality, and summarizes key pathogenic mechanisms.

Associations of Plasma Nitrite, L-Arginine and Asymmetric Dimethylarginine With Morbidity and Mortality in Patients With Necrotizing Soft Tissue Infections

Background:

The nitric oxide system could play an important role in the pathophysiology related to necrotizing soft tissue infection (NSTI). Accordingly, we investigated the association between plasma nitrite level at admission and the presence of septic shock in patients with NSTI. We also evaluated the association between nitrite, asymmetric dimethylarginine (ADMA), l-arginine, l-arginine/ADMA ratio, and outcome.

Methods:

We analyzed plasma from 141 NSTI patients taken upon hospital admission. The severity of NSTI was assessed by the presence of septic shock, Simplified Acute Physiology Score (SAPS) II, Sepsis-Related Organ Failure Assessment (SOFA) score, use of renal replacement therapy (RRT), amputation, and 28-day mortality.

Results:

No difference in nitrite levels was found between patients with and without septic shock (median 0.82 μmol/L [interquartile range (IQR) 0.41–1.21] vs. 0.87 μmol/L (0.62–1.24), P = 0.25). ADMA level was higher in patients in need of RRT (0.64 μmol/L (IQR 0.47–0.90) vs. (0.52 μmol/L (0.34–0.70), P = 0.028), and ADMA levels correlated positively with SAPS II (rho = 0.32, P = 0.0002) and SOFA scores (rho = 0.22, P = 0.01). In a logistic regression analysis, an l-arginine/ADMA ratio below 101.59 was independently associated with 28-day mortality, odds ratio 6.03 (95% confidence interval, 1.41–25.84), P = 0.016. None of the other analyses indicated differences in the NO system based on differences in disease severity.

Conclusions:

In patients with NSTI, we found no difference in baseline nitrite levels according to septic shock. High baseline ADMA level was associated with the use of RRT and patients with a low baseline l-arginine/ADMA ratio were at higher risk of dying within 28 days after hospital admission.

The Role of Streptococcal and Staphylococcal Exotoxins and Proteases in Human Necrotizing Soft Tissue Infections

Necrotizing soft tissue infections (NSTIs) are critical clinical conditions characterized by extensive necrosis of any layer of the soft tissue and systemic toxicity. Group A streptococci (GAS) and Staphylococcus aureus are two major pathogens associated with monomicrobial NSTIs. In the tissue environment, both Gram-positive bacteria secrete a variety of molecules, including pore-forming exotoxins, superantigens, and proteases with cytolytic and immunomodulatory functions. The present review summarizes the current knowledge about streptococcal and staphylococcal toxins in NSTIs with a special focus on their contribution to disease progression, tissue pathology, and immune evasion strategies.

Association between cytokine response, the LRINEC score and outcome in patients with necrotising soft tissue infection: a multicentre, prospective study

Early assessment of necrotising soft tissue infection (NSTI) is challenging. Analysis of inflammatory markers could provide important information about disease severity and guide decision making. For this purpose, we investigated the association between cytokine levels and the Laboratory Risk Indicator for Necrotising Fasciitis (LRINEC)-score, disease severity and mortality in NSTI patients. In 159 patients, plasma was analysed for IL-1β, IL-6, IL-10 and TNF-α upon admission. The severity of NSTI was assessed by SAPS, SOFA score, septic shock, microbial aetiology, renal replacement therapy and amputation. We found no significant difference in cytokine levels according to a LRINEC- score above or below 6 (IL-1β: 3.0 vs. 1.3; IL-6: 607 vs. 289; IL-10: 38.4 vs. 38.8; TNF-α: 15.1 vs. 7.8 pg/mL, P > 0.05). Patients with β-haemolytic streptococcal infection had higher level of particularly IL-6. There was no difference in mortality between patients with a LRINEC-score above or below 6. In the adjusted analysis assessing 30-day mortality, the association was strongest for IL-1β (OR 3.86 [95% CI, 1.43-10.40], P = 0.008) and IL-10 (4.80 [1.67-13.78], P = 0.004). In conclusion, we found no significant association between the LRINEC-score and cytokine levels on admission. IL-6 was consistently associated with disease severity, whereas IL-1β had the strongest association with 30-day mortality.

The Lectin Complement Pathway in Patients with Necrotizing Soft Tissue Infection

BACKGROUND

Mannose-binding lectin (MBL) and ficolins are pattern recognition molecules (PRMs) that play an important role during infection through activation of the lectin complement pathway. We assessed whether plasma PRM levels were associated with mortality in patients with necrotizing soft tissue infection (NSTI).

METHODS

We conducted a prospective, observational study over 25 months involving 135 NSTI patients with a maximum follow-up of 2.7 years. Blood samples were taken upon admission. Non-infected patients served as controls.

RESULTS

PRM levels were significantly lower compared with controls. A baseline Ficolin-2 level below the median was associated with mortality at the end of follow-up (p = 0.007). No significant association was found for MBL, Ficolin-1 and Ficolin-3. A Ficolin-2 level below the median had a negative predictive value of 0.94 for 28-day mortality, and a level below the optimal cut-off was independently associated with 28-day mortality when adjusted for age, sex and chronicity [hazard ratio 6.27 (95% confidence interval 2.28-17.21), p < 0.0001], also when Simplified Acute Physiology Score II was included in the analysis [hazard ratio 3.16 (95% confidence interval 1.03-9.73), p = 0.045].

CONCLUSIONS

All PRMs were significantly lower in patients with NSTI than in controls. Only baseline Ficolin-2 was associated with short- and long-term mortality. A high baseline Ficolin-2 level indicated a 94% chance of surviving the first 28 days after admission.

Pentraxin-3 as a marker of disease severity and risk of death in patients with necrotizing soft tissue infections: a nationwide, prospective, observational study

Background

New biomarkers are needed to assess the severity of necrotizing soft tissue infection (NSTI) at an early stage and to individualize treatment strategies. We assessed pentraxin-3 (PTX3) as a marker of disease severity and risk of death in patients with NSTI.

Methods

We conducted a prospective, observational study in the intensive care unit at Copenhagen University Hospital, where treatment of NSTI is centralized at a national level. We compared PTX3, procalcitonin and C-reactive protein in septic shock versus nonshock patients and in amputated versus nonamputated patients using the Mann-Whitney U test. The prognostic value of the markers for 180-day mortality was assessed using Cox regression analyses.

Results

Patients with NSTI (n = 135) were included over 25 months with up to 2.5-year follow-up; 71 % had septic shock, amputation was undertaken in 20 % and the 180-day mortality was 27 %. Baseline plasma PTX3 level was significantly higher in patients with septic shock (67.3 versus 24.6 ng/mL, p < 0.0001) and in patients who underwent amputation (118.6 versus 43.6 ng/mL, p = 0.019). No significant differences in baseline procalcitonin or C-reactive protein levels were found according to amputation (25.2 versus 7.0 μg/L, p = 0.060 and 202 versus 225 mg/L, p = 0.123), respectively. Baseline PTX3 level above the median was associated with death (p = 0.009, log-rank test) and the univariate Cox regression analysis revealed a significant association between PTX3 level upon admission and 180-day mortality (hazard ratio 2.60 (95 % confidence interval 1.28–5.29), p = 0.008). When adjusted for age, sex, chronic disease and Simplified Acute Physiology Score II, no significant association was found.

Conclusions

High PTX3 level is associated with septic shock, amputation and risk of death in patients with NSTI, but it is not an independent predictor of 180-day mortality in this patient group.

Trial registration

ClinicalTrials.gov Identifier: NCT02180906. Date of registration: June 29, 2014.