Seroprevalence of severe acute respiratory syndrome coronavirus 2 N antibodies between December 2021 and march 2023 in Japan.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in 2019 in China and rapidly spread worldwide, leading to a pandemic. The threat of SARS-CoV-2 is subsiding as most people have acquired sufficient antibodies through vaccination and/or infection to prevent severe COVID-19. After the emergence of the omicron variants, the seroprevalence of antibodies against the N protein elicited by SARS-CoV-2 infection ranged from 44.4% to 80.2% in countries other than Japan. Here, we assessed the seroprevalence in Japan before and after the appearance of omicron variants. Serosurveillance of antibodies against N was conducted between December 2021 and March 2023 in Japan. In total, 7604 and 3354 residual serum or plasma samples were collected in the Tokyo metropolitan area and Sapporo, respectively. We found that the seroprevalence in representative regions of Japan increased approximately 3% to 23% after the emergence of the omicron variants. We also found higher seroprevalence among the young compared with the elderly. Our findings indicate that unlike other countries, most of the Japanese population has not been infected, raising the possibility of future SARS-CoV-2 epidemics in Japan.

Nail-patella syndrome with nephropathy in a de novo LMX1B mutation: triangular lunula of the thumb and lack of finger creases as clues.

Nail-patella syndrome (NPS) is an autosomal dominant disease caused mostly by mutations in the LMX1B gene and is characterized by hypoplastic nails, hypoplastic patella, elbow deformities, glaucoma, and nephropathy, sometimes leading to kidney failure. The combination and the severity of symptoms vary greatly from patient to patient. Because a kidney biopsy may show nonspecific findings, patients with nephropathy alone may not be diagnosed without undergoing genetic testing. We examined the case of a 6-year-old girl with persistent high proteinuria who was not diagnosed by kidney biopsy but had a diagnosis of a de novo mutation in the LMX1B gene following genetic testing. Retrospectively, only the thumbs showed triangular lunulae, while the third and fourth fingers lacked skin creases over the distal interphalangeal joints, which is subtle but characteristic of NPS. Notifying pediatric nephrologists of these findings can help avoid unnecessary kidney biopsies and lead to early detection of the disease.

Age-Stratified Seroprevalence of SARS-CoV-2 Antibodies before and during the Vaccination Era, Japan, February 2020-March 2022.

Japan has reported a relatively small number of COVID-19 cases. Because not all infected persons receive diagnostic tests for COVID-19, the reported number must be lower than the actual number of infections. We assessed SARS-CoV-2 seroprevalence by analyzing >60,000 samples collected in Japan (Tokyo Metropolitan Area and Hokkaido Prefecture) during February 2020-March 2022. The results showed that ≈3.8% of the population had become seropositive by January 2021. The seroprevalence increased with the administration of vaccinations; however, among the elderly, seroprevalence was not as high as the vaccination rate. Among children, who were not eligible for vaccination, infection was spread during the epidemic waves caused by the SARS-CoV-2 Delta and Omicron variants. Nevertheless, seroprevalence for unvaccinated children <5 years of age was as low as 10% as of March 2022. Our study underscores the low incidence of SARS-CoV-2 infection in Japan and the effects of vaccination on immunity at the population level.

The first case report of pediatric acute appendicitis caused by "Candidatus Actinobaculum timonae".

A 14-year-old boy presented to the hospital with pain in the right lower abdomen. His condition was diagnosed as acute appendicitis. An emergency operation was performed, and histopathological examination revealed an actinomycete-related organism in the excised appendicitis specimen. On 16S rRNA gene sequence analysis, "Candidatus Actinobaculum timonae" was identified, which is the first known case in a pediatric patient.

Shortfall of exome analysis for diagnosis of Shwachman-Diamond syndrome: Mismapping due to the pseudogene SBDSP1.

Shwachman-Diamond syndrome characterized by metaphyseal dysplasia, pancreatic insufficiency, and pancytopenia is caused by biallelic mutations in SBDS. Gene conversion between SBDS and its pseudogene SBDSP1 is the major cause. Here, we report two unrelated patients with Shwachman-Diamond syndrome who were shown to be compound heterozygotes for relatively frequent pathogenic alleles (the 258+2T>C allele and another allele composed of 183-184TA>CT and 201A>G) using an established polymerase chain reaction sequencing assay with SBDS-specific primers. Exome analysis of the patients showed discrepant results: 258+2T>C with variant allele frequency around 0.85, and no variants detected for the 183-184TA>CT allele. Parental exome analysis of the two families further supported this notion. Confronted with two patients with an unexpected segregation pattern, we performed a transcriptome analysis of peripheral blood-derived mRNA to demonstrate that the results were compatible with those obtained using SBDS-specific PCR primers. Both alleles could be accounted for by gene conversion events. The diagnostic discrepancy can be accounted for by a decreased efficiency in the computational mapping of the reads with 183-184TA>CT and 201A>G to the reference sequence of the SBDS locus during exome analysis. This report highlights the pitfall of exome analysis for genes with pseudogenes, such as SBDS and the alternative use of RNA-seq is recommended to circumvent this problem.

Verification of blood volume for blood culture and detection rate in pediatrics.

PURPOSE: This study was conducted to estimate the blood culture volume that should be collected from pediatric patients to improve diagnostic abilities. METHODS: Blood cultures from neonates and children aged up to 18 years were collected and the volume was measured for over a 1-year period. During the intervention period, examiners were instructed to draw 3 mL of blood for culture, if possible. The pre-intervention period was from June 1 to August 31, 2016. The post-intervention period was from September 1, 2016, to May 30, 2017. The rate of positive detections was calculated and compared between pre and post-intervention periods. RESULTS: We collected 1352 samples and measured 1327 bottles. During the pre-intervention period, 340 cases were collected with a median blood volume of 1.64 mL; 9 cases (2.7%) were true-positive. During the intervention period, 1012 cases were ordered with a median blood volume of 2.41 mL; 19 cases (1.9%) were true-positive. After intervention, blood volume was increased significantly (p < 0.01). However, there was no significant difference in the rate of positive detections during the study periods (p = 0.254). CONCLUSIONS: In the pediatric clinical setting in a Japanese municipal hospital, the positive detection rate did not improve even when the collected blood volume was increased. One milliliter of blood volume may be adequate for the pediatric bottle in children.

One-month-old boy with group B streptococcal meningitis, subdural effusion, and high levels of interleukin-6.

Meningitis is associated with elevated levels of inflammatory cytokines in the blood, cerebrospinal fluid (CSF), and subdural fluid. Subdural effusion prolongs fever in patients with meningitis. However, the reason for this remains unclear. A healthy one-month-old boy was admitted after presenting with bacterial meningitis. He was administered meropenem, cefotaxime, and dexamethasone intravenously. On the 3rd day, blood and CSF cultures revealed the presence of Group B Streptococcus from samples collected on day 1. Subsequently, ampicillin and gentamicin replaced the previous combination of antimicrobials used. On the 4th day, brain magnetic resonance imaging with contrast showed bilateral cerebral ventriculitis and left subdural effusion. On the 11th day, since the subdural effusion had worsened, we performed a subdural puncture from the anterior fontanelle. Owing to the prolonged fever, he was intravenously injected immunoglobulin on day 13. He was afebrile on day 23. Antimicrobials were administered for 28 days. Levels of interleukin-6 (IL-6) in the serum and CSF were the highest on the 1st day at 20,600 pg/mL and 170,000 pg/mL, respectively, and decreased upon treatment. IL-6 concentration in the subdural fluid (30,000 pg/mL) was much higher than that in the serum (9 pg/mL) and CSF (2600 pg/mL). To the best of our knowledge, this is the first report on the cytokines in subdural fluid in patients with group B Streptococcal meningitis. Subdural effusion maintained high levels of IL-6 even after the levels in the blood and CSF decreased dramatically. This could explain why subdural effusion prolongs fever in patients with meningitis.

Purulent lymphadenitis caused by Staphylococcus argenteus, representing the first Japanese case of Staphylococcus argenteus (multilocus sequence type 2250) infection in a 12-year-old boy.

Staphylococcus argenteus is a novel species separated from a strain of coagulase-positive, non-pigmented S. aureus. Although S. argenteus has been reported to occur globally, multilocus sequence type (ST) 2250 is mainly found in Northeastern Thailand. Because conventional biochemical testing misidentifies this pathogen as S. aureus, multilocus sequence typing (MLST) or nucA sequencing is recommended to distinguish between S. argenteus and S. auereus. The patient was a previously healthy 12-year-old boy who was admitted because of right inguinal lymphadenitis and cellulitis. Although intravenous cefazolin was administered, his lymphadenitis worsened and formed an abscess on day 6 of hospitalization. Incision and drainage were performed on day 7 of hospitalization. Cefazolin was changed to oral cefaclor, and the patient was successfully treated over a period of 5 weeks. No recurrence was observed throughout 12-months of follow-up. He had a history of right axillary lymph node abscess 2 months before this admission, which was successfully treated with incision, drainage, and antibiotic therapy. He has lived in Japan since birth and never traveled abroad. He had no opportunity to interact with foreigners. His immune function, especially neutrophil function, was tested and we did not find any dysfunction. First, methicillin-sensitive S. aureus was misidentified from the abscess culture. Subsequently, the causative agent was re-identified as S. argenteus ST2250 based on MLST. To our knowledge, this is the first case of S. argenteus ST2250 infection in Japan. This pathogen should be taken into consideration in the diagnosis if the patient has atypical non-pigmented S. aureus.

Loss of function mutations in RPL27 and RPS27 identified by whole-exome sequencing in Diamond-Blackfan anaemia.

Diamond-Blackfan anaemia is a congenital bone marrow failure syndrome that is characterized by red blood cell aplasia. The disease has been associated with mutations or large deletions in 11 ribosomal protein genes including RPS7, RPS10, RPS17, RPS19, RPS24, RPS26, RPS29, RPL5, RPL11, RPL26 and RPL35A as well as GATA1 in more than 50% of patients. However, the molecular aetiology of many Diamond-Blackfan anaemia cases remains to be uncovered. To identify new mutations responsible for Diamond-Blackfan anaemia, we performed whole-exome sequencing analysis of 48 patients with no documented mutations/deletions involving known Diamond-Blackfan anaemia genes except for RPS7, RPL26, RPS29 and GATA1. Here, we identified a de novo splicing error mutation in RPL27 and frameshift deletion in RPS27 in sporadic patients with Diamond-Blackfan anaemia. In vitro knockdown of gene expression disturbed pre-ribosomal RNA processing. Zebrafish models of rpl27 and rps27 mutations showed impairments of erythrocyte production and tail and/or brain development. Additional novel mutations were found in eight patients, including RPL3L, RPL6, RPL7L1T, RPL8, RPL13, RPL14, RPL18A and RPL31. In conclusion, we identified novel germline mutations of two ribosomal protein genes responsible for Diamond-Blackfan anaemia, further confirming the concept that mutations in ribosomal protein genes lead to Diamond-Blackfan anaemia.

Severe immune thrombocytopenia that developed immediately after COVID-19 in a school-aged patient: A case report.

Immune thrombocytopenia (ITP) is an autoimmune disorder that is sometimes triggered by a preceding viral infection and is characterized by a transient or persistent decrease in the platelet (Plt) count. Herein, we report the first pediatric case of severe ITP that developed immediately after the diagnosis of coronavirus disease 2019 (COVID-19) in a school-aged girl. A previously healthy six-year-old girl was diagnosed with COVID-19 a day before experiencing a high fever, sore throat, and headache. She also presented with gingival hemorrhage, petechiae around both eyes and on the chest, and ecchymosis on her right leg. Based on the mucosal hemorrhage and a very low Plt count of 3 × 103/µl, we diagnosed her with severe ITP and urgently treated her with intravenous immunoglobulin (IVIG) to prevent life-threatening hemorrhage. The Plt count increased to 266 × 103/µl one week after treatment with IVIG. Given the possibility of severe ITP secondary to COVID-19, patients with COVID-19 should be carefully examined for the signs of ITP, such as mucosal hemorrhage. Their Plt counts should also be monitored.

Yersinia pseudotuberculosis Infection Accompanied by Intussusception and Incomplete Kawasaki Disease in a 7-year-old Girl.

Infection with Yersinia pseudotuberculosis, a known causal pathogen of human bacterial gastroenteritis, causes various symptoms and complications. A previously healthy 7-year-old girl was admitted because of fever and gastrointestinal symptoms. She was initially diagnosed with intussusception by abdominal ultrasonography. Although the patient was successfully treated by air enema, the fever persisted. The patient was then diagnosed with incomplete Kawasaki disease based on the presence of four principal clinical features. Intravenous immunoglobulin and oral aspirin were initiated. The patient defervesced and the other symptoms subsided after the treatment. Cardiac ultrasound results showed normal coronary arteries. Because of the gastrointestinal symptoms, stool samples were cultured repeatedly, only to yield normal flora. However, serum levels of anti-Y. pseudotuberculosis-derived mitogen antibody were elevated between the 7th and 18th days of the disease, thereby confirming Y. pseudotuberculosis infection. Because Y. pseudotuberculosis infection results in various clinical manifestations, we must be aware of each symptom and address them systematically.

Clinical features and treatment strategies of febrile urinary tract infection caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae in children: a multicenter retrospective observational study in Japan.

OBJECTIVES: The incidence of infections caused by extended-spectrum beta-lactamase (ESBL)-producing bacteria has increased. This study aimed to clarify the risk factors and treatment strategies for febrile urinary tract infection (fUTI) caused by ESBL-producing bacteria in Japanese children. METHODS: A retrospective observational study was conducted in 21 hospitals among children aged <16 years diagnosed with an fUTI between 2008 and 2017. Clinical data of children with fUTI caused by ESBL-producing and non-ESBL-producing bacteria were compared. RESULTS: Of the 2049 cases of fUTI, 147 (7.2%) were caused by ESBL-producing bacteria. Children in the ESBL group were more likely to have a history of recent antibiotic use or prophylactic antibiotic use, and experience recurrent UTIs (P <0.001) compared with those in the non-ESBL group. Of the 124 cases of fUTI due to ESBL-producing bacteria that were reviewed, 20 and 100 had concordant and discordant antibiotic use, respectively, and four had unknown antibiotic susceptibility. The median time from the start of treatment to fever resolution was 24 hours and did not differ significantly by therapy group (P = 0.39). CONCLUSION: ESBL-producing bacteria should be considered in children with recurrent UTIs and recent antibiotic use. Most children with fUTI experience clinical improvement regardless of the choice of antibiotic.

Trends in effectiveness of inactivated influenza vaccine in children by age groups in seven seasons immediately before the COVID-19 era.

BACKGROUND: We have reported the vaccine effectiveness of inactivated influenza vaccine in children aged 6 months to 15 years between the 2013/14 and 2018/19 seasons. Younger (6-11 months) and older (6-15 years old) children tended to have lower vaccine effectiveness. The purpose of this study is to investigate whether the recent vaccine can be recommended to all age groups. METHODS: The overall adjusted vaccine effectiveness was assessed from the 2013/14 until the 2020/21 season using a test-negative case-control design based on rapid influenza diagnostic test results. Vaccine effectiveness was calculated by influenza type and by age group (6-11 months, 1-2, 3-5, 6-12, and 13-15 years old) with adjustments including influenza seasons. RESULTS: A total of 29,400 children (9347, 4435, and 15,618 for influenza A and B, and test-negatives, respectively) were enrolled. The overall vaccine effectiveness against influenza A, A(H1N1)pdm09, and B was significant (44% [95% confidence interval (CI), 41-47], 63% [95 %CI, 51-72], and 37% [95 %CI, 32-42], respectively). The vaccine was significantly effective against influenza A and B, except among children 6 to 11 months against influenza B. The age group with the highest vaccine effectiveness was 1 to 2 years old with both influenza A and B (60% [95 %CI, 55-65] and 52% [95 %CI, 41-61], respectively). Analysis for the 2020/21 season was not performed because no cases were reported. CONCLUSIONS: This is the first report showing influenza vaccine effectiveness by age group in children for several seasons, including immediately before the coronavirus disease (COVID-19) era. The fact that significant vaccine effectiveness was observed in nearly every age group and every season shows that the recent vaccine can still be recommended to children for the upcoming influenza seasons, during and after the COVID-19 era.

Clinical characteristics of pediatric febrile urinary tract infection in Japan.

BACKGROUND: Febrile urinary tract infection (fUTI) is the most common serious bacterial infection in children. Despite this, there have been no studies examining the clinical features of pediatric fUTI in Japan. The purpose of this study was to describe the clinical characteristics of fUTI in Japanese children. METHODS: A multicenter, retrospective, observational study was conducted at 21 hospitals in Japan. Children under the age of 15 years who were diagnosed with fUTI between 2008 and 2017 were included. The diagnostic criteria were a temperature over 38 °C and the presence of a single bacterial pathogen in urine culture. Patient characteristics were obtained from medical records. RESULTS: In total, 2,049 children were included in the study. The median age was 5 months, and 59.3% were male. It was found that 87.0% of the males and 53.2% of the females were under 1 year of age. The main causative pathogens identified were Escherichia coli and Enterococcus spp., accounting for 76.6% and 9.8% of infections, respectively. CONCLUSIONS: There was a male predominance of fUTI in Japanese children, particularly in infants. Enterococcus spp. were the second most frequent causative pathogen; therefore, Gram staining of urine samples is strongly recommended before initiating antibiotic therapy.

A novel screening method for pediatric urinary tract infection using ordinary diapers.

Urinary tract infection (UTI) is one of the most common bacterial infections in children. The symptoms of UTI in young children are nonspecific, therefore urine should be examined whenever UTI cannot be ruled out. In clinical settings, however, collecting urine from children who are not toilet trained is sometimes difficult, presenting a challenge in UTI management. Here, we developed a "diaper UTI test", which enables the quick detection of pyuria in ordinary diapers, and investigated its sensitivity and specificity in a clinical study. The diaper UTI test is based on a leukocyte esterase reaction. Reagent was prepared in liquid form so that it can be absorbed by disposable diapers, where it will produce a violet color in the presence of pyuria. For the clinical study, we enrolled children younger than 3 years with potential UTI who underwent bladder catheterization for urine culture and urinalysis. Of the 65 children included, 21 were diagnosed with UTI. The sensitivity and specificity of the diaper UTI test were 90.5% (95% CI 69.6-98.8) and 93.2% (95% CI 81.3-98.6), respectively. Because of its convenience and good sensitivity, the diaper UTI test may be useful in the screening of pediatric UTI.

Clinical Features of Febrile Urinary Tract Infection Caused by Extended-spectrum Beta-lactamase-producing Escherichia Coli in Children.

The global prevalence of infections caused by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli has been increasing. In children, ESBL-producing E. coli manifest mostly as febrile urinary tract infections (fUTIs). This study aimed to elucidate the clinical features of fUTI resulting from ESBL-producing E. coli in Japanese patients. The clinical features of children with E. coli-related fUTI were retrospectively examined. These children underwent treatment at the National Hospital Organization Saitama Hospital, Japan, between May 2010 and April 2018. Urine specimens were obtained by either bladder catheterization or the clean-catch method. All children having positive urine cultures (≥104 colony-forming unit/mL for catheter specimens and ≥105 colony forming unit/mL for clean-catch specimens) and a fever of ≥38°C were considered to have fUTI. During the study period, 171 patients were diagnosed with E. coli-related fUTI. Among these, 17 (9.9%) fUTI cases were caused by ESBL-producing E. coli. A significant difference was noted in the median age of the populations having ESBL-producing E. coli and non-ESBL-producing E. coli infections (2 and 5 months, respectively); other characteristics were not significantly different between the two patient groups. ESBL-producing E. coli infections markedly increased in our hospital between 2013 and 2018. In the present study, young age was the only risk factor for fUTI caused by ESBL-producing E. coli identified in Japanese children.

Round pneumonia due to Chlamydia pneumoniae in a child.

Round pneumonia is a disease commonly recognized in the pediatric age group, especially under the age of 8 years. Streptococcus pneumoniae is the most common agent causing this characteristic type of pneumonia. We herein report a case of a 6-year-old boy with only mild cough and low-grade fever who was then diagnosed with round pneumonia due to Chlamydia pneumoniae. He had multiple round opacities in the right lower lung field, and the symptoms subsided soon after oral administration of antibiotics.