Single-Cell Transcriptomic Analysis of Epstein-Barr Virus-Associated Hemophagocytic Lymphohistiocytosis.

Epstein-Barr virus (EBV) infection can lead to infectious mononucleosis (EBV-IM) and, more rarely, EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), which is characterized by a life-threatening hyperinflammatory cytokine storm with immune dysregulation. Interferon-gamma (IFNγ) has been identified as a critical mediator for primary HLH; however, the detailed role of IFNγ and other cytokines in EBV-HLH is not fully understood. In this study, we used single-cell RNA sequencing to characterize the immune landscape of EBV-HLH and compared it with EBV-IM. Three pediatric patients with EBV-HLH with different backgrounds, one with X-linked lymphoproliferative syndrome type 1 (XLP1), two with chronic active EBV disease (CAEBV), and two patients with EBV-IM were enrolled. The TUBA1B + STMN1 + CD8 + T cell cluster, a responsive proliferating cluster with rich mRNA detection, was explicitly observed in EBV-IM, and the upregulation of SH2D1A-the gene responsible for XLP1-was localized in this cluster. This proliferative cluster was scarcely observed in EBV-HLH cases. In EBV-HLH cases with CAEBV, upregulation of LAG3 was observed in EBV-infected cells, which may be associated with an impaired response by CD8 + T cells. Additionally, genes involved in type I interferon (IFN) signaling were commonly upregulated in each cell fraction of EBV-HLH, and activation of type II IFN signaling was observed in CD4 + T cells, natural killer cells, and monocytes but not in CD8 + T cells in EBV-HLH. In conclusion, impaired responsive proliferation of CD8 + T cells and upregulation of type I IFN signaling were commonly observed in EBV-HLH cases, regardless of the patients' background, indicating the key features of EBV-HLH.

MicroRNA expression profiling of urine exosomes in children with congenital cytomegalovirus infection.

Congenital cytomegalovirus (cCMV) infection can damage the central nervous system in infants; however, its prognosis cannot be predicted from clinical evaluations at the time of birth. Urinary exosomes can be used to analyze neuronal damage in neuronal diseases. To investigate the extent of neuronal damage in patients with cCMV, exosomal miRNA expression in the urine was investigated in cCMV-infected infants and controls. Microarray analysis of miRNA was performed in a cohort of 30 infants, including 11 symptomatic cCMV (ScCMV), 7 asymptomatic cCMV (AScCMV), and one late-onset ScCMV cases, and 11 healthy controls (HC). Hierarchical clustering analysis revealed the distinct expression profile of ScCMV. The patient with late-onset ScCMV was grouped into the ScCMV cluster. Pathway enrichment analysis of the target mRNAs differed significantly between the ScCMV and HC groups; this analysis also revealed that pathways related to brain development were linked to upregulated pathways. Six miRNAs that significantly different between groups (ScCMV vs. HC and ScCMV vs. AScCMV) were selected for digital PCR in another cohort for further validation. Although these six miRNAs seemed insufficient for predicting ScCMV, expression profiles of urine exosomal miRNAs can reveal neurological damage in patients with ScCMV compared to those with AcCMV or healthy infants.

Nanopore sequencing in distinguishing between wild-type and vaccine strains of Varicella-Zoster virus.

BACKGROUND: The introduction of varicella vaccines into routine pediatric immunization programs has led to a considerable reduction in varicella incidence. However, there have been reports of varicella, herpes zoster, and meningitis caused by the vaccine strain of varicella-zoster virus (VZV), raising concerns. Establishing the relationship between the wild-type and vaccine strains in VZV infections among previously vaccinated individuals is crucial. Differences in the single nucleotide polymorphisms (SNPs) among vaccine strains can be utilized to identify the strain. In this study, we employed nanopore sequencing to identify VZV strains and analyzed clinical samples. METHODS: We retrospectively examined vesicle and cerebrospinal fluid samples from patients with VZV infections. One sample each of the wild-type and vaccine strains, previously identified using allelic discrimination real-time PCR and direct sequencing, served as controls. Ten samples with undetermined VZV strains were included. After DNA extraction, a long PCR targeting the VZV ORF62 region was executed. Nanopore sequencing identified SNPs, allowing discrimination between the vaccine and wild-type strains. RESULTS: Nanopore sequencing confirmed SNPs at previously reported sites (105,705, 106,262, 107,136, and 107,252), aiding in distinguishing between wild-type and vaccine strains. Among the ten unknown samples, nine were characterized as wild strains and one as a vaccine strain. Even in samples with low VZV DNA levels, nanopore sequencing was effective in strain identification. CONCLUSION: This study validates that nanopore sequencing is a reliable method for differentiating between the wild-type and vaccine strains of VZV. Its ability to produce long-read sequences is remarkable, allowing simultaneous confirmation of known SNPs and the detection of new mutations. Nanopore sequencing can serve as a valuable tool for the swift and precise identification of wild-type and vaccine strains and has potential applications in future VZV surveillance.

Comparison of plasma proteomic profiles of patients with Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis and infectious mononucleosis.

Primary Epstein-Barr virus (EBV) infection occasionally causes EBV-infectious mononucleosis (EBV-IM) and EBV-hemophagocytic lymphohistiocytosis (EBV-HLH). Although EBV-IM is mostly mild and self-limiting, EBV-HLH is a life-threatening disease characterized by excessive immune activation. However, the pathogenesis of EBV-HLH is yet to be fully elucidated. A diagnostic biomarker for EBV-HLH is desirable because early diagnosis and treatment are critical for the effective management of patients. In this study, the proteomic profiling of plasma was performed using liquid chromatography-mass spectrometry to identify proteins specific to EBV-IM and EBV-HLH. Furthermore, pathway analysis was performed for the proteins upregulated in patients with EBV-IM and EBV-HLH. Compared to healthy controls, 63 and 18 proteins were upregulated in patients with EBV-IM and EBV-HLH, respectively. Pathway and process enrichment analyses revealed that the complement system was the most enriched category of upregulated proteins in EBV-IM, whereas proteins related to immune effector processes were the most enriched in EBV-HLH. Among the 18 proteins upregulated in EBV-HLH, seven were exclusive to EBV-HLH. These specific proteins were associated with three pathways, and apolipoprotein E was commonly found in all the pathways. Proteomic analysis may provide new insights into the host response to EBV infection and the pathogenesis of EBV-related diseases.

Proteomic Analysis Reveals Novel Plasma Biomarkers for Neurological Complications in Patients With Congenital Cytomegalovirus Infection.

BACKGROUND: Congenital cytomegalovirus (cCMV) infection is a leading cause of nonhereditary neurological complications. When considering antiviral treatment, it is important to differentiate between symptomatic and asymptomatic patients. This study aimed to identify candidate plasma biomarkers for neurological complications of cCMV infection using proteomic analysis. METHODS: This study retrospectively enrolled five patients with symptomatic cCMV infection, four with asymptomatic cCMV infection with isolated sensorineural hearing loss (SNHL), and five with asymptomatic cCMV infection. The plasma samples were collected during neonatal period. The peptides were analyzed using liquid chromatography-mass spectrometry. The concentrations of differentially expressed proteins were validated using an enzyme-linked immunosorbent assay. RESULTS: A total of 456 proteins were identified and quantified. The levels of 80 proteins were significantly different between patients with and without cCMV-related symptoms including isolated SNHL. The levels of 31 proteins were significantly different between patients with and without neuroimaging abnormalities. The plasma concentrations of Fms-related receptor tyrosine kinase 4 in patients with cCMV-related symptoms were significantly higher than those in patients with asymptomatic cCMV infection. Moreover, plasma peptidylprolyl isomerase A levels were significantly higher in patients with neuroimaging abnormalities than in those without. CONCLUSIONS: Proteomic analysis of patients with cCMV infection showed that Fms-related receptor tyrosine kinase 4 and peptidylprolyl isomerase A could be novel diagnostic biomarkers for neurological complications of cCMV infection.

Time course of skin rash, computed tomography findings, and viral load in a rheumatoid arthritis patient with severe varicella pneumonia.

Varicella-zoster virus (VZV) infection in adults or immunocompromised patients has a more severe presentation compared to the mild disease in children. To the best of our knowledge, no reports have described the clinical course of VZV pneumonia focusing on time course of skin rash, chest computed tomography (CT) findings, and viral load. Furthermore, no reports have described the reactivation of human herpes virus 6 (HHV-6) in VZV pneumonia. Here, we report a case of severe VZV pneumonia that resulted in reactivation of HHV-6 in a patient with rheumatoid arthritis (RA). A 66-year-old female treated for RA was admitted to our hospital with papules. Her chest CT showed granular infiltrates, micronodules, and ground-glass opacities. The day after admission, because the typical skin rashes and chest CT findings were observed, she was diagnosed with VZV pneumonia and treated with acyclovir. Her skin rash then crusted over five days and entered the healing process, whereas it took approximately two weeks for her respiratory condition and chest CT findings to improve. In addition, VZV deoxyribonucleic acid (DNA) gradually decreased with treatment. On the 34th day of admission, VZV DNA was not found in the serum sample but remained in the sputum sample. Furthermore, although reactivation of HHV-6 was observed, viremia resolved without treatment. Clinicians should be able to recognize the differences in the improvement of skin rashes, respiratory status, and chest CT findings. In addition, treatment for HHV-6 reactivation should be carefully determined for each case.

Next-generation sequencing-based detection of Ureaplasma in the gastric fluid of neonates with respiratory distress and chorioamnionitis.

BACKGROUND: Respiratory distress is common in neonates admitted to neonatal intensive care units. Additionally, infectious diseases such as intrauterine infections or vertical transmission are important underlying causes of respiratory failure. However, pathogens often cannot be identified in neonates, and there are many cases in which antibacterial drugs are empirically administered. Next-generation sequencing (NGS) is advantageous in that it can detect trace amounts of bacteria that cannot be detected by culturing or bacteria that are difficult to cultivate. However, there are few reports on the diagnosis of infectious diseases using NGS in the neonatal field, especially those targeting respiratory distress. OBJECTIVE: The purpose of our study was to investigate the microorganisms associated with neonatal respiratory distress and to determine whether less invasive collection specimens such as plasma and gastric fluid are useful. METHODS: Neonates were prospectively recruited between January and August 2020 from Nagoya University Hospital. The inclusion criteria were as follows: 1) admission to the neonatal intensive care unit; 2) respiratory distress presentation within 48 h of birth; and 3) suspected infection, collection of blood culture, and administration of antibiotics. Plasma samples and blood cultures were simultaneously collected. Gastric fluid samples were also collected if the patient was not started on enteral nutrition. Information on the patients and their mothers were collected from the medical records. DNA was extracted from 140 µL of plasma and gastric fluid samples. DNA sequencing libraries were prepared, and their quality was analyzed. DNA libraries were sequenced using high-throughput NGS. The NGS data of plasma and gastric fluid samples were analyzed using the metagenomic pipeline PATHDET, which calculated the number of reads assigned to microorganisms and their relative abundance. Putative pathogens were listed. RESULTS: Overall, 30 plasma samples and 25 gastric fluid samples from 30 neonates were analyzed. Microorganism-derived reads of gastric fluid samples were significantly higher than those of plasma samples. Transient tachypnea of the newborn was the most common cause of respiratory distress with 13 cases (43%), followed by respiratory distress syndrome with 7 cases (23%). There were 8 cases (29%) of chorioamnionitis and 7 cases (25%) of funisitis pathologically diagnosed. All blood cultures were negative, and only two gastric fluid cultures were positive for group B Streptococcus (Patient 15) and Candida albicans (Patient 24). Putative pathogens that met the positive criteria for PATHET were detected in four gastric fluid samples, one of which was group B Streptococcus from Patient 15. In the gastric fluid sample of Patient 24, Candida albicans were detected by NGS but did not meet the positive criteria for PATHDET. Cluster analysis of the plasma samples divided them into two study groups, and the indicator genera of each cluster (Phormidium or Toxoplasma) are shown in Figure 1. Clinical findings did not show any significant differences between the two groups. Cluster analysis of the gastric fluid samples divided them into three study groups, and the indicator genera of each cluster (Ureaplasma, Nostoc, and Streptococcus) are shown in Figure 2. The incidence rate of chorioamnionitis was significantly higher in Ureaplasma group than in the other two groups. CONCLUSION: Gastric fluid may be useful for assessing neonatal patients with respiratory distress. To the best of our knowledge, this was the first study to reveal that the presence of Ureaplasma in the gastric fluid of neonates with respiratory distress was associated with chorioamnionitis. The early diagnosis of intra-amniotic infections using gastric fluid and its treatment may change the treatment strategy for neonatal respiratory distress. Screening for Ureaplasma in neonates with respiratory distress may reduce the need for empirical antibiotic administration. Further research is required to confirm these findings.

Human leukocyte antigen 7/8-matched unrelated bone marrow transplantation using anti-thymocyte globulin in children.

Human leukocyte antigen (HLA) mismatched unrelated donor transplantation is associated with an increased risk of graft-versus-host disease, graft failure, and infection, which increases post-transplant morbidity and mortality. In this single-center retrospective study, outcomes were evaluated in 30 consecutive children who underwent bone marrow transplantation (BMT) from HLA 1 allele-mismatched (HLA 7/8-matched) unrelated donors with rabbit anti-thymocyte globulin (rATG) as graft-versus-host disease (GVHD) prophylaxis. The 3-year overall survival (OS), event-free survival (EFS), and GVHD-relapse-free survival rates were 91.7% (95% CI 70.5%-91.9%), 88.3% (95% CI 67.5%-96.1%), and 73.9% (95% CI 52.4%-86.8%), respectively. Grade II-IV and III-IV acute GVHD occurred in 10 (33%) and 2 (7.0%) patients, respectively. The 3-year cumulative incidence of chronic GVHD was 7.8%. No fatal viral infections occurred. The study results show the feasibility of HLA 7/8-matched unrelated BMT with ATG to achieve favorable outcomes and acceptable GVHD, especially for patients who lack a fully matched donor.

Droplet Digital PCR Development for Adenovirus Load Monitoring in Children after Hematopoietic Stem Cell Transplantation.

Human adenovirus (AdV) reactivation after hematopoietic stem cell transplantation (HSCT) is associated with life-threatening clinical manifestations. Although real-tme quantitative PCR (qPCR) has been widely used to measure AdV loads, it has not been standardized for AdV. Droplet digital PCR (ddPCR) is a novel pathogen detection technology that enables the absolute quantification of viral loads. ddPCR would enable a more accurate AdV DNA detection compared with qPCR. In this study, ddPCR was developed for AdV DNA and its performance characteristics compared with those of qPCR. AdV DNAemia incidence during the first 12 weeks after allogenic HSCT was then retrospectively examined by qPCR and ddPCR in 97 HSCT procedures using the preserved 545 DNA samples. ddPCR exhibited better reproducibility and sensitivity, as well as equivalent quantifiability, compared with qPCR. AdV DNA among HSCT patients was detected in 11 (2.0%) and 49 (9.0%) of 545 samples by qPCR and ddPCR, respectively. AdV DNA levels >1000 copies/mL were observed in five cases by qPCR and/or ddPCR. However, two patients developed fulminant hepatitis and died; other patients remained asymptomatic with subsequently undetectable AdV DNA. In conclusion, ddPCR was more sensitive and reproducible in detecting AdV DNA among pediatric HSCT recipients than qPCR. ddPCR offers the potential to provide a more accurate DNAemia detection, determine cutoff values for treatment initiation, and enable antiviral efficacy assessment.

Correlation of cytomegalovirus viral load between whole blood and plasma of congenital cytomegalovirus infection under valganciclovir treatment.

BACKGROUND: Congenital cytomegalovirus (CMV) infection (cCMV) can cause sensorineural hearing loss and neurodevelopmental disabilities in children. Oral valganciclovir (VGCV) therapy has been reported to improve long-term audiological and neurodevelopmental outcomes in patients with cCMV. The levels of CMV DNA in whole blood have been monitored in previous studies. However, quantitative methods using whole blood have not been standardized. Recently, the plasma viral load has been standardized and widely used in CMV-associated diseases. METHODS: CMV viral loads in whole blood and plasma were serially measured in 24 patients with a confirmatory diagnosis of cCMV during oral VGCV therapy using an in-house real-time PCR assay. Plasma samples were assayed using the Cobas 6800 system (Roche Diagnostics) in addition to an in-house assay. RESULTS: Plasma CMV viral loads were remarkably decreased at the end of therapy compared to before therapy. A significant correlation of CMV levels between whole blood and plasma was observed (Spearman's ρ = 0.566). The levels of CMV DNA before therapy were significantly correlated with the period of decreasing the viral loads to below the detection limit, not only in whole blood (Spearman's ρ = 0.901) but also in plasma (Spearman, ρ = 0.804). Finally, CMV viral loads between the in-house assay and commercially available standardized assay in 75 plasma samples with positive PCR results for CMV were compared; a significant correlation was observed between the results of both assays. CONCLUSIONS: There was a significant correlation between the two assays (Spearman, ρ = 0.882), suggesting that CMV plasma viral loads measured by the standardized assay are widely used to monitor the levels of CMV DNA in patients with cCMV during oral VGCV therapy.

Performance of Nanopore and Illumina Metagenomic Sequencing for Pathogen Detection and Transcriptome Analysis in Infantile Central Nervous System Infections.

Background: Infantile central nervous system infections (CNSIs) can be life-threatening and cause severe sequelae. However, the causative microorganism remains unknown in >40% of patients with aseptic infections. This study aimed to analyze the metagenome for detection of pathogens and the transcriptome for host immune responses during infection in a single cerebrospinal fluid (CSF) sample using 2 different next-generation sequencing (NGS) platforms, Nanopore and Illumina. Methods: Twenty-eight CNSIs patients (<12 months) were enrolled, and 49 clinical samples (28 CSF and 21 blood) were collected. The DNA extracted from all 49 samples was sequenced using the Illumina sequencer for the detection of pathogens. Extracted RNA was obtained in sufficient quantities from 23 CSF samples and subjected to sequencing on both Nanopore and Illumina platforms. Human-derived reads subtracted during pathogen detection were used for host transcriptomic analysis from both Nanopore and Illumina sequencing. Results: RNA metagenomic sequencing using both sequencing platforms revealed putative viral pathogens in 10 cases. DNA sequencing using the Illumina sequencer detected 2 pathogens. The results of Nanopore and Illumina RNA sequencing were consistent; however, the mapping coverage and depth to the detected pathogen genome of Nanopore RNA sequencing were greater than those of Illumina. Host transcriptomic analysis of Nanopore sequencing revealed highly expressed genes related to the antiviral roles of innate immunity from pathogen-identified cases. Conclusions: The use of Nanopore RNA sequencing for metagenomic diagnostics of CSF samples should help to elucidate both pathogens and host immune responses of CNSI and could shed light on the pathogenesis of these infections.

Post-exposure prophylaxis to prevent varicella in immunocompromised children.

Background: Varicella-zoster virus (VZV) infection can cause life-threatening events in immunocompromised patients. Post-exposure prophylaxis (PEP) is required to prevent secondary VZV infection. Limited evidence is available for the use of acyclovir (ACV)/valacyclovir (VCV) as PEP. Methods: Herein, we retrospectively analyzed immunocompromised paediatric patients with significant exposure to VZV. Patients administered PEP were categorized into four groups: 1) ACV/VCV group; 2) intravenous immunoglobulin (IVIG) group; 3) ACV/VCV/IVIG group; 4) vaccine group. Results: Among 69 exposure events, 107 patients were administered PEP (91, ACV/VCV; 16, ACV/VCV/IVIG) and 10 patients did not receive PEP (non-PEP group). The index case was diagnosed based on clinical symptoms in 55 cases (79.7%). Fourteen cases (20.3%) were confirmed using direct virological diagnostic procedures. In the PEP group, only 2 patients (2.2%) developed secondary VZV infections. Additionally, 2 patients in the non-PEP group (20.0%) developed secondary VZV infection. The incidence of secondary VZV infection was significantly lower in the PEP group than in the non-PEP group (P=0.036). Among patients administered PEP, no antiviral drug-induced side effects were detected. Conclusions: Antiviral agents administered as PEP are effective and safe for preventing VZV infections in immunocompromised patients. Rapid virological diagnosis of index cases might allow efficient administration of PEP after significant exposure to VZV infection.

Detection of antiviral drug resistance in patients with congenital cytomegalovirus infection using long-read sequencing: a retrospective observational study.

BACKGROUND: Congenital human cytomegalovirus (cCMV) infection can cause sensorineural hearing loss and neurodevelopmental disabilities in children. Ganciclovir and valganciclovir (GCV/VGCV) improve long-term audiologic and neurodevelopmental outcomes for patients with cCMV infection; however, antiviral drug resistance has been documented in some cases. Long-read sequencing can be used for the detection of drug resistance mutations. The objective of this study was to develop full-length analysis of UL97 and UL54, target genes with mutations that confer GCV/VGCV resistance using long-read sequencing, and investigate drug resistance mutation in patients with cCMV infection. METHODS: Drug resistance mutation analysis was retrospectively performed in 11 patients with cCMV infection treated with GCV/VGCV. UL97 and UL54 genes were amplified using blood DNA. The amplicons were sequenced using a long-read sequencer and aligned with the reference gene. Single nucleotide variants were detected and replaced with the reference sequence. The replaced sequence was submitted to a mutation resistance analyzer, which is an open platform for drug resistance mutations. RESULTS: Two drug resistance mutations (UL54 V823A and UL97 A594V) were found in one patient. Both mutations emerged after 6 months of therapy, where viral load increased. Mutation rates subsided after cessation of GCV/VGCV treatment. CONCLUSIONS: Antiviral drug resistance can emerge in patients with cCMV receiving long-term therapy. Full-length analysis of UL97 and UL54 via long-read sequencing enabled the rapid and comprehensive detection of drug resistance mutations.

Quantitative assessment of viral load in the blood and urine of patients with congenital cytomegalovirus infection using droplet digital PCR.

Congenital cytomegalovirus infection (cCMV) is a common cause of congenital infections, leading to neurodevelopmental sequelae. Real-time quantitative polymerase chain reaction (qPCR) has been widely used for the diagnosis and assessment of cCMV; however, the correlation between CMV DNA load and the severity of cCMV symptoms has been inconclusive. Droplet digital PCR (ddPCR) offers an improvement over the current qPCR methods through the absolute quantification of viral loads. We compared ddPCR and qPCR results for the quantification of CMV DNA in blood and urine specimens from 39 neonates with cCMV (21 symptomatic and 18 asymptomatic). There was no significant difference in blood CMV DNA loads measured by ddPCR and qPCR, with or without any clinical findings. However, developmental delays at 36 months were significantly more frequently observed in patients with high CMV DNA loads (≥2950 copies/ml), as measured by ddPCR at diagnosis, than in those with lower CMV DNA loads. The association of urine CMV DNA load with symptoms and developmental delay was not observed. CMV DNA loads in the blood might be used as a predictor of developmental outcomes in cCMV patients, and absolute quantitation of viral loads by ddPCR assay could contribute to the standardization of CMV load measurement.

MicroRNA expression profiling of cerebrospinal fluid/serum exosomes in children with human herpesvirus 6-associated encephalitis/encephalopathy by high-throughput sequencing.

Primary human herpesvirus 6 (HHV-6) infection is sometimes accompanied by acute encephalopathy with reduced subcortical diffusion (AED) in immunocompetent children. We investigated exosomal microRNA (miRNA) expression profiles in cerebrospinal fluid (CSF) and sera of patients with HHV-6-associated AED (n = 5) and febrile seizure (FS) (n = 5) using high-throughput sequencing. A total of 176 and 663 miRNAs were identified in CSF and serum exosomes, respectively. Comparative analysis determined that some miRNAs (miR-381-3p, miR-155) were exclusively expressed in the CSF exosomes of AED but not of FS patients, suggesting their potential application as novel diagnostic biomarkers for AED.

Next-Generation Sequencing to Detect Pathogens in Pediatric Febrile Neutropenia: A Single-Center Retrospective Study of 112 Cases.

BACKGROUND: Febrile neutropenia (FN) is a frequent complication in immunocompromised patients. However, causative microorganisms are detected in only 10% of patients. This study aimed to detect the microorganisms that cause FN using next-generation sequencing (NGS) to identify the genome derived from pathogenic microorganisms in the bloodstream. Here, we implemented a metagenomic approach to comprehensively analyze microorganisms present in clinical samples from patients with FN. METHODS: FN is defined as a neutrophil count <500 cells/µL and fever ≥37.5°C. Plasma/serum samples of 112 pediatric patients with FN and 10 patients with neutropenia without fever (NE) were sequenced by NGS and analyzed by a metagenomic pipeline, PATHDET. RESULTS: The putative pathogens were detected by NGS in 5 of 10 FN patients with positive blood culture results, 15 of 87 FN patients (17%) with negative blood culture results, and 3 of 8 NE patients. Several bacteria that were common in the oral, skin, and gut flora were commonly detected in blood samples, suggesting translocation of the human microbiota to the bloodstream in the setting of neutropenia. The cluster analysis of the microbiota in blood samples using NGS demonstrated that the representative bacteria of each cluster were mostly consistent with the pathogens in each patient. CONCLUSIONS: NGS technique has great potential for detecting causative pathogens in patients with FN. Cluster analysis, which extracts characteristic microorganisms from a complex microbial population, may be effective to detect pathogens in minute quantities of microbiota, such as those from the bloodstream.

[Recent advances in pathophysiology, diagnosis and treatment of steroid-refractory graft-versus-host disease].

Acute graft-versus-host disease (GVHD) is a major life-threating complication that occurs after allogeneic cell transplantation. Although steroids remain the first-line treatment, approximately one-third of patients will eventually develop steroid-resistant or steroid-refractory GVHD (SR-GVHD), which has an extremely poor prognosis. Many novel strategies that showed promising response rates in early phase I/II trials for the prevention and treatment of acute GVHD exhibited disappointing effects on patient survival in the SR-GVHD setting. The discovery of novel treatments has been further complicated by the absence of a clinically-relevant animal model. Nevertheless, the combined knowledge from translational studies using bone marrow transplantation models and clinical trials including SR-GVHD patients has begun to reveal novel mechanisms for inhibiting T cell signaling and promoting tissue regeneration, which has contributed to a better understanding of the SR-GVHD pathophysiology. Herein, we discuss recently elucidated cellular and molecular mechanisms that may provide the rational for novel biologically-driven treatments for SR-GVHD.

A Case of Descending Necrotizing Mediastinitis in a Previously Healthy Child.

Descending necrotizing mediastinitis (DNM) is a rare complication of oropharyngeal and cervical infection, especially in children. We report a case of DNM secondary to a cervical abscess in a previously healthy 1-year-old boy. The patient presented with redness and swelling of the neck and fever. He was treated with an antimicrobial agent for the diagnosis of cervical lymphadenitis. On the sixth day, a huge mediastinal abscess was found, and he was admitted to the intensive care unit. He was successfully treated with surgical drainage and appropriate antimicrobial therapy. The pus culture isolated multiple bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Although we did not use an antimicrobial agent covering MRSA, the symptoms and test results improved. Washing with drainage was effective. The patient required multidisciplinary treatment, and we collaborated with specialists in other departments. DNM is a severe disease in which team medical care is needed to provide appropriate treatment.

Pediatric sepsis cases diagnosed with group B streptococcal meningitis using next-generation sequencing: a report of two cases.

BACKGROUND: Group B Streptococcus (GBS) is an important cause of invasive infection in neonates and infants. Cerebrospinal fluid (CSF) findings and culture may not show evidence of infection early in GBS meningitis. Next-generation sequencing (NGS) has the potential to detect microbial genetic material in patients with infectious diseases. We report two cases of infantile sepsis of GBS meningitis with negative results for CSF culture tests, but positive results for NGS analysis. CASE PRESENTATION: Patient 1 was a 22-day-old male infant diagnosed with sepsis and meningitis. His CSF findings showed pleocytosis, decreased glucose, and increased protein levels. However, CSF and blood culture results at admission were negative. He received a total of 3 weeks of treatment with ampicillin and cefotaxime, and showed clinical improvement. GBS was detected through NGS analysis of CSF collected at admission. Patient 2 was a 51-day-old male infant with sepsis. CSF findings on admission were normal, and blood and CSF cultures were also negative. Intravenous ampicillin and cefotaxime treatment were initiated. Treatment was de-escalated to ampicillin alone because Enterococcus faecalis was cultured from urine. He was discharged after a total of 1 week of antibiotic treatment. Six days after discharge, he was re-hospitalized for sepsis. Blood and CSF cultures were negative, and E. faecalis was again cultured from urine. He received a total of 3 weeks of ampicillin treatment for enterococcal-induced nephritis and did not relapse thereafter. NGS pathogen searches were retrospectively performed on both blood and CSF collected at the first and second admission. GBS was detected in the CSF collected at the first admission, but no significant pathogen was detected in the other samples. Inadequate treatment for GBS meningitis at the first admission may have caused the recurrence of the disease. CONCLUSION: Infantile sepsis may present bacterial meningitis that is not diagnosed by either culture testing or CSF findings. NGS analysis for CSF may be useful for confirming the diagnosis of bacterial meningitis.