Elucidation of independently modulated genes in Streptococcus pyogenes reveals carbon sources that control its expression of hemolytic toxins.

Streptococcus pyogenes can cause a wide variety of acute infections throughout the body of its human host. An underlying transcriptional regulatory network (TRN) is responsible for altering the physiological state of the bacterium to adapt to each unique host environment. Consequently, an in-depth understanding of the comprehensive dynamics of the S. pyogenes TRN could inform new therapeutic strategies. Here, we compiled 116 existing high-quality RNA sequencing data sets of invasive S. pyogenes serotype M1 and estimated the TRN structure in a top-down fashion by performing independent component analysis (ICA). The algorithm computed 42 independently modulated sets of genes (iModulons). Four iModulons contained the nga-ifs-slo virulence-related operon, which allowed us to identify carbon sources that control its expression. In particular, dextrin utilization upregulated the nga-ifs-slo operon by activation of two-component regulatory system CovRS-related iModulons, altering bacterial hemolytic activity compared to glucose or maltose utilization. Finally, we show that the iModulon-based TRN structure can be used to simplify the interpretation of noisy bacterial transcriptome data at the infection site. IMPORTANCE S. pyogenes is a pre-eminent human bacterial pathogen that causes a wide variety of acute infections throughout the body of its host. Understanding the comprehensive dynamics of its TRN could inform new therapeutic strategies. Since at least 43 S. pyogenes transcriptional regulators are known, it is often difficult to interpret transcriptomic data from regulon annotations. This study shows the novel ICA-based framework to elucidate the underlying regulatory structure of S. pyogenes allows us to interpret the transcriptome profile using data-driven regulons (iModulons). Additionally, the observations of the iModulon architecture lead us to identify the multiple regulatory inputs governing the expression of a virulence-related operon. The iModulons identified in this study serve as a powerful guidepost to further our understanding of S. pyogenes TRN structure and dynamics.

Streptococcus pyogenes upregulates arginine catabolism to exert its pathogenesis on the skin surface.

The arginine deiminase (ADI) pathway has been found in many kinds of bacteria and functions to supplement energy production and provide protection against acid stress. The Streptococcus pyogenes ADI pathway is upregulated upon exposure to various environmental stresses, including glucose starvation. However, there are several unclear points about the advantages to the organism for upregulating arginine catabolism. We show that the ADI pathway contributes to bacterial viability and pathogenesis under low-glucose conditions. S. pyogenes changes global gene expression, including upregulation of virulence genes, by catabolizing arginine. In a murine model of epicutaneous infection, S. pyogenes uses the ADI pathway to augment its pathogenicity by increasing the expression of virulence genes, including those encoding the exotoxins. We also find that arginine from stratum-corneum-derived filaggrin is a key substrate for the ADI pathway. In summary, arginine is a nutrient source that promotes the pathogenicity of S. pyogenes on the skin.

Genetic Characterization of Streptococcus pyogenes emm89 Strains Isolated in Japan From 2011 to 2019.

Invasive infection caused by Streptococcus pyogenes emm89 strains has been increasing in several countries linked to a recently emergent clade of emm89 strains, designated clade 3. In Japan, the features of emm89 S. pyogenes strains, such as clade classification, remains unknown. In this study, we collected emm89 strains isolated from both streptococcal toxic shock syndrome (STSS) (89 STSS isolates) and noninvasive infections (72 non-STSS isolates) in Japan from 2011 to 2019, and conducted whole-genome sequencing and comparative analysis, which resulted in classification of a large majority into clade 3 regardless of disease severity. In addition, invasive disease-associated factors were found among emm89 strains, including mutations of control of virulence sensor, and absence of the hylP1 gene encoding hyaluronidase. These findings provide new insights into genetic features of emm89 strains.

Streptococcus pyogenes Transcriptome Changes in the Inflammatory Environment of Necrotizing Fasciitis.

Streptococcus pyogenes is a major cause of necrotizing fasciitis, a life-threatening subcutaneous soft-tissue infection. At the host infection site, the local environment and interactions between the host and bacteria have effects on bacterial gene expression profiles, while the gene expression pattern of S. pyogenes related to this disease remains unknown. In this study, we used a mouse model of necrotizing fasciitis and performed RNA-sequencing (RNA-seq) analysis of S. pyogenes M1T1 strain 5448 by isolating total RNA from infected hind limbs obtained at 24, 48, and 96 h postinfection. RNA-seq analysis results identified 483 bacterial genes whose expression was consistently altered in the infected hindlimbs compared to their expression under in vitro conditions. Genes showing consistent enrichment during infection included 306 encoding molecules involved in virulence, carbohydrate utilization, amino acid metabolism, trace-metal transport, and the vacuolar ATPase transport system. Surprisingly, drastic upregulation of 3 genes, encoding streptolysin S precursor (sagA), cysteine protease (speB), and secreted DNase (spd), was noted in the present mouse model (log2 fold change, >6.0, >9.4, and >7.1, respectively). Conversely, the number of consistently downregulated genes was 177, including those associated with the oxidative stress response and cell division. These results suggest that in necrotizing fasciitis, S. pyogenes shows an altered metabolism, decreased cell proliferation, and upregulation of expression of major toxins. Our findings are considered to provide critical information for developing novel treatment strategies and vaccines for necrotizing fasciitis.IMPORTANCE Necrotizing fasciitis, a life-threatening subcutaneous soft-tissue infection, is principally caused by S. pyogenes The inflammatory environment at the site of infection causes global gene expression changes for survival of the bacterium and pathogenesis. However, no known study regarding transcriptomic profiling of S. pyogenes in cases of necrotizing fasciitis has been presented. We identified 483 bacterial genes whose expression was consistently altered during infection. Our results showed that S. pyogenes infection induces drastic upregulation of the expression of virulence-associated genes and shifts metabolic pathway usage. In particular, high-level expression of toxins, such as cytolysins, proteases, and nucleases, was observed at infection sites. In addition, genes identified as consistently enriched included those related to metabolism of arginine and histidine as well as carbohydrate uptake and utilization. Conversely, genes associated with the oxidative stress response and cell division were consistently downregulated during infection. The present findings provide useful information for establishing novel treatment strategies.

[Bentall Procedure and Total Arch Replacement with an Open Stentgraft after Ascending Aortic Replacement for Acute Type A Aortic Dissection].

A 40-year-old man underwent ascending aortic replacement for acute type A aortic dissection. Eight years later, Bentall procedure and total arch replacement with an open stentgraft (OSG) were performed due to enlargement of the aortic root and distal arch dissection as well as exacerbation of aortic valve incompetence. The computed tomography(CT) taken at 22 months postoperatively showed better stentgraft expansion than that immediately after the operation, reduction in the diameter of the distal aortic arch, and thrombosis of the false lumen from the aortic arch to the entire descending aorta. However, the CT taken at 33 months postoperatively revealed a new entry to the distal end of the stentgraft and blood flow in the false lumen. Although OSG is useful for extensive aortic aneurysm, strict follow-up is necessary in OSG for aortic dissection.

[Mitral valve replacement for cabergoline-related severe mitral regurgitation].

An 82-year-old man was referred to our hospital because of progressive heart failure. He had Parkinson's disease and had been treated with cabergoline during the preceding 4 years and 8 months. Echocardiography revealed severe mitral regurgitation through retracted mitral leaflets with incomplete coaptation. Heart failure persisted despite pharmacologic therapy, so the mitral valve was surgically replaced with a biological valve. Histologic analysis showed fibrous thickened mitral chordae with myxoid degeneration. These characteristics of the mitral valve of our patient are similar to the valvular heart disease described with the use of cabergoline. Clinicians must be care of valvular heart disease whenever they treat Parkinson's disease patients with cabergoline.

Papillary muscle rupture following acute myocardial infarction.

OBJECTIVES: Papillary muscle rupture following acute myocardial infarction (AMI), which rarely occurs, leads to catastrophic outcomes. We reviewed 6 patients who were diagnosed as having papillary muscle rupture. SUBJECTS AND METHODS: Between February 1986 and September 2002, 6 consecutive patients underwent mitral valve replacement (MVR) for acute mitral regurgitation due to postinfarction papillary muscle rupture (4 men and 2 women, mean age 67 years). Preoperatively, all were in New York Heart Association (NYHA) class IV. All patients had intraaortic balloon pumping, and one needed additional percutaneous cardiopulmonary support. Operations were performed within 1 to 19 days (mean 6.8) after the onset of AMI, and within 24 hours after papillary muscle rupture. Complete ruptures were found in 5 of 6 patients. Four patients had posterior papillary rupture and 2 patients anterior. All patients underwent MVR to preserve the posterior mitral leaflet. Concomitant coronary artery bypass grafting was performed in 5 of 6 patients (mean 1.6 grafts per person) and pulmonary venous isolation for atrial fibrillation in one patient. RESULTS: The cardiopulmonary bypass time ranged from 178 to 325 minutes (mean 236), and the aortic cross clamp time from 123 to 196 minutes (mean 155). Two patients died of low cardiac output syndrome. Of 4 operative survivors, 3 patients were in NYHA class I and one in class II. The mean follow-up term was 21 months. One patient with the pulmonary venous isolation has been in sinus rhythm. All survivors have been doing well without any valve related complications. CONCLUSION: Six patients underwent MVR for the papillary muscle rupture following AMI and the perioperative mortality rate was 33%. All survivors have been well with no cardiac events. We propose that in papillary muscle rupture following AMI emergent surgery should be undertaken as soon as possible, and that concomitant surgery should be performed as thoroughly as possible.