Epidemiology of invasive group A streptococcal infections in Norway 2010–2014: A retrospective cohort study

Clinical and microbiological characterization of invasive group a Streptococcus infection in children in Japan: A single-center experience

BACKGROUND

Invasive group A Streptococcus (iGAS) infections are rare but potentially fatal. Although the number of invasive group A Streptococcus (iGAS) infections decreased during the coronavirus disease (COVID-19) pandemic, it sharply increased worldwide following the pandemic due to the emergence of M1UK strains. In Japan, non-fluminant iGAS infections have not been included in the national survey notification system. Therefore, the clinical and microbiological characteristics of iGAS infection are unknown. In this study, we aimed to clarify the clinical and microbiological characteristics of pediatric iGAS infections.

METHODS

We conducted a case-series analysis of children aged 0-15 years with positive Streptococcus pyogenes cultures from otherwise sterile sites, diagnosed between July 2018 and June 2024. Clinical data were extracted from the electronic medical records. Samples of clinical isolates were sent to the Public Health Research Institute for further analysis.

RESULTS

We identified 11 patients (median age, 5 years [interquartile range 1-8.5 years]; 6 girls). The incidence rate of the iGAS infections was highest in 2024, with 3 cases in 6 months. Primary bacteremia without focal infection was the predominant diagnosis, followed by skin and soft tissue infections with bacteremia. Among the 11 iGAS infections, 9 isolates were available for additional microbiological tests. M12 and M1 strains were predominant (four cases each). Three of the four M1 isolates were M1UK strains.

CONCLUSIONS

In the present study, the increasing incidence of iGAS infection and clinical diagnoses are similar to those reported in other countries; however, M12 strains as well as M1 strains are predominant.

Perforated colon cancer complicated by necrotizing soft tissue infection: A case report and literature review

Necrotizing soft tissue infections (NSTIs) are rare but life-threatening complications of colorectal cancer, often overlooked during patient diagnosis and treatment. NSTIs progress rapidly, leading to significant tissue damage and elevated mortality rates. This report presents the case of a 71-year-old male who presented with abdominal pain and distention, later diagnosed with perforated colon cancer and NSTI of the left abdominal wall. Following admission, the patient developed septic shock and acute kidney injury. Emergency surgery was performed, including radical resection of the colon cancer, proximal colostomy, and extensive debridement of necrotic tissue. Postoperatively, Continuous Renal Replacement Therapy (CRRT) was used alongside standard treatments, contributing to a relatively rapid recovery. At the 30-month follow-up, no evidence of tumor recurrence was observed.

Streptococcal Toxic Shock Syndrome Caused by a Streptococcus pyogenes emm22 Genotype with a CsrS Mutation: a Case Report

A previously healthy 22-year-old woman was admitted to our hospital after an out-of-hospital cardiac arrest. Spontaneous circulation was restored prior to arrival at the hospital. However, the patient's vital signs remained unstable. Vasopressors and hyperhydration therapy were administered. Computed tomography did not reveal a cause of the cardiac arrest. Antibiotics were initiated after obtaining blood culture samples. The patient was admitted to the intensive care unit (ICU). High-dose vasopressors and hyperhydration therapy were continued and fresh frozen plasma was transfused. Two hours after ICU admission, gram staining of a blood smear revealed the presence of Streptococcus, and the antibiotics were switched to penicillin G potassium and clindamycin, and immunoglobulins were administered. Extracorporeal membrane oxygenation was initiated 10 h after ICU admission owing to respiratory failure caused by fluid overload; however, the patient's condition did not improve and she died 40 h after admission. Blood culture results confirmed the presence of Streptococcus pyogenes; the T and M serotypes were unclassifiable. The emm genotype was emm22. Sequencing revealed the presence of streptococcal pyrogenic toxin genes, speA and speB, whereas speC was absent. CsrS, CsrR, and Rgg amino acid sequencing revealed the presence of a CsrS mutation.

A Case of Necrotizing Fasciitis/Myositis and Streptococcal Toxic Shock Syndrome Caused by emm22/ST46 Strain of Streptococcus pyogenes

Streptococcus pyogenes, also known as Group A Streptococcus (GAS), can cause severe invasive diseases with high fatality rates. We report a case of necrotizing fasciitis and myositis complicated by Streptococcal Toxic Shock-Like Syndrome (STSS) caused by the invasive emm22/ST46 strain of Streptococcus pyogenes in China. A previously healthy 57-year-old Chinese Canadian man presented with right calf pain and ulceration following a hike in the Gobi Desert, which progressed to unconsciousness and severe infection. Despite initial treatment, his condition deteriorated, leading to his transfer to our intensive care unit. Metagenomic Next-Generation Sequencing identified Streptococcus pyogenes, and antimicrobial susceptibility testing revealed resistance to erythromycin, tetracycline, and clindamycin. Despite broad-spectrum antimicrobial therapy, debridement, and supportive measures, the patient's condition necessitated amputation of the right lower limb. He recovered and was discharged from the hospital on Day 43. Whole-genome sequencing of the isolate identified 15 multiple virulence factors. Phylogenetic analysis revealed that the closest relative of the isolate was a strain identified in China. This case underscores the importance of early recognition and treatment of invasive GAS infections to prevent severe outcomes, and we should pay attention to invasive emm22/ST46 GAS infections in China.

Presence of Group A streptococcus frequently assayed virulence genes in invasive disease: a systematic review and meta-analysis

Introduction

It is currently unclear what the role of Group A streptococcus (GAS) virulence factors (VFs) is in contributing to the invasive potential of GAS. This work investigated the evidence for the association of GAS VFs with invasive disease.

Methods

We employed a broad search strategy for studies reporting the presence of GAS VFs in invasive and non-invasive GAS disease. Data were independently extracted by two reviewers, quality assessed, and meta-analyzed using Stata®.

Results

A total of 32 studies reported on 45 putative virulence factors [invasive (n = 3,236); non-invasive (n = 5,218)], characterized by polymerase chain reaction (PCR) (n = 30) and whole-genome sequencing (WGS) (n = 2). The risk of bias was rated as low and moderate, in 23 and 9 studies, respectively. Meta-,analyses of high-quality studies (n = 23) revealed a significant association of speM [OR, 1.64 (95%CI, 1.06; 2.52)] with invasive infection. Meta-analysis of WGS studies demonstrated a significant association of hasA [OR, 1.91 (95%CI, 1.36; 2.67)] and speG [OR, 2.83 (95%CI, 1.63; 4.92)] with invasive GAS (iGAS). Meta-analysis of PCR studies indicated a significant association of speA [OR, 1.59 (95%CI, 1.10; 2.30)] and speK [OR, 2.95 (95%CI, 1.81; 4.80)] with invasive infection. A significant inverse association was observed between prtf1 [OR, 0.42 (95%CI, 0.20; 0.87)] and invasive infection.

Conclusion

This systematic review and genomic meta-analysis provides evidence of a statistically significant association with invasive infection for the hasA gene, while smeZ, ssa, pnga3, sda1, sic, and NaDase show statistically significantly inverse associations with invasive infection. SpeA, speK, and speG are associated with GAS virulence; however, it is unclear if they are markers of invasive infection. This work could possibly aid in developing preventative strategies.

Increase in invasive group A streptococcal infections (iGAS) in children and older adults, Norway, 2022 to 2024

At the end of 2022 and most notably during the first half of 2023, the number of invasive group A streptococcus (iGAS) notifications increased in Norway, largely affecting children younger than 10 years, as observed in several other countries. Following this atypical season, a new surge in the number of iGAS notifications began in December 2023 and peaked between January and February 2024, now particularly affecting both children younger than 10 years and older adults (70 years and above).

Global Streptococcus pyogenes strain diversity, disease associations, and implications for vaccine development: a systematic review

The high strain diversity of Streptococcus pyogenes serves as a major obstacle to vaccine development against this leading global pathogen. We did a systematic review of studies in PubMed, MEDLINE, and Embase that reported the global distribution of S pyogenes emm-types and emm-clusters from Jan 1, 1990, to Feb 23, 2023. 212 datasets were included from 55 countries, encompassing 74 468 bacterial isolates belonging to 211 emm-types. Globally, an inverse correlation was observed between strain diversity and the UNDP Human Development Index (HDI; r=-0·72; p<0·0001), which remained consistent upon subanalysis by global region and site of infection. Greater strain diversity was associated with a lower HDI, suggesting the role of social determinants in diseases caused by S pyogenes. We used a population-weighted analysis to adjust for the disproportionate number of epidemiological studies from high-income countries and identified 15 key representative isolates as vaccine targets. Strong strain type associations were observed between the site of infection (invasive, skin, and throat) and several streptococcal lineages. In conclusion, the development of a truly global vaccine to reduce the immense burden of diseases caused by S pyogenes should consider the multidimensional diversity of the pathogen, including its social and environmental context, and not merely its geographical distribution.

Risk Factors for Predicting Mortality and Amputation of Patients with Necrotizing Soft-Tissue Infections: Retrospective Analysis of 111 Cases from a Single Medical Center

Objective

Necrotizing soft-tissue infections (NSTIs) are rare clinical infections with surgical emergencies having a high mortality rate. This study aimed to investigate risk factors for mortality and amputation of patients with NSTI.

Methods

We retrospectively analyzed critical factors for outcomes of 111 patients with NSTI hospitalized in our department from 1 January 1999 to 31 December 2018. NSTI diagnosis was based on the patient's clinical characteristics, laboratory risk indicator for necrotizing fasciitis (LRINEC) score, laboratory test data, and microbiological findings in blood and wound culture. The risk factors for mortality and amputation of NSTI were determined using univariate or multivariate logistic regression analysis, receiver operating characteristics (ROC), and the area under the ROC curve (AUC) at 90 days after admission.

Results

Diagnosis of 111 patients with NSTI was confirmed according to clinical features, LRINEC score, image data, laboratory findings, and microorganism culture in blood and wounds. The mortality rate was 9.91% (11/111) at day 90 follow-up. High white blood cell (WBC), low hematocrit (HCT), and multiple surgeries were identified to be critical risk factors for NSTI mortality in univariate and multivariate logistic analyses. AUCs, 95% confidence intervals (CI), and P values of risk factors were 0.699, 0.54-0.95, and P = 0.0117 for high WBC; 0.788, 0.63-0.97, and P = 0.0006 for low HCT; and 0.745, 0.59-0.90, and P = 0.0018 for multiple surgeries, respectively. These patients also had high LRINEC scores. Amputation occurred in 34.23% (38/111) of patients. Risk factors for amputation were higher age, low hemoglobin (Hb), and multiple wounds. AUCs, 95% confidence intervals (CI), and P values were 0.713, 0.11-0.32, and P < 0.0001 for higher age; 0.798, 0.08-0.29, and P=0.0007 for low Hb; and 0.757, 0.17-0.34, and P  < 0.0001 for multiple lesion sites, respectively.

Conclusions

High LRINEC scores, high WBC, low HCT, and multiple surgeries were relevant to increased mortality. Higher age, low Hb, and multiple wounds were associated with amputation risk. These clinical features must be paid attention to when patients are diagnosed with NSTI.

Changes in Group A Streptococcus emm Types Associated with Invasive Infections in Adults, Spain, 2023

An increase in invasive group A Streptococcus infection was detected in the northeast of Spain in November 2022. A postpandemic decline in the diversity of circulating emm types involved in invasive group A Streptococcus was observed, along with the emergence of emm49 in this geographic area.

The effect of hyperbaric oxygen therapy on the clinical outcomes of necrotizing soft tissue infections: a systematic review and meta-analysis

BACKGROUND

To determine the efficacy of hyperbaric oxygen therapy (HBO) in the treatment of necrotizing soft tissue infections (NSTI), we conducted a meta-analysis of the available evidence.

METHODS

Data sources were PubMed, Embase, Web of Science, Cochrane Library, and reference lists. The study included observational trials that compared HBO with non-HBO, or standard care. The primary outcome was the mortality rate. Secondary outcomes were the number of debridement, amputation rate and complication rate. Relative risks or standardized mean differences with 95% confidence intervals were calculated for dichotomous and continuous outcomes, respectively.

RESULTS

A total of retrospective cohort and case-control studies were included, including 49,152 patients, 1448 who received HBO and 47,704 in control. The mortality rate in the HBO group was significantly lower than that in the non-HBO group [RR = 0.522, 95% CI (0.403, 0.677), p < 0.05]. However, the number of debridements performed in the HBO group was higher than in the non-HBO group [SMD = 0.611, 95% CI (0.012, 1.211), p < 0.05]. There was no significant difference in amputation rates between the two groups [RR = 0.836, 95% CI (0.619, 1.129), p > 0.05]. In terms of complications, the incidence of MODS was lower in the HBO group than in the non-HBO group [RR = 0.205, 95% CI (0.164, 0.256), p < 0.05]. There was no significant difference in the incidence of other complications, such as sepsis, shock, myocardial infarction, pulmonary embolism, and pneumonia, between the two groups (p > 0.05).

CONCLUSION

The current evidence suggests that the use of HBO in the treatment of NSTI can significantly reduce the mortality rates and the incidence rates of complications. However, due to the retrospective nature of the studies, the evidence is weak, and further research is needed to establish its efficacy. It is also important to note that HBO is not available in all hospitals, and its use should be carefully considered based on the patient's individual circumstances. Additionally, it is still worthwhile to stress the significance of promptly evaluating surgical risks to prevent missing the optimal treatment time.

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.

Retroperitoneal necrotizing soft tissue infections: A case report and literature review

Necrotizing soft tissue infections of the retroperitoneal is a rare disease identity. Here we present a 50-year-old male patient who underwent surgical exploration for retroperitoneal necrotizing soft tissue infection. Postoperatively, he was put on broad-spectrum antibiotics. He passed on after the first exploration and debridement.

A global snapshot on the prevalent macrolide-resistant emm types of Group A Streptococcus worldwide, their phenotypes and their resistance marker genotypes during the last two decades: A systematic review

Watchful epidemiological surveillance of macrolide-resistant Group A Streptococcus (MRGAS) clones is important owing to the evolutionary and epidemiological dynamic of GAS. Meanwhile, data on the global distribution of MRGAS emm types according to macrolide resistance phenotypes and genotypes are scant and need to be updated. For this, the present systematic review analyses a global set of extensively characterized MRGAS isolates from patients of diverse ages and clinical presentations over approximately two decades (2000 to 2020) and recaps the peculiar epidemiological features of the dominant MRGAS clones. Based on the inclusion and exclusion criteria, 53 articles (3593 macrolide-resistant and 15,951 susceptible isolates) distributed over 23 countries were dissected with a predominance of high-income countries over low-income ones. Although macrolide resistance in GAS is highly variable in different countries, its within-GAS distribution seems not to be random. emm pattern E, 13 major emm types (emm12, 4, 28, 77, 75, 11, 22, 92, 58, 60, 94, 63, 114) and 4 emm clusters (A-C4, E1, E6, and E2) were significantly associated with macrolide resistance. emm patterns A-C and D, 14 major emm types (emm89, 3, 6, 2, 44, 82, 87, 118, 5, 49, 81, 59, 227, 78) and 3 well-defined emm clusters (A-C5, E3, and D4) were significantly associated with macrolide susceptibility. Scrutinizing the tendency of each MRGAS emm type to be significantly associated with specific macrolide resistance phenotype or genotype, interesting vignettes are also unveiled. The 30-valent vaccine covers ~95% of MRGAS isolates. The presented data urge the importance of comprehensive nationwide sustained surveillance of MRGAS circulating clones particularly in Low and Middle income countries where sampling bias is high and GAS epidemiology is obfuscated and needs to be demystified.

Racial and Socioeconomic Disparities in Necrotizing Soft-Tissue Infection

Necrotizing soft-tissue infection (NSTI) is a medical emergency. We investigated the impact of racial, socioeconomic disparities, and comorbidities on mortality, complications, length of stay, and charges in patients with NSTI.

Data were acquired from the National Inpatient Sample from Q4 2015 to 2017. ICD-10, Clinical Modification codes were utilized to identify relevant cases. Logistic regression was used to assess socioeconomic, racial, and health risk factors for adverse outcomes in NSTI patients.

Of 16,071,053 cases identified during the study period, 15,078 (0.094%) NSTI cases were recognized. Black patients had increased odds of amputation (OR 1.40 95% CI 1.24-1.58, p < 0.001), prolonged hospital stay (OR 1.40 95% CI 1.24-1.58, p < 0.001), excessive charges (OR 1.22 95% CI 1.03-1.43, p = 0.019), and adverse discharge disposition (OR 1.32 95% CI 1.19-1.46, p < 0.001) compared to white patients. Hispanic patients had increased odds of mortality (OR 1.30 95% CI 1.05-1.60, p = 0.014) and amputation (OR 1.21 95% CI 1.04-1.42, p = 0.016) compared to white patients. Medicare patients had increased odds of mortality (OR 1.35 95% CI 1.09-1.67, p = 0.006), Medicaid patients had increased odd of amputation (OR 1.33 95% CI 1.17-1.51, p < 0.001) and prolonged LOS (OR 1.33 95% CI 1.17-1.51, p < 0.001). Patients in the lower income quartiles had decreased odds of amputation compared to the highest income quartile, including the 26^th to 50^th income quartile (OR 0.84 95% CI 0.73-0.98, p = 0.022) and 51^st to 75^th income quartile (OR 0.84 95% CI 0.73-0.98, p = 0.022).

Racial and socioeconomic disparities exist for patients being treated for NSTIs.

Consistent Biofilm Formation by Streptococcus pyogenes emm 1 Isolated From Patients With Necrotizing Soft Tissue Infections

Objectives

Biofilm formation has been demonstrated in muscle and soft tissue samples from patients with necrotizing soft tissue infection (NSTI) caused by Streptococcus pyogenes, but the clinical importance of this observation is not clear. Although M-protein has been shown to be important for in vitro biofilm formation in S. pyogenes, the evidence for an association between emm type and biofilm forming capacity is conflicting. Here we characterize the biofilm forming capacity in a collection of S. pyogenes isolates causing NSTI, and relate this to emm type of the isolates and clinical characteristics of the patients.

Methods

Bacterial isolates and clinical data were obtained from NSTI patients enrolled in a multicenter prospective observational study. Biofilm forming capacity was determined using a microtiter plate assay.

Results

Among 57 cases, the three most frequently encountered emm types were emm1 (n = 22), emm3 (n = 13), and emm28 (n = 7). The distribution of biofilm forming capacity in emm1 was qualitatively (narrow-ranged normal distribution) and quantitatively (21/22 isolates in the intermediate range) different from other emm types (wide ranged, multimodal distribution with 5/35 isolates in the same range as emm1). There were no significant associations between biofilm forming capacity and clinical characteristics of the patients.

Conclusions

The biofilm forming capacity of emm1 isolates was uniform and differed significantly from other emm types. The impact of biofilm formation in NSTI caused by S. pyogenes on clinical outcomes remains uncertain.

Necrotizing Soft-Tissue Infections After Hip Arthroplasty

Necrotizing soft-tissue infections are a rare complication following hip arthroplasty procedures. These rapidly spreading infections have a high mortality rate and must be diagnosed and treated in an expeditious manner. This article discusses the epidemiology, classification, diagnosis, and treatment of these conditions and describes 2 related case reports.

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.

Deciphering mobile genetic elements disseminating macrolide resistance in Streptococcus pyogenes over a 21 year period in Barcelona, Spain

OBJECTIVES

To phenotypically and genetically characterize the antibiotic resistance determinants and associated mobile genetic elements (MGEs) among macrolide-resistant (MR) Streptococcus pyogenes [Group A streptococci (GAS)] clinical isolates collected in Barcelona, Spain.

METHODS

Antibiotic susceptibility testing was performed by microdilution. Isolates were emm and MLST typed and 55 were whole-genome sequenced to determine the nature of the macrolide resistance (MR) determinants and their larger MGE and chromosomal context.

RESULTS

Between 1998 and 2018, 142 of 1028 GAS (13.8%) were MR. Among 108 isolates available for molecular characterization, 41.7% had cMLSB, 30.5% iMLSB and 27.8% M phenotype. Eight erm(B)-containing strains were notable in having an MDR phenotype conferred by an MGE encoding several antibiotic resistance genes. MR isolates were comprised of several distinct genetic lineages as defined by the combination of emm and ST. Although most lineages were only transiently present, the emm11/ST403 clone persisted throughout the period. Two lineages, emm9/ST75 with erm(B) and emm77/ST63 with erm(TR), emerged in 2016-18. The erm(B) was predominantly encoded on the Tn916 family of transposons (21/31) with different genetic contexts, and in other MGEs (Tn6263, ICESpHKU372 and one harbouring an MDR cluster called ICESp1070HUB). The erm(TR) was found in ICESp2905 (8/17), ICESp1108-like (4/17), ICESpHKU165 (3/17) and two structures described in this study (IMESp316HUB and ICESp3729HUB). The M phenotype [mef(A)-msr(D)] was linked to phage φ1207.3. Eight integrative conjugative element/integrative mobilizable element (ICE/IME) cluster groups were classified on the basis of gene content within conjugation modules. These groups were found among MGEs, which corresponded with the MR-containing element or the site of integration.

CONCLUSIONS

We detected several different MGEs harbouring erm(B) or erm(TR). This is the first known description of Tn6263 in GAS and three MGEs [IMESp316HUB, ICESp3729HUB and ICESp1070HUB] associated with MR. Periods of high MR rates in our area were mainly associated with the expansion of certain predominant lineages, while in low MR periods different sporadic and low prevalence lineages were more frequent.

Invasive Streptococcus pyogenes disease in Spain: a microbiological and epidemiological study covering the period 2007-2019

The aim of this study is to present the first nationwide microbiological and epidemiological study of invasive group A Streptococcus (iGAS) disease in Spain. One thousand eight hundred ninety-three iGAS isolates were analyzed over 2007-2019. emm typing was performed by sequencing the gene's variable 5' end, exotoxin genes were identified by PCR, and antimicrobial susceptibility explored via the E test and disk diffusion. Five hundred twenty-three isolates were associated with sepsis, 292 with cellulitis, 232 with scarlet fever, 153 with pneumonia, 141 with streptococcal toxic shock syndrome, and 94 with necrotizing fasciitis. The most prevalent emm types were emm1 (449/1893 isolates), emm89 (210/1893), emm3 (208/1893), emm4 (150/1893), emm12 (112/1893) emm6 (107/1893), emm87 (89/1893), emm28 (88/1893), emm75 (78/1893), emm77 (78/1893), emm11 (58/1893), and emm22 (35/1893). emm1, emm3, emm4, and emm6 were the predominant types affecting children (mostly respiratory infections), while emm11, emm77, and emm89 prevailed in the elderly (mostly skin infections). Each emm type was associated with one or more exotoxin gene (spe, sme, and ssa) profiles. speA was detected in 660 isolates, speB in 1829, speC in 1014, speF in 1826, speG in 1651, speJ in 716, speH in 331, smeZ in 720, and ssa in 512. Isolates with speA were associated with the most severe infections. Penicillin susceptibility was universal. Two hundred twenty-four isolates were resistant to tetracycline, 169 to erythromycin, and 81 to clindamycin. Tetracycline, erythromycin, and clindamycin resistance rates declined over the study period. The above information could serve as the basis for continued surveillance efforts designed to control disease cause by this bacterium.

Prognostic factors for mortality in 123 severe cases of necrotizing fasciitis in 5 hospitals in the Netherlands between 2003 and 2017

Purpose

Necrotizing fasciitis (NF) is a severe soft tissue infection with a high morbidity and mortality. With early diagnosis and treatment this could be reduced. Unfortunately, the diagnosis of necrotizing fasciitis can be very difficult. In recent years many risk factors have been identified. In 2004, the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score was developed. A tool that could help diagnosing NF. In this study, we search for prognostic factors for mortality in necrotizing fasciitis.

Methods

All adult patients with histopathological or surgical confirmed NF needed to be admitted to the intensive care unit for at least 24 h between January 2003 and December 2017 in five hospitals from the Nijmegen teaching region were included. We excluded patients with other forms of soft tissue infections or patients with an intensive care unit (ICU) stay of < 24 h because we exclusively wanted to include patients with a fulminant course of necrotizing fasciitis.

Results

We have included 123 cases. The overall mortality was 31.7% (N = 39). The overall mean LRINEC score was 7.4 ± 2.7. Patients who died as the result of NF had a significantly higher median LRINEC score (8 vs. 7, p = 0.034). Other parameters found to be associated with mortality are age ≥ 60 years, cardiovascular disease in the medical history, ≥ 2 comorbidities, and lactate level greater than 1.7 mmol/L.

Conclusion

LRINEC score should be calculated in all patients presenting with NF to provide an additional source for clinical outcome. A high LRINEC score could implicate a higher risk of mortality. Especially in elderly patients, with a cardiac history, more than two comorbidities or a lactate level greater than 1.7 mmol/L.

Risk Factors and Predictors of Mortality in Streptococcal Necrotizing Soft-tissue Infections: A Multicenter Prospective Study

BACKGROUND

Necrotizing soft-tissue infections (NSTI) are life-threatening conditions often caused by β-hemolytic streptococci, group A Streptococcus (GAS) in particular. Optimal treatment is contentious. The INFECT cohort includes the largest set of prospectively enrolled streptococcal NSTI cases to date.

METHODS

From the INFECT cohort of 409 adults admitted with NSTI to 5 clinical centers in Scandinavia, patients culture-positive for GAS or Streptococcus dysgalactiae (SD) were selected. Risk factors were identified by comparison with a cohort of nonnecrotizing streptococcal cellulitis. The impact of baseline factors and treatment on 90-day mortality was explored using Lasso regression. Whole-genome sequencing of bacterial isolates was used for emm typing and virulence gene profiling.

RESULTS

The 126 GAS NSTI cases and 27 cases caused by SD constituted 31% and 7% of the whole NSTI cohort, respectively. When comparing to nonnecrotizing streptococcal cellulitis, streptococcal NSTI was associated to blunt trauma, absence of preexisting skin lesions, and a lower body mass index. Septic shock was significantly more frequent in GAS (65%) compared to SD (41%) and polymicrobial, nonstreptococcal NSTI (46%). Age, male sex, septic shock, and no administration of intravenous immunoglobulin (IVIG) were among factors associated with 90-day mortality. Predominant emm types were emm1, emm3, and emm28 in GAS and stG62647 in SD.

CONCLUSIONS

Streptococcal NSTI was associated with several risk factors, including blunt trauma. Septic shock was more frequent in NSTI caused by GAS than in cases due to SD. Factors associated with mortality in GAS NSTI included age, septic shock, and no administration of IVIG.

Necrotizing Soft Tissue Infections in Intensive Care

Background:

Necrotizing soft tissue infections (NSTIs) are typically characterized by extensive soft tissue destruction with systemic signs of toxicity, ranging from sepsis to septic shock. Our aim was to analyze the clinical characteristics, microbiological results, laboratory data, therapies, and outcome of patients with NSTIs admitted to an intensive care unit (ICU).

Methods:

A monocentric observational study of patients admitted to the ICU of a university hospital between January 2009 and December 2017. The demographic characteristics, comorbidities, clinical features, microbiology and laboratory results, organ dysfunctions, therapies, and outcome were retrospectively analyzed.

Results:

There were 59 patients and 70% males. The mean age (± SD) was 55 ± 18; type II (monomicrobial) NSTI was present in 36 patients (61%); the most common isolated pathogen was Streptococcus pyogenes in 28 patients (48%). Septic shock was diagnosed in 41 patients (70%). The most common organ dysfunctions were circulatory and renal in 42 (71%) and 38 patients (64%). The mean value (± SD) of serum lactate at admission to the ICU was 4.22 ± 5.42 mmol/l, the median SOFA score and SAPS II were 7 (IQR 4 - 10) and 46 (IQR 30.5 - 53). ICU mortality rate was 25%. Both SOFA score and serum lactate demonstrated a good prognostic value regarding ICU outcome (OR 1.29, 95%CI 1.07-1.57, P < 0.007 and OR 1.53, 95%CI 1.19-1.98, P < 0.001). A cut-off value for serum lactate of 6.55 mmol/L positively predicted mortality with 67% sensitivity and 97% specificity.

Conclusion:

NSTIs carry a high risk of septic shock and multiple organ dysfunction syndrome and thus are still associated with high mortality. In our study, the value of serum lactate at admission to the ICU correlated well with mortality. This easy-to-measure parameter could play a role in the decision-making process regarding prognosis and continuation of care.

Diverse disease processes of group A Streptococcus infection including severe invasive infections among members of a family

We herein report three cases of group A Streptococcus (GAS) infection in a family. Patient 1, a 50-year-old woman, was transferred to our hospital in shock with acute respiratory distress syndrome, swelling in the right neck and erythemata on both lower extremities. She required intubation because of laryngeal oedema. At the same time, patient 2, a 48-year-old man, was admitted because of septic shock, pneumonia and a pulmonary abscess. Five days later, patient 3, a 91-year-old woman, visited our clinic with bloody stool. All three patients were cured by antibiotics, and GAS was detected by specimen cultures. During these patients' clinical course, an 84-year-old woman was found dead at home after having been diagnosed with type A influenza. All four patients lived in the same apartment. The GAS genotypes detected in the first three patients were identical. When treating patients with GAS, appropriate management of close contacts is mandatory.

Risk factors associated with necrotizing fasciitis of the lower limbs: A multicenter case-control study

OBJECTIVE

The aim of this case-control study was to identify risk factors associated with necrotizing fasciitis (NF) of the lower limbs.

PATIENTS AND METHODS

We conducted a prospective case-control study in hospital dermatology departments in 5 sub-Saharan African countries over a 2-year period (April 2017 to July 2019). The cases were patients with NF of the lower limbs and the controls were patients with leg erysipelas. Each case was matched with two controls for age (±5 years) and sex. We analyzed local and general factors.

RESULTS

During the study period, 159 cases (73 females, 86 males) were matched with 318 controls. The mean age was 48.5±15.8 years for cases and 46.5±16.2 years for controls (P=0.24). The main local signs of NF were cutaneous necrosis (83.7%), pain (75.5%) and induration (42.1%). Multivariate analysis showed the following to be independent risk factors associated with NF of the lower limbs: obesity (odds ratio [OR]=2.10; 95% confidence interval [CI]: 1.21-3.42), diabetes (OR=3.97; 95% CI: 1.95-6.13), nicotine addiction (OR=5.07; 95% CI: 2.20-11.70), use of non-steroidal anti-inflammatory drugs (NSAIDs) (OR=7.85; 95% CI 4.60-14.21) and voluntary cosmetic depigmentation (OR=2.29; 95% CI: 1.19-3.73).

CONCLUSION

Our study documents the role of NSAID use at the onset of symptoms as a risk factor for NF of the lower limbs. However, the originality of our study consists in the identification of voluntary cosmetic depigmentation as a risk factor for NF of the lower limbs in sub-Saharan Africa patients. Our results also identified typical overarching factors such as diabetes, obesity and nicotine addiction. Knowing these factors and taking them into account will enable optimization of management strategies for these conditions.

Necrotizing fasciitis, causative agents and management: a five-year retrospective study in two tertiary care hospitals in Central Malaysia

PURPOSE

Necrotizing fasciitis (NF) is a rapidly progressive inflammatory infection of the fascia, with secondary necrosis of the subcutaneous tissues. The severity of the disease depends on the virulence of the organism and host immunity. There is a paucity of reports on the prevalence of NF causing pathogens and management.

METHODS

Retrospective data of patients treated for NF were collected from two tertiary care hospitals in Central Malaysia between January 2014 and December 2018.

RESULTS

A total of 469 NF patients were identified. More than half of the NF patients were males (n = 278; 59.28%). The highest number of cases was found among age groups between 30 and 79, with mean age of 56.17. The majority of the NF cases (n = 402; 85.72%) were monomicrobial. Streptococcus spp. (n = 89; 18.98%), Pseudomonas aeruginosa (n = 63; 13.44%) and Staphylococcus spp. (n = 61; 13.01%) were identified as the top three microorganisms isolated. Among the 469 NF cases, 173 (36.8%) were amputated or dead while 296 (63.1%) recovered. Proteus spp. (n = 19; 12.93%), Klebsiella pneumoniae (n = 18; 12.24%) and Escherichia coli (n = 14; 9.52%) were associated with all types of amputations. The most common antibiotic prescribed was unasyn (n = 284; 60.56%), followed by clindamycin (n = 56; 11.94%) and ceftazidime (n = 41; 8.74%). A total of 239 (61.8%) recovered while 148 (38.2%) were either amputated or dead when managed with the unasyn, clindamycin or ceftazidime.

CONCLUSION

This study represents the largest NF cases series in Malaysia highlighting the causative agents and management.

Pathogenic Mechanisms of Streptococcal Necrotizing Soft Tissue Infections

Necrotizing skin and soft tissue infections (NSTIs) are severe life-threatening and rapidly progressing infections. Beta-hemolytic streptococci, particularly S. pyogenes (group A streptococci (GAS)) but also S. dysgalactiae subsp. equisimilis (SDSE, most group G and C streptococcus), are the main causative agents of monomicrobial NSTIs and certain types, such as emm1 and emm3, are over-represented in NSTI cases. An arsenal of bacterial virulence factors contribute to disease pathogenesis, which is a complex and multifactorial process. In this chapter, we summarize data that have provided mechanistic and immuno-pathologic insight into host-pathogens interactions that contribute to tissue pathology in streptococcal NSTIs. The role of streptococcal surface associated and secreted factors contributing to the hyper-inflammatory state and immune evasion, bacterial load in the tissue and persistence strategies, including intracellular survival and biofilm formation, as well as strategies to mimic NSTIs in vitro are discussed.

Evaluation of the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score for detecting necrotizing soft tissue infections in patients with diabetes and lower extremity infection

AIMS

The aim of this pilot study was to assess the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC), a scoring system for Necrotizing Soft Tissue Infections, to diagnose Necrotizing Soft Tissue Infections of the lower extremity in patients with diabetes.

METHODS

Sixty-nine patients with lower extremity infections were prospectively enrolled. The Laboratory Risk Indicator for Necrotizing Fasciitis was calculated and logistic regression was performed for each laboratory value.

RESULTS

The Laboratory Risk Indicator for Necrotizing Fasciitis was associated with Necrotizing Soft Tissue Infection diagnosis in patients with diabetes (p = 0.01). Sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 69%, 16.6%, and 100% respectively. Elevated C-reactive protein (OR 1.01, p = 0.02, 95% CI [1.002-1.23]) and white blood cell count (OR 1.34, p < 0.01, 95% CI [1.1-1.7]) were associated with Necrotizing Soft Tissue Infection.

CONCLUSIONS

The Laboratory Risk Indicator for Necrotizing Fasciitis was useful as a negative predictor of Necrotizing Soft Tissue Infection while C- reactive protein and white blood cell count may have value as individual predictors. We recommend high clinical suspicion of Necrotizing Soft Tissue Infections in diabetics as laboratory evaluation may be non-specific.

Spontaneous Necrotizing Fasciitis

Necrotizing soft tissue infections typically begin with direct inoculation of bacteria into the subcutaneous tissues. Here, we present a case with no such exposure, but with severe necrotizing fasciitis. We present a middle-aged man presented to the emergency department for a presumed allergic reaction after having initially sought care twice at an urgent care facility. The patient had swelling, but no tenderness of his right lateral chest and flank. Subsequent imaging showed extensive fluid in the fascial planes of the right chest wall requiring surgical debridement. Necrotizing fasciitis that is not treated with surgical debridement carries a mortality rate approaching 100%. This case highlights a potential atypical presentation as well as highlights the fact that the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score lacks sensitivity to rule out a necrotizing soft tissue infection, requiring surgical debridement for diagnosis.

Incidence, comorbidity and mortality in patients with necrotising soft-tissue infections, 2005-2018: a Danish nationwide register-based cohort study

OBJECTIVE

To assess the incidence, comorbidities, treatment modalities and mortality in patients with necrotising soft-tissue infections (NSTIs) in Denmark.

DESIGN

Nationwide population-based registry study.

SETTING

Denmark.

PARTICIPANTS

Danish residents with NSTI between 1 January 2005 and 31 August 2018.

MAIN OUTCOME MEASURE

Incidence of disease per 100 000 person/year and all-cause mortality at day 90 obtained from Danish National Patient Registry and the Danish Civil Registration System.

RESULTS

1527 patients with NSTI were identified, yielding an incidence of 1.99 per 100 000 person/year. All-cause 30-day, 90-day and 1-year mortality were 19.4% (95% CI 17.4% to 21.5%), 25.2% (95% CI 23.1% to 27.5%) and 30.4% (95% CI 28.0% to 32.8%), respectively. Amputation occurred in 7% of the individuals. Diabetes was the most predominant comorbidity affecting 43% of the cohort, while 26% had no comorbidities. Higher age, female sex and increasing comorbidity index were found to be independent risk factors of mortality. Admission to high-volume hospitals was associated with improved survival (OR 0.59, 95% CI 0.45 to 0.77). Thirty-six per cent received hyperbaric oxygen therapy (HBOT) as an adjunctive therapy. No change in overall mortality was found over the studied time period.

CONCLUSION

The present study found that in Denmark, the incidence of NSTI increased; mortality rates remained high and largely unaltered. Diabetes was the most common comorbidity, while higher age, female sex and increasing comorbidity index were associated to increased mortality. Survival was improved in those admitted to hospitals with more expertise in treating NSTI. In high-volume hospital, HBOT was associated with decreased odds for mortality.

Epidemiological Situation of Necrotizing Fasciitis and Factors in Thailand and Factors Associated with Its Morbidity and Mortality, 2014-2018

INTRODUCTION

Necrotizing fasciitis (NF) is a rare skin and soft-tissue bacterial infection with high morbidity and mortality. Knowledge about the prevalence and incidence of NF in Thailand is quite sparse. The objective of this study was to determine the prevalence of NF in Thailand and factors that may be potentially associated with NF morbidity and mortality.

METHODS

A cross-sectional study using secondary data from Thailand's national health databases between 2014 and 2018 was conducted. Descriptive statistics using median and percentage formats were used. This was complemented by multivariable logistic regression to determine the association between various factors (such as age and underlying diseases) with NF morbidity and mortality. Univariate spatial data analysis was exercised to identify the geographical hot spots in which the disease appeared.

RESULTS

During 2014-2018, we found 90,683 NF cases. About 4.86% of the cases died. The median age for all cases was 59.39 years old. The annual incidence of NF demonstrated an upward trend (from 26.08 per 100,000 population in 2014 to 32.64 per 100,000 population in 2018). The monthly incidence was highest between May and August. A high incidence cluster (as indicated by local Moran's I) was found in the north-eastern region of Thailand. The most infected sites were on the ankles and feet (43.18%) with an amputation rate of 7.99% in all cases. Multivariable logistic regression indicated that the significant risk factor for amputation was a presence of underlying diseases, namely diabetes (OR 7.94, 95% CI 7.34-8.61). Risk factors for mortality included being elderly (OR 1.82, 95% CI 1.68-1.98) and a presence of underlying hypertension (OR 1.16, 95% CI 1.07-1.27), cirrhosis (OR 4.67, 95% CI 4.17-5.21), and malignancy (OR 1.88, 95% CI 1.55-2.26).

DISCUSSION AND CONCLUSION

As the elderly and those with chronic underlying diseases are likely to face non-preferable health outcomes from NF, healthcare providers should pay great attention to these groups of patients. Early and intensive treatment might be considered in these groups of patients. Further studies that aim to validate the volume of actual NF cases and reported NF cases are recommended.

Genetic evolution of invasive emm28 Streptococcus pyogenes strains and significant association with puerperal infections in young women in Finland

OBJECTIVES

Streptococcus pyogenes or group A streptococcus (GAS) is a human specific pathogen that annually infects over 700 million individuals. GAS strains of type emm28 are an abundant cause of invasive infections in Europe and North America.

METHODS

We conducted a population-based study on bacteraemic emm28 GAS cases in Finland, from 1995 to 2015. Whole-genome sequencing (WGS) was used to genetically characterize the bacterial isolates. Bayesian analysis of the population structure was used to define genetic clades. Register-linkage analysis was performed to test for association of emm28 GAS with delivery- or postpartum-related infections. A genome-wide association study was used to search for DNA sequences associated with delivery or puerperal infections.

RESULTS

Among 3060 bacteraemic cases reported during the study period, 714 were caused by emm28. Women comprised a majority of cases (59 %, 422/714), and were significantly over-represented (84.4 %, 162/192, p < 0.0001) among cases in the childbearing age group (20-40 years). Register-linkage analysis revealed strong association (p < 0.0001) of emm28 bacteraemias with delivery and puerperium. In this register-linkage analysis, 120 women with GAS bacteraemia were identified and linked to delivery, infections during delivery or puerperium time. Among these the proportion of cases caused by emm28 was significantly higher than any other emm type (55.8%, 67/120, p < 0.0001). Among the four genetic subclades identified, SC1B has dominated among the bacteraemic cases since 2000. Altogether 620 of 653 (94.9%) isolates belonged to SC1B. No specific sequence or genetic clade was found nonrandomly associated with delivery or puerperal infections.

CONCLUSIONS

Women of childbearing age were significantly overrepresented among bacteraemic emm28 GAS cases, and in particular were strongly associated with delivery and puerperium cases over the 21 years studied. The molecular mechanisms behind these associations are unclear and warrant further investigation.

Genetic heterogeneity of the Spy1336/R28-Spy1337 virulence axis in Streptococcus pyogenes and effect on gene transcript levels and pathogenesis

Streptococcus pyogenes is a strict human pathogen responsible for more than 700 million infections annually worldwide. Strains of serotype M28 S. pyogenes are typically among the five more abundant types causing invasive infections and pharyngitis in adults and children. Type M28 strains also have an unusual propensity to cause puerperal sepsis and neonatal disease. We recently discovered that a one-nucleotide indel in an intergenic homopolymeric tract located between genes Spy1336/R28 and Spy1337 altered virulence in a mouse model of infection. In the present study, we analyzed size variation in this homopolymeric tract and determined the extent of heterogeneity in the number of tandemly-repeated 79-amino acid domains in the coding region of Spy1336/R28 in large samples of strains recovered from humans with invasive infections. Both repeat sequence elements are highly polymorphic in natural populations of M28 strains. Variation in the homopolymeric tract results in (i) changes in transcript levels of Spy1336/R28 and Spy1337 in vitro, (ii) differences in virulence in a mouse model of necrotizing myositis, and (iii) global transcriptome changes as shown by RNAseq analysis of isogenic mutant strains. Variation in the number of tandem repeats in the coding sequence of Spy1336/R28 is responsible for size variation of R28 protein in natural populations. Isogenic mutant strains in which genes encoding R28 or transcriptional regulator Spy1337 are inactivated are significantly less virulent in a nonhuman primate model of necrotizing myositis. Our findings provide impetus for additional studies addressing the role of R28 and Spy1337 variation in pathogen-host interactions.

Group A streptococcal bacteremias in Southwest Finland 2007-2018: epidemiology and role of infectious diseases consultation in antibiotic treatment selection

The incidence of invasive group A streptococcal (GAS) infections has shown a fluctuating but increasing trend in Finland. The impact of infectious diseases specialist consultation (IDSC) on the antimicrobial therapy of GAS bacteremia has not been studied earlier. A retrospective study on adult GAS bacteremia in The Hospital District of Southwest Finland (HDSWF) was conducted from 2007 to 2018. Data on incidence of bacteremic GAS cases were gathered from the National Infectious Disease Register. Clinical data were obtained by reviewing the electronic patient records. The overall incidence of GAS bacteremia in HDSWF was 3.52/100,000, but year-to-year variation was observed with the highest incidence of 7.93/100,000 in 2018. A total of 212 adult GAS bacteremia cases were included. A record of IDSC was found (+) in 117 (55.2%) cases, not found (−) in 71 (33.5%) cases and data were not available in 24 (11.3%) cases. Among IDSC+ cases, 57.3% were on penicillin G treatment whereas in the group IDSC− only 22.5%, respectively (OR = 4.61, 95% CI 2.37–8.97; p < 0.001). The use of clindamycin as adjunctive antibiotic was more common among IDSC+ (54.7%) than IDSC− (21.7%) (OR = 4.51, 95% CI 2.29–8.87; p < 0.001). There was an increasing trend in incidence of GAS bacteremia during the study period. Narrow-spectrum beta-lactam antibiotics were chosen, and adjunctive clindamycin was more commonly used, if IDSC took place. This highlights the importance of availability of IDSC but calls for improved practice among infectious diseases specialists by avoiding combination therapy with clindamycin in non-severe invasive GAS infections.

New Pathogenesis Mechanisms and Translational Leads Identified by Multidimensional Analysis of Necrotizing Myositis in Primates

A fundamental goal of contemporary biomedical research is to understand the molecular basis of disease pathogenesis and exploit this information to develop targeted and more-effective therapies. Necrotizing myositis caused by the bacterial pathogen Streptococcus pyogenes is a devastating human infection with a high mortality rate and few successful therapeutic options. We used dual transcriptome sequencing (RNA-seq) to analyze the transcriptomes of S. pyogenes and host skeletal muscle recovered contemporaneously from infected nonhuman primates. The in vivo bacterial transcriptome was strikingly remodeled compared to organisms grown in vitro, with significant upregulation of genes contributing to virulence and altered regulation of metabolic genes. The transcriptome of muscle tissue from infected nonhuman primates (NHPs) differed significantly from that of mock-infected animals, due in part to substantial changes in genes contributing to inflammation and host defense processes. We discovered significant positive correlations between group A streptococcus (GAS) virulence factor transcripts and genes involved in the host immune response and inflammation. We also discovered significant correlations between the magnitude of bacterial virulence gene expression in vivo and pathogen fitness, as assessed by previously conducted genome-wide transposon-directed insertion site sequencing (TraDIS). By integrating the bacterial RNA-seq data with the fitness data generated by TraDIS, we discovered five new pathogen genes, namely, S. pyogenes 0281 (Spy0281 [dahA]), ihk-irr, slr, isp, and ciaH, that contribute to necrotizing myositis and confirmed these findings using isogenic deletion-mutant strains. Taken together, our study results provide rich new information about the molecular events occurring in severe invasive infection of primate skeletal muscle that has extensive translational research implications.IMPORTANCE Necrotizing myositis caused by Streptococcus pyogenes has high morbidity and mortality rates and relatively few successful therapeutic options. In addition, there is no licensed human S. pyogenes vaccine. To gain enhanced understanding of the molecular basis of this infection, we employed a multidimensional analysis strategy that included dual RNA-seq and other data derived from experimental infection of nonhuman primates. The data were used to target five streptococcal genes for pathogenesis research, resulting in the unambiguous demonstration that these genes contribute to pathogen-host molecular interactions in necrotizing infections. We exploited fitness data derived from a recently conducted genome-wide transposon mutagenesis study to discover significant correlation between the magnitude of bacterial virulence gene expression in vivo and pathogen fitness. Collectively, our findings have significant implications for translational research, potentially including vaccine efforts.

Beta-Hemolytic Streptococci and Necrotizing Soft Tissue Infections

β-hemolytic streptococci are major causes of necrotizing soft tissue infections (NSTIs), Streptococcus pyogenes (group A streptococcus; GAS) in particular. NSTIs caused by Streptococcus dysgalactiae (SD) have also been reported. In the INFECT cohort of 409 NSTIs patients, more than a third of the cases were caused by GAS (31%) or SD (7%). Risk factors of streptococcal NSTIs compared to streptococcal cellulitis have previously been largely unknown. The INFECT study confirmed blunt trauma as an important risk factor. In addition, absence of pre-existing skin lesions and a lower BMI were associated with NSTIs. The study also confirmed that septic shock is more frequent in GAS cases than in other types of NSTIs. Septic shock was also among several predictors of mortality. The role of intravenous immunoglobulin (IVIG) in streptococcal NSTIs has been unclear. In the INFECT cohort, IVIG treatment was associated with increased survival. As in other studies, a significant microbial diversity was observed, but with predominance of a few emm types. Overall, the INFECT study gives a comprehensive and contemporary picture of the clinical characteristics and the microbes involved in streptococcal NSTIs. The reported severity of disease underscores the need for new efforts aimed at identifying novel diagnostic measures and improved treatment.

Changes in emm types and superantigen gene content of Streptococcus pyogenes causing invasive infections in Portugal

Fluctuations in the clonal composition of Group A Streptococcus (GAS) have been associated with the emergence of successful lineages and with upsurges of invasive infections (iGAS). This study aimed at identifying changes in the clones causing iGAS in Portugal. Antimicrobial susceptibility testing, emm typing and superantigen (SAg) gene profiling were performed for 381 iGAS isolates from 2010-2015. Macrolide resistance decreased to 4%, accompanied by the disappearance of the M phenotype and an increase of the iMLS_B phenotype. The dominant emm types were: emm1 (28%), emm89 (11%), emm3 (9%), emm12 (8%), and emm6 (7%). There were no significant changes in the prevalence of individual emm types, emm clusters, or SAg profiles when comparing to 2006-2009, although an overall increasing trend was recorded during 2000-2015 for emm1, emm75, and emm87. Short-term increases in the prevalence of emm3, emm6, and emm75 may have been driven by concomitant SAg profile changes observed within these emm types, or reflect the emergence of novel genomic variants of the same emm types carrying different SAgs.

Molecular Characterization of Streptococcus pyogenes Causing Invasive Disease in Pediatric Population in Spain A 12-year Study

OBJECTIVES

To perform a comprehensive description of the epidemiology of Streptococcus pyogenes invasive disease in the pediatric population in 2 regions of Spain (Catalonia and Gipuzkoa) through 12 years.

METHODS

All S. pyogenes isolates causing invasive disease in pediatric patients between 2005 and 2016 were included. The emm-type and the presence of 13 exotoxin genes (speA, speB, speC, speF, speG, speH, speI, speJ, speK, speL, speM, smeZ, ssa and slo) were determined in all 93 available isolates and the Multi Locus Sequece Typing in 10% of isolates of each different emm-type.

RESULTS

Overall, 103 cases of S. pyogenes invasive infections were detected: 77 in Catalonia and 26 in Gipuzkoa, being 50.5% females. The incidence rate per 100,000 children was 2.5 for Gipuzkoa and 2.6 for Catalonia, with no significant temporal trends. The median age was 30 months. The most frequent clinical presentations were: pneumonia (26.2%), bacteremia/sepsis (23.3%), septic arthritis/osteomyelitis (22.3%), cellulitis/mastoiditis (12.6%) and meningitis (6.8%). Eight children developed streptococcal toxic shock syndrome. Nine cases were preceded by varicella infection. The associated mortality rate was 3.9%. Three isolates were resistant to erythromycin, being one of them also resistant to clindamycin and 4 isolates were resistant to levofloxacine. Forteen different emm-types were detected being emm1/ST28 (40.9%) the most frequent clone in both regions followed by emm12/ST36-ST242, emm6/ST382, emm3/ST15, emm75/ST150 and emm4/ST38-39. speA gene was only detected in emm1 and emm3 isolates. Eight exotoxins were enough to assign an emm-type with a very high degree of accuracy (95%). The 30-valent vaccine would include 96.8% of isolates.

Long-term, single-center surveillance of non-invasive group A streptococcal (GAS) infections, emm types and emm clusters

Group A streptococci (GAS) are among the most frequent pathogens in children. Many epidemiological studies focus on specific GAS infections (such as tonsillopharyngitis or invasive disease), on GAS carriers or on post-streptococcal sequelae. By comparison, reports on regional GAS characteristics, particularly circulating non-invasive GAS in Europe, are rare. In a monocentric study, all GAS isolated from pediatric patients at a tertiary care hospital over a 6-year period (2006-2012) were characterized. GAS emm types and clusters were determined. Associated patient data were analyzed. Five hundred sixty-six GAS strains were collected. GAS tonsillopharyngitis was most common (71.6%), followed by pyoderma (6.0%), otitis media (3.7%), perineal dermatitis (3.4%), and invasive infections (1.4%). Colonizing strains represented 13.6% of GAS. GAS emm12 was most prevalent among invasive and non-invasive isolates. Emm1, emm4, emm28, and emm89 were the most frequent non-invasive GAS strains. The emm E4 cluster was most common, followed by the A-C4, A-C3, and E1. Among the GAS infections, different emm types and clusters were identified, e.g., emm4 was more common among patients with scarlet fever. Three new emm subtypes were characterized: emm29.13, emm36.7, and emm75.5. This comprehensive review of a large, local GAS cohort points to the differences between and similarities among GAS genotypes and disease manifestations, while minimizing regional variations. Considerable deviation from previous epidemiological findings is described, especially regarding the frequent detection of emm1 and emm89 in non-invasive GAS infections. Periodic updates on molecular and epidemiological GAS characteristics are needed to track the multifaceted pathogenic potential of GAS.

Necrotizing Soft Tissue Infection: Diagnostic Accuracy of Physical Examination, Imaging, and LRINEC Score: A Systematic Review and Meta-Analysis

OBJECTIVE

We sought to summarize accuracy of physical examination, imaging, and Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score in diagnosis of necrotizing soft tissue infection (NSTI) in adults with a soft tissue infection clinically concerning for NSTI.

SUMMARY OF BACKGROUND DATA

NSTI is a life-threatening diagnosis. Delay to diagnosis and surgical management is associated with increased mortality.

METHODS

We searched 6 databases from inception through November 2017. We included English-language studies reporting diagnostic accuracy of testing or LRINEC Score. Outcome was NSTI confirmed by surgery or histopathology. Two reviewers screened all citations and extracted data independently. Summary measures were obtained from the Hierarchical Summary Receiver Operating Characteristic model.

RESULTS

From 2,290 citations, we included 23 studies (n = 5982). Of physical examination signs, pooled sensitivity and specificity for fever was 46.0% and 77.0% respectively, for hemorrhagic bullae 25.2% and 95.8%, and for hypotension 21.0% and 97.7%. Computed tomography (CT) had sensitivity of 88.5% and specificity of 93.3%, while plain radiography had sensitivity of 48.9% and specificity of 94.0%. Finally, LRINEC ≥ 6 had sensitivity of 68.2% and specificity of 84.8%, while LRINEC ≥ 8 had sensitivity of 40.8% and specificity of 94.9%.

CONCLUSIONS

Absence of any 1 physical examination feature (eg, fever or hypotension) is not sufficient to rule-out NSTI. CT is superior to plain radiography. LRINEC had poor sensitivity, and should not be used to rule-out NSTI. Given the poor sensitivity of these tests, a high clinical suspicion warrants early surgical consultation for definitive diagnosis and management.

Necrotizing skin and soft-tissue infections in the intensive care unit

BACKGROUND

Necrotizing skin and soft-tissue infections (NSTI) are rare but potentially life-threatening and disabling infections that often require intensive care unit admission.

OBJECTIVES

To review all aspects of care for a critically ill individual with NSTI.

SOURCES

Literature search using Medline and Cochrane library, multidisciplinary panel of experts.

CONTENT

The initial presentation of a patient with NSTI can be misleading, as features of severe systemic toxicity can obscure sometimes less impressive skin findings. The infection can spread rapidly, and delayed surgery worsens prognosis, hence there is a limited role for additional imaging in the critically ill patient. Also, the utility of clinical scores is contested. Prompt surgery with aggressive debridement of necrotic tissue is required for source control and allows for microbiological sampling. Also, prompt administration of broad-spectrum antimicrobial therapy is warranted, with the addition of clindamycin for its effect on toxin production, both in empirical therapy, and in targeted therapy for monomicrobial group A streptococcal and clostridial NSTI. The role of immunoglobulins and hyperbaric oxygen therapy remains controversial.

IMPLICATIONS

Close collaboration between intensive care, surgery, microbiology and infectious diseases, and centralization of care is fundamental in the approach to the severely ill patient with NSTI. As many aspects of management of these rare infections are supported by low-quality data only, multicentre trials are urgently needed.

Decoding the molecular epidemiology of group A streptococcus - an Indian perspective

PURPOSE

Unlike western countries the knowledge of group A streptococcus (GAS) epidemiology in India remains patchy and incomplete. Typing is crucial for surveillance as well as in predicting the efficacy of multivalent M protein vaccine. The present study aimed to explore the emm types of 206 invasive and non-invasive GAS isolates from South India as well as reviewing all the published literature on GAS molecular epidemiology from India thereby generating a pan-Indian data to predict the conjectural coverage of the 30-valent M-protein vaccine in this population.

METHODOLOGY

emm typing and superantigen (SAg) profiling of GAS along with reviewing literatures on GAS molecular epidemiology from India.

RESULTS

This study revealed a high diversity of emm types with emm 63, 82, 183, 85, 92, 169, 42, 44, 106, 74, 12 being frequently encountered, belonging to twenty emm clusters. The pan-Indian data on prevalent emm types further supports our study findings with 135 emm different types. Six clusters dominated accounting for 80 % of the GAS isolates: E3(26 %), E6(20 %), E2(11 %), E4(10 %), D4(7 %), E1(6 %). No significant association was noted between emm types and the nature of infection (P≥0.05) while a few SAg profiles were significantly associated with certain emm types. Pan Indian data revealed that only 16 % of the emm types encountered were included in proposed 30-valent M protein based vaccine.

CONCLUSION

The coverage among the South Indian GAS isolates was 28.2 % which increased to only 46.6 % with the cross-opsonic effect, thus highlighting the importance of developing a specific multivalent vaccine including the prevalent emm types in India or considering the use of conserved C-repeat vaccines and non-M protein based vaccines.

A multi-center clinical investigation on invasive Streptococcus pyogenes infection in China, 2010-2017

Background

Invasive S. pyogenes diseases are uncommon, serious infections with high case fatality rates (CFR). There are few publications on this subject in the field of pediatrics. This study aimed at characterizing clinical and laboratory aspects of this disease in Chinese children.

Patients and methods

A retrospective study was conducted and pediatric in-patients with S. pyogenes infection identified by cultures from normally sterile sites were included, who were diagnosed and treated in 9 tertiary hospitals during 2010–2017.

Results

A total of 66 cases were identified, in which 37 (56.1%) were male. The median age of these patients, including 11 neonates, was 3.0 y. Fifty-nine (89.4%) isolates were determined from blood. Fever was the major symptom (60/66, 90.9%) and sepsis was the most frequent presentation (64/66, 97.0%, including 42.4% with skin or soft tissue infections and 25.8% with pneumonia. The mean duration of the chief complaint was (3.8 ± 3.2) d. Only 18 (27.3%) patients had been given antibiotics prior to the hospitalization. Among all patients, 15 (22.7%) developed streptococcal toxin shock syndrome (STSS). No S. pyogenes strain was resistant to penicillin, ceftriaxone, or vancomycin, while 88.9% (56/63) and 81.4% (48/59) of the tested isolates were resistant to clindamycin and erythromycin respectively. Most of the patients were treated with β-lactams antibiotics and 36.4% had been treated with meropenem or imipenem. Thirteen (19.7%) cases died from infection, in which 9 (13.6%) had complication with STSS.

Conclusions

Invasive S. pyogenes infections often developed from skin or soft tissue infection and STSS was the main cause of death in Chinese children. Ongoing surveillance is required to gain a greater understanding of this disease.

Scarce evidence of efficacy of hyperbaric oxygen therapy in necrotizing soft tissue infection: a systematic review

Background: Necrotizing soft tissue infection (NSTI) is a rare and potentially life-threatening disease. Rapid surgical intervention, antibiotics and intensive care are the mainstay of treatment. Hyperbaric oxygen therapy (HBOT) is used as adjuvant therapy in some centres but there is a lack of research-based evidence of efficacy. Methods: Following the PRISMA guideline we conducted a systematic review on the efficacy of HBOT on NSTI with mortality as primary outcome. Through January 2019 major databases were searched and relevant literature assessed. The criteria for study inclusion were research of any design and any period of time comparing HBOT vs. non-HBOT in a population of NSTI-patients. Studies were analysed using the modified Delphi method and risk of bias in non-randomized studies - of interventions tool. Relative risk (RR) on mortality was calculated for each study individually. Results: A number of 1733 studies were identified through database search. Ultimately, 21 studies were included of which 19 were case series with a control group. The majority of the studies performed poor in quality assessment and all featured a high to critical risk of bias. The association of HBOT on mortality was generally reported as positive, however, the results should be considered with great scepticism. Conclusions: The evidence of HBOT in NSTI is poor and biased. There is a strong need for randomized controlled trials (RCTs) to shed light on a potential life-saving treatment.

Prospective Surveillance of Pediatric Invasive Group A Streptococcus Infection

BACKGROUND

Invasive group A Streptococcus (GAS) disease has an incidence in high-income countries of 3 to 5 per 100000 per annum and a case-fatality ratio of 10% to 15%. Although these rates are comparable to those of invasive meningococcal disease in Australia before vaccine introduction, invasive GAS disease currently requires reporting in only 2 jurisdictions.

METHODS

Data were collected prospectively through active surveillance at the Royal Children's Hospital, Melbourne (October 2014 to September 2016). Isolation of GAS from a sterile site was required for inclusion. Comprehensive demographic and clinical data were collected, and emm typing was performed on all isolates. Disease was considered severe if the patient required inotropic support or mechanical ventilation.

RESULTS

We recruited 28 patients. The median age of the patients was 3.5 years (range, 4 days to 11 years). Ten (36%) patients had severe disease. Fifteen (54%) children had presented to a medical practitioner for review in the 48 hours before their eventual admission, including 7 of the 10 patients with severe GAS infection. Complications 6 months after discharge persisted in 21% of the patients. emm1 was the most common emm type (29%).

CONCLUSION

We found considerable short- and longer-term morbidity associated with pediatric invasive GAS disease in our study. Disease manifestations were frequently severe, and more than one-third of the patients required cardiorespiratory support. More than one-half of the patients attended a medical practitioner for assessment but were discharged in the 48-hour period before admission, which suggests that there might have been a window for earlier diagnosis. Our methodology was easy to implement as a surveillance system.

SuPAR correlates with mortality and clinical severity in patients with necrotizing soft-tissue infections: results from a prospective, observational cohort study

Necrotizing soft tissue infections (NSTI) have a 90-day mortality rate of 18–22%. Tools are needed for estimating the prognosis and severity of NSTI upon admission. We evaluated soluble urokinase-type plasminogen activator receptor (suPAR) levels at admission as a prognostic marker of NSTI severity and mortality. In a prospective, observational cohort study, suPAR was measured in 200 NSTI patients. We compared admission suPAR levels in survivors and non-survivors, patients with septic shock and non-shock, amputation and non-amputation, correlations with Simplified Acute Physiology Score II (SAPS II) and the Sequential Organ Failure Assessment (SOFA) score. Admission suPAR levels were higher in septic shock vs. non-septic shock patients (9.2 vs. 5.8 ng/mL, p-value < 0.001) and non-survivors vs. survivors (11 vs. 6.1 ng/mL, p-value < 0.001) and correlated with SAPS II (r = 0.52, p < 0.001) and SOFA score (r = 0.64, p < 0.001). Elevated suPAR upon admission was associated with 90-day mortality (log-rank test p < 0.001), however not after adjustment for age, sex, and SOFA score. The AUC for suPAR and 90-day mortality was 0.77. We found that suPAR is a promising candidate for prognosis and severity in patients with NSTI.

Integrated analysis of population genomics, transcriptomics and virulence provides novel insights into Streptococcus pyogenes pathogenesis

Streptococcus pyogenes causes 700 million human infections annually worldwide, yet, despite a century of intensive effort, there is no licensed vaccine against this bacterium. Although a number of large-scale genomic studies of bacterial pathogens have been published, the relationships among the genome, transcriptome, and virulence in large bacterial populations remain poorly understood. We sequenced the genomes of 2,101 emm28 S. pyogenes invasive strains, from which we selected 492 phylogenetically diverse strains for transcriptome analysis and 50 strains for virulence assessment. Data integration provided a novel understanding of the virulence mechanisms of this model organism. Genome-wide association study, expression quantitative trait loci analysis, machine learning, and isogenic mutant strains identified and confirmed a one-nucleotide indel in an intergenic region that significantly alters global transcript profiles and ultimately virulence. The integrative strategy that we used is generally applicable to any microbe and may lead to new therapeutics for many human pathogens.

Gene fitness landscape of group A streptococcus during necrotizing myositis

Necrotizing fasciitis and myositis are devastating infections characterized by high mortality. Group A streptococcus (GAS) is a common cause of these infections, but the molecular pathogenesis is poorly understood. We report a genome-wide analysis using serotype M1 and M28 strains that identified GAS genes contributing to necrotizing myositis in nonhuman primates (NHP), a clinically relevant model. Using transposon-directed insertion-site sequencing (TraDIS), we identified 126 and 116 GAS genes required for infection by serotype M1 and M28 organisms, respectively. For both M1 and M28 strains, more than 25% of the GAS genes required for necrotizing myositis encode known or putative transporters. Thirteen GAS transporters contributed to both M1 and M28 strain fitness in NHP myositis, including putative importers for amino acids, carbohydrates, and vitamins and exporters for toxins, quorum-sensing peptides, and uncharacterized molecules. Targeted deletion of genes encoding 5 transporters confirmed that each isogenic mutant strain was significantly (P < 0.05) impaired in causing necrotizing myositis in NHPs. Quantitative reverse-transcriptase PCR (qRT-PCR) analysis showed that these 5 genes are expressed in infected NHP and human skeletal muscle. Certain substrate-binding lipoproteins of these transporters, such as Spy0271 and Spy1728, were previously documented to be surface exposed, suggesting that our findings have translational research implications.