AMPK/Drp1 pathway mediates Streptococcus uberis-Induced mitochondrial dysfunction.

Excessive production of reactive oxygen species (ROS) leads to oxidative stress in host cells and affects the progress of disease. Mitochondria are an important source of ROS and their dysfunction is closely related to ROS production. S. uberis is a common causative agent of mastitis. The expression of key enzymes of the mitochondrial apoptotic pathway is increased in mammary epithelial cells after S. uberis stimulation, while expression of proteins related to mitochondrial function is decreased. Drp1, a key protein associated with mitochondrial function, is activated upon infection. Accompanied by mitochondria-cytosol translocation of Drp1, Fis1 expression is significantly upregulated while Mfn1 expression is downregulated implying that the balance of mitochondrial dynamics is disrupted. This leads to mitochondrial fragmentation, decreased mitochondrial membrane potential, higher levels of mROS and oxidative injury. The AMPK activator AICAR inhibits the increased phosphorylation of Drp1 and the translocation of Drp1 to mitochondria by salvaging mitochondrial function in an AMPK/Drp1 dependent manner, which has a similar effect to Drp1 inhibitor Mdivi-1. These data show that AMPK, as an upstream negative regulator of Drp1, ameliorates mitochondrial dysfunction induced by S. uberis infection.

Genome-Wide CRISPR-Cas9 Screen Does Not Identify Host Factors Modulating Streptococcus agalactiae ß-Hemolysin/Cytolysin-Induced Cell Death.

Pore-forming toxins (PFTs) are commonly produced by pathogenic bacteria, and understanding them is key to the development of virulence-targeted therapies. Streptococcus agalactiae, or group B Streptococcus (GBS), produces several factors that enhance its pathogenicity, including the PFT ß-hemolysin/cytolysin (ßhc). Little is understood about the cellular factors involved in ßhc pore formation. We conducted a whole-genome CRISPR-Cas9 forward genetic screen to identify host genes that might contribute to ßhc pore formation and cell death. While the screen identified the established receptor, CD59, in control experiments using the toxin intermedilysin (ILY), no clear candidate genes were identified that were required for ßhc-mediated lethality. Of the top targets from the screen, two genes involved in membrane remodeling and repair represented candidates that might modulate the kinetics of ßhc-induced cell death. Upon attempted validation of the results using monoclonal cell lines with targeted disruption of these genes, no effect on ßhc-mediated cell lysis was observed. The CRISPR-Cas9 screen results are consistent with the hypothesis that ßhc does not require a single nonessential host factor to mediate target cell death. IMPORTANCE CRISPR-Cas9 forward genetic screens have been used to identify host cell targets required by bacterial toxins. They have been used successfully to both verify known targets and elucidate novel host factors required by toxins. Here, we show that this approach fails to identify host factors required for cell death due to ßhc, a toxin required for GBS virulence. These data suggest that ßhc may not require a host cell receptor for toxin function or may require a host receptor that is an essential gene and would not be identified using this screening strategy.

CLINICAL CHARACTERISTICS AND VISUAL OUTCOMES IN ENDOPHTHALMITIS AFTER KERATOPROSTHESIS IMPLANTATION.

PURPOSE: To describe the presentation, microbiology, management, and prognosis of eyes with endophthalmitis after Boston keratoprosthesis implantation. METHODS: Retrospective case series with history, diagnostics, management, and outcomes data in endophthalmitis after keratoprosthesis implantation presenting to a tertiary center between 2009 and 2020. RESULTS: Of 137 keratoprosthesis-implanted eyes, 7 eyes of 7 patients (5%) developed endophthalmitis. On presentation, 6 (86%) reported decreased visual acuity, and only 1 (14%) reported pain. Peripheral corneal ulcers were present in 2 eyes (29%). Seidel testing was negative in all cases. Six eyes (86%) had retroprosthetic membranes. One (14%) underwent initial pars plana vitrectomy with mechanical vitreous biopsy, whereas 6 (86%) received a needle vitreous tap-half of which were dry. Organisms were isolated after vitreous tap in two eyes: Streptococcus intermedius and Mycobacterium abscessus. The mean visual acuity preendophthalmitis, at presentation, and at 6 months were 20/267, 20/5,944, and 20/734, respectively. The visual acuity improved 9.08 ± 11.78 Early Treatment Diabetic Retinopathy Study lines from presentation to 6 months. Six-month visual acuity was correlated with preendophthalmitis visual acuity (r = 0.92, P = 0.003) but not presenting visual acuity (P = 0.838). CONCLUSION: Visual acuity at 6 months is correlated with preendophthalmitis visual acuity, not presenting visual acuity. Endophthalmitis should be considered in the differential diagnosis of painless intraocular inflammation any time after keratoprosthesis implantation, even if Seidel negative.

Infective Endocarditis-Associated Purpura and Glomerulonephritis Mimicking IgA Vasculitis: A Diagnostic Pitfall.

BACKGROUND: Purpura and glomerulonephritis are typical presentations in IgA vasculitis. Infective endocarditis mimicking IgA vasculitis by presenting with glomerulonephritis and purpura is rarely reported. METHODS: We searched for cases with infective endocarditis-associated purpura and glomerulonephritis in a tertiary hospital in China and retrospectively reviewed their clinicopathological features. Differential diagnosis and treatment in patients with infective endocarditis-associated purpura and glomerulonephritis were discussed. RESULTS: A total of 20 cases with infective endocarditis-associated purpura and glomerulonephritis were identified among 548 cases with infective endocarditis in our center during an 8-year period: 7 of the 20 cases (35%) were initially misdiagnosed as IgA vasculitis and 10 cases (50%) presented with left-sided endocarditis caused by Streptococcus viridans. Fever (100%, 20 out of 20), prior valvular deformities (80%, 16 out of 20), cardiac murmur (95%, 19 out of 20), splenomegaly (84%, 16 out of 19), embolism (55%, 11 out of 20), and hypocomplementemia (76%, 13 out of 17) were present in most patients. Crescents and mesangial hypercellularity with or without endothelial hypercellularity were the primary findings on light microscopy, with C3-dominant deposition on immunofluorescence. But IgA-dominant staining was also observed (40%, 2 out of 5). In patients with rapidly progressive glomerulonephritis, patients with complete recovery of renal function had shorter disease duration and higher ratio (67% vs 20%) of immunosuppressive therapy compared with patients with partial recovery. CONCLUSIONS: Infective endocarditis-associated glomerulonephritis and purpura can closely mimic IgA vasculitis. Differential diagnosis is challenging, particularly when typical presentations of infective endocarditis are absent. In adults with presentations like IgA vasculitis, infective endocarditis should be evaluated through comprehensive clinical and pathological investigations. Immunosuppressive therapy can be considered in patients with severe glomerulonephritis who do not improve after proper anti-infective therapy.

Streptococcal infection in childhood Henoch-Schönlein purpura: a 5-year retrospective study from a single tertiary medical center in China, 2015-2019.

BACKGROUND: The present study focuses on the associations of streptococcal infection with the clinical phenotypes, relapse/recurrence and renal involvement in Henoch-Schönlein purpura (HSP) children. METHODS: Two thousand seventy-four Chinese children with HSP were recruited from January 2015 to December 2019. Patients' histories associated with HSP onset were obtained by interviews and questionnaires. Laboratory data of urine tests, blood sample and infectious agents were collected. Renal biopsy was performed by the percutaneous technique. RESULTS: (1) Streptococcal infection was identified in 393 (18.9%) HSP patients, and served as the most frequent infectious trigger. (2) Among the 393 cases with streptococcal infection, 43.0% of them had arthritis/arthralgia, 32.1% had abdominal pain and 29.3% had renal involvement. (3) 26.1% of HSP patients relapsed or recurred more than 1 time within a 5-year observational period, and the relapse/recurrence rate in streptococcal infectious group was subjected to a 0.4-fold decrease as compared with the non-infectious group. (4) No significant differences in renal pathological damage were identified among the streptococcal infectious group, the other infectious group and the non-infectious group. CONCLUSIONS: Streptococcal infection is the most frequent trigger for childhood HSP and does not aggravate renal pathological damage; the possible elimination of streptococcal infection helps relieve the relapse/recurrence of HSP.

In vivo oxygen measurement in cerebrospinal fluid of pigs to determine physiologic and pathophysiologic oxygen values during CNS infections.

During infection and inflammation, a reduced oxygen level clearly affects cellular functions. Oxygen levels during CNS infections are unknown. Here we established and evaluated an in vivo measurement system to characterize the oxygen level in parallel with bacterial numbers (CFU/mL), the cell number and pH level inside the CSF of healthy compared to Streptococcus suis-infected pigs. The animals were anesthetized over a seven-hour period with isoflurane in air/oxygen at physiologic arterial partial pressure of oxygen. Oxygen levels in CSF of anesthetized pigs were compared to euthanized pigs. The detected partial pressure of oxygen in the CSF remained constant in a range of 47-63 mmHg, independent of the infection status (bacterial or cell number). In contrast, the pH value showed a slight drop during infection, which correlated with cell and bacterial number in CSF. We present physiologic oxygen and pH values in CSF during the onset of bacterial meningitis.

A 70-Year-Old Man With Conspicuous Thigh Pain and ST-Segment Elevations.

CASE PRESENTATION: A 70-year-old man presented to the ED with sudden onset of left thigh pain followed by transient chest discomfort. His history included cerebrovascular disease, hypertension, and cocaine and methamphetamine use. Physical examination revealed an uncomfortable male subject with a temperature of 37 °C, heart rate of 129 beats/min, BP of 130/65 mm Hg, and 98% oxygen saturation on room air. There was point tenderness in the left lateral thigh without erythema, swelling, or overlying skin changes. His cardiac examination revealed an irregular tachycardia at 129 beats/min and normal first and second heart sounds without murmurs, gallops, or rubs. The remainder of the examination was unremarkable.

Clinical significance of Epstein-Barr virus in the cerebrospinal fluid of immunocompetent patients.

INTRODUCTION: Polymerase chain reaction (PCR)-based testing of cerebrospinal fluid (CSF) samples has greatly facilitated the diagnosis of central nervous system (CNS) infections. However, the clinical significance of Epstein-Barr virus (EBV) DNA in CSF of individuals with suspected CNS infection remains unclear. We wanted to gain a better understanding of EBV as an infectious agent in immunocompetent patients with CNS disorders. METHODS: We identified cases of EBV-associated CNS infections and reviewed their clinical and laboratory characteristics. The study population was drawn from patients with EBV PCR positivity in CSF who visited Pusan National University Hospital between 2010 and 2019. RESULTS: Of the 780 CSF samples examined during the 10-year study period, 42 (5.4 %) were positive for EBV DNA; 9 of the patients (21.4 %) were diagnosed with non-CNS infectious diseases, such as optic neuritis, Guillain-Barré syndrome, and idiopathic intracranial hypotension, and the other 33 cases were classified as CNS infections (22 as encephalitis and 11 as meningitis). Intensive care unit admission (13/33 patients, 39.3 %) and presence of severe neurological sequelae at discharge (8/33 patients, 24.2 %) were relatively frequent. In 10 patients (30.3 %), the following pathogens were detected in CSF in addition to EBV: varicella-zoster virus (n = 3), cytomegalovirus (n = 2), herpes simplex virus 1 (n = 1), herpes simplex virus 2 (n = 1), Streptococcus pneumomiae (n = 2), and Enterococcus faecalis (n = 1). The EBV-only group (n = 23) and the co-infection group (n = 10) did not differ in age, gender, laboratory data, results of brain imaging studies, clinical manifestations, or prognosis; however, the co-infected patients had higher CSF protein levels. CONCLUSION: EBV DNA in CSF is occasionally found in the immunocompetent population; the virus was commonly associated with encephalitis and poor prognosis, and frequently found together with other microbes in CSF.

Pathogen effects on milk yield and composition in chronic subclinical mastitis in dairy cows.

This study aimed to evaluate the effects of chronic subclinical mastitis (CSM) on milk production and component yields in dairy cows. A total of six herds located in the Midwest area of São Paulo State, Brazil were selected. Herds were visited once every 2 weeks to measure milk yield and to collect milk samples from lactating Holstein cows. Milk samples were collected at two stages (1 and 2), and each stage comprised three milk samplings. In stage 1, a total of 117 of 647 cows were diagnosed with CSM based on at least two of three repeated somatic cell counts (SCC) > 2000,000 cells/mL and positive bacterial milk culture results (BC). Cows with CSM were selected for the second stage. In stage 2, selected cows had quarter sampling aseptically collected for BC analyses prior to milking, and quarter milk yield was measured. Milk components (total protein, fat, lactose, and total solids) were measured using mid-infrared spectroscopy. Mammary quarters were considered healthy if all three repeated SCC results were ≤ 200,000 cells/mL and no bacterial growth was detected on BC. All quarters with positive bacterial growth were classified as having (non-chronic) subclinical mastitis when only one of three SCC results were > 200,000 cells/mL, and CSM when at least two of three SCC results were > 200,000 cells/mL. The effects of CSM by type of pathogen on milk and components yield were assessed using a linear mixed model. Mammary quarters with CSM caused by major pathogens had milk loss of 1.1 kg/quarter milking in comparison to healthy quarters. Milk losses were 0.8 and 1.3 kg/quarter milking when CSM was caused by Staphylococcus aureus or environmental streptococci, respectively. In addition, healthy quarters produced more milk components than quarters with CSM caused by major pathogens. Minor pathogens causing CSM (non-aureus staphylococci and Corynebacterium spp.) had no effect on milk yield. Quarters with CSM had lower milk and component yields when compared with healthy quarters. Milk losses varied according to the type of pathogen and were higher when associated with major pathogens such as S. aureus and environmental streptococci compared with healthy quarters.

CE: PANDAS: Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infection.

If undiagnosed and untreated, pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection (PANDAS) can suddenly and drastically disrupt the lives of previously healthy children and their families. The key to prompt diagnosis of PANDAS and its appropriate treatment is provider awareness that streptococcal infection may present with neuropsychiatric symptoms. The authors discuss the signs and symptoms that characterize PANDAS, as well as its presumed pathogenesis, and illustrate, through a composite case history, a symptom presentation, diagnostic journey, treatment course, and recovery that is representative of many PANDAS cases.

Integrin α5ß1, as a Receptor of Fibronectin, Binds the FbaA Protein of Group A Streptococcus To Initiate Autophagy during Infection.

Group A Streptococcus (GAS), one of the most common extracellular pathogens, has been reported to invade epithelial and endothelial cells. Our results reveal that M1 GAS strain SF370 can be effectively eliminated by respiratory epithelial cells. Emerging evidence indicates that autophagy is an important strategy for nonphagocytes to eliminate intracellular bacteria. Upon pathogen recognition, cell surface receptors can directly trigger autophagy, which is a critical step in controlling infection. However, the mechanisms of how cells sense invading bacteria and use this information specifically to trigger autophagy remain unclear. In this study, we stimulated cells and infected mice with M and FbaA mutants of M1 GAS strain SF370 or with purified M and FbaA proteins (two critical surface structural proteins of GAS), and found that only FbaA protein was involved in autophagy induction. Furthermore, the FbaA protein induced autophagy independent of common pattern recognition receptors (such as Toll-like receptors); rather, it relies on binding to integrin α5ß1 expressed on the cell surface, which is mediated by extracellular matrix protein fibronectin (Fn). The FbaA-Fn-integrin α5ß1 complex activates Beclin-1 through the mTOR-ULK1-Beclin-1 pathway, which enables the Beclin-1/Vps34 complex to recruit Rab7 and, ultimately, to promote the formation of autophagosomes. By knocking down integrin α5ß1, Fn, Atg5, Beclin-1, and ULK1 in Hep2 cells and deleting Atg5 or integrin α5ß1 in mice, we reveal a novel role for integrin α5ß1 in inducing autophagy. Our study demonstrates that integrin α5ß1, through interacting with pathogen components, initiates effective host innate immunity against invading intracellular pathogens.IMPORTANCE Autophagy is generally considered a strategy used by the innate immune system to eliminate invasive pathogens through capturing and transferring them to lysosomes. Currently, researchers pay more attention to how virulence factors secreted by GAS regulate the autophagic process. Here, we provide the first evidence that the structural protein FbaA of M1 GAS strain SF370 is a potent inducer of autophagy in epithelial cells. Furthermore, we demonstrate that integrin α5ß1 in epithelial cells in vitro and in vivo acts as a receptor to initiate the signaling for inducing autophagy by binding to FbaA of M1 GAS strain SF370 via Fn. Our study reveals the underlying mechanisms by which pathogens induce Fn-integrin α5ß1 to trigger autophagy in a conserved pattern in epithelial cells.

Periprosthetic joint infection with streptococcus dysgalactiae subspecies equisimilis: Case report.

Streptococcus dysgalactiae (SD) is a common pathogen among elderly population. However, to our knowledge, there is no periprosthetic joint infection case reported that is infected with Streptococcus dysgalactiae subspecies equisimilis (SDSE) in the English literature. In this article, we report a 77-year-old male patient who had undergone total knee arthroplasty three years ago and had the diagnosis of cellulitis at his leg followed by swelling, pain and hyperemia localized at his knee. Three knee aspirations were performed and the SDSE was identified. There was no direct contact of patient to animals.

Disseminated septic arthritis caused by Streptococcus equi infection.

We describe a rare case of bloodstream infection and disseminated septic arthritis in a relatively fit and well 73-year-old retired farmer and gamekeeper, due to the zoonotic organism Streptococcus equi The presence of the organism in multiple joints led to slow clinical response to treatment and was complicated by relapse of infection and lengthy disability. Source control was achieved with multiple joint washouts and spinal cord decompression. Following this, a 6-week course of intravenous antibiotics was required for complete clearance of infection. After a long period of rehabilitation, the patient made a good recovery. This case demonstrates that S. equi can cause life threatening and difficult to treat sepsis in humans and requires a high index of suspicion in people who have regular contact with equine species, cattle and unpasteurised milk.

Invasive Group A streptococcal postpartum endometritis associated with multi-organ infarctions: an uncommon case presentation and literature review.

Background: Streptococcal Toxic Shock Syndrome (STSS) is a serious condition that can arise from streptococcal postpartum endometritis. It is associated with a substantial increase in mortality rate and can rarely result in multiorgan infarction. Early recognition plays a vital role in patients' outcome. Objective: To report a case of complicated STSS and review the literature for previous case reports of streptococcal postpartum endometritis to determine if STSS diagnostic criteria (published by the Centers for Disease Control and Prevention) were fulfilled. Case presentation: This is a 41-year-old woman who presented 5 days after an uncomplicated vaginal delivery with endometritis complicated by invasive group A ß-hemolytic streptococcus (GAS) infection and confirmed toxic shock syndrome. The patient was initially admitted to the critical care unit due to hemodynamic compromise requiring intravenous (IV) fluids, IV antibiotic therapy with penicillin and clindamycin, and IV immunoglobulin therapy. The patient subsequently developed multi-organ infarctions, acute respiratory distress syndrome requiring noninvasive respiratory support, and severe reactive arthritis. Literature review revealed 15 case reports of GAS postpartum endometritis, five met criteria for confirmed STSS. One patient died from severe septic shock leading to cardiopulmonary arrest. Thirteen out of 15 cases of postpartum endometritis occurred after uncomplicated vaginal delivery. Conclusion: STSS is a serious and possibly fatal medical condition that requires early diagnosis and treatment to prevent poor patient outcomes and death. Careful consideration to the patient's postpartum clinical presentation with the implementation of an intradisciplinary approach should be utilized.

Host Pathways of Hemostasis that Regulate Group A Streptococcus pyogenes Pathogenicity.

A hallmark feature of severe Group A Streptococcus pyogenes (GAS) infection is dysregulated hemostasis. Hemostasis is the primary pathway for regulating blood flow through events that contribute towards clot formation and its dissolution. However, a number of studies have identified components of hemostasis in regulating survival and dissemination of GAS. Several proteins have been identified on the surface of GAS and they serve to either facilitate invasion to host distal sites or regulate inflammatory responses to the pathogen. GAS M-protein, a surface-exposed virulence factor, appears to be a major target for interactions with host hemostasis proteins. These interactions mediate biochemical events both on the surface of GAS and in the solution when M-protein is released into the surrounding environment through shedding or regulated proteolytic processes that dictate the fate of this pathogen. A thorough understanding of the mechanisms associated with these interactions could lead to novel approaches for altering the course of GAS pathogenicity.

Necrotizing Soft Tissue Infections: A Focused Review of Pathophysiology, Diagnosis, Operative Management, Antimicrobial Therapy, and Pediatrics.

Background: Necrotizing fasciitis is a major health problem throughout the world. The purpose of this review is to assist providers with the care of these patients through a better understanding of the pathophysiology and management options. Methods: This is a collaborative review of the literature between members of the Surgical Infection Society of North America and World Society of Emergency Surgery. Results: Necrotizing fasciitis continues to be difficult to manage with the mainstay being early diagnosis and surgical intervention. Recognition of at-risk populations assists with the initiation of treatment, thereby impacting outcomes. Conclusions: Although there are some additional treatment strategies available, surgical debridement and antimicrobial therapy are central to the successful eradication of the disease process.