Acute and Postacute Clinical Characteristics of Coronavirus Disease 2019 in Children in Japan

BACKGROUND

The clinical features of coronavirus disease 2019 (COVID-19) in children have been changing because of the emergence and rapid spread of variants of concern (VOC). The increase in cases infected with VOC has brought concern with persistent symptoms after COVID-19 in children. This survey aimed to analyze the clinical manifestations and persistent symptoms of pediatric COVID-19 cases in Japan.

METHODS

We analyzed the clinical manifestations of pediatric COVID-19 cases reported between February 2020 and April 2022 in Japan, using a dedicated database updated voluntarily by the members of the Japan Pediatric Society. Using the same database, we also analyzed persistent symptoms after COVID-19 in children who were diagnosed between February 2020 and November 2021.

RESULTS

A total of 5411 and 1697 pediatric COVID-19 cases were included for analyzing clinical manifestations and persistent symptoms, respectively. During the Omicron variant predominant period, the percentage of patients with seizures increased to 13.4% and 7.4% in patient groups 1-4 and 5-11 years of age, respectively, compared with the pre-Delta (1.3%, 0.4%) or Delta period (3.1%, 0.0%). Persistent and present symptoms after 28 days of COVID-19 onset were reported in 55 (3.2%).

CONCLUSIONS

Our survey showed that the rate of symptomatic pediatric COVID-19 cases increased gradually, especially during the Omicron variant predominant period, and a certain percentage of pediatric cases had persistent symptoms. Certain percentages of pediatric COVID-19 patients had severe complications or prolonged symptoms. Further studies are needed to follow such patients.

The clinical characteristics of pediatric coronavirus disease 2019 in 2020 in Japan

BACKGROUND

The COVID-19 pandemic has affected the lives of people of all ages. Most reports on pediatric cases suggest that children experience fewer and milder symptoms than do adults. This is the first nationwide study in Japan focusing on pediatric cases reported by pediatricians, including cases with no or mild symptoms.

METHODS

We analyzed the epidemiological and clinical characteristics and transmission patterns of 840 pediatric (<16 years old) COVID-19 cases reported between February and December 2020 in Japan, using a dedicated database which was maintained voluntarily by members of the Japan Pediatric Society.

RESULTS

Almost half of the patients (47.7%) were asymptomatic, while most of the others presented mild symptoms. At the time of admission or first outpatient clinic visit, 84.0% of the cases were afebrile (<37.5°C). In total, 609 cases (72.5%) were exposed to COVID-19-positive household members. We analyzed the influence of nationwide school closures that were introduced in March 2020 on COVID-19 transmission routes among children in Japan. Transmission within households occurred most frequently, with no significant difference between the periods before and after declaring nationwide school closures (70.9% and 74.5%, respectively).

CONCLUSIONS

COVID-19 symptoms in children are less severe than those in adults. School closure appeared to have a limited effect on transmission. Controlling household transmission from adult family members is the most important measure for prevention of COVID-19 among children.

Recombinant thrombomodulin attenuates hyper-inflammation and glycocalyx damage in a murine model of Streptococcus pneumoniae-induced sepsis

PURPOSE

The anticoagulant agent recombinant thrombomodulin (rTM) activates protein C to prevent excessive coagulation and also possibly regulates hyper-inflammation via neutralization of high-mobility-group B1 (HMG-B1). The glycocalyx layer in endothelial cells also plays a pivotal role in preventing septic shock-associated hyperpermeability. The present study examined the effect of rTM in a murine model of Streptococcus pneumoniae-induced sepsis.

METHODS

Male C57BL/6N mice were injected intratracheally via midline cervical incision with 2 × 10⁷ CFU of S. pneumoniae (capsular subtype 19A). Control mice were sham-treated identically but injected with saline. rTM (10 mg/kg) was injected intraperitoneally 3 h after septic insult. Blood concentrations of soluble inflammatory mediators (interleukin [IL]-1β, IL-6, IL-10, and tumor necrosis factor [TNF]-α) were determined using a microarray immunoassay. Serum concentrations of HMG-B1 and syndecan-1, as a parameter of glycocalyx damage, were determined by enzyme-linked immunosorbent assay. The glycocalyx was also evaluated with electron microscopy. The lungs were removed, and digested to cells, which were then stained with a mixture of fluorophore-conjugated antibodies. Anti-mouse primary antibodies included PE-Cy7-conjugated anti-CD31, AlexaFluor 700-conjugated anti-CD45, PerCP-Cy5.5-conjugated anti-CD326, APC-conjugated anti-TNF-α, PE-conjugated anti-IL-6, and PE-conjugated anti-IL-10. A total of 1 × 10⁶ cells per sample were analyzed, and 2 × 10⁵ events were recorded by flow cytometry, and parameters were compared with/without rTM treatment.

RESULTS

The blood concentration of TNF-α was significantly reduced 24 h after intratracheal injection in S. pneumoniae-challenged mice treated with rTM (P = 0.016). Levels of IL-10 in the lung endothelium of rTM-treated S. pneumoniae-challenged mice increased significantly 12 h after intratracheal injection (P = 0.03). Intriguingly, serum HMGB-1 and syndecan-1 levels decreased significantly (P = 0.010 and 0.015, respectively) in rTM-treated mice 24 h after intratracheal injection of S. pneumoniae. Electron microscopy indicated that rTM treatment preserved the morphology of the glycocalyx layer in septic mice.

CONCLUSIONS

These data suggest that rTM modulates local inflammation in the lung endothelium, thus diminishing systemic inflammation, i.e., hypercytokinemia. Furthermore, rTM treatment reduced serum syndecan-1 levels, thus preventing glycocalyx damage. The use of rTM to treat sepsis caused by bacterial pneumonia could therefore help prevent both excessive inflammation and glycocalyx injury in the lung endothelium.

Pneumococcal serotype-specific IgG and opsonophagocytic activity in young Japanese patients with asplenia

Patients with asplenia are at high risks of severe infections caused by encapsulated bacteria, particularly Streptococcus pneumoniae. Thirteen-valent pneumococcal conjugate vaccine (PCV13) and 23-valent pneumococcal polysaccharide vaccine (PPSV23) are recommended for invasive pneumococcal disease prevention; however, little is known about the immunity to pneumococci in young patients with asplenia. We measured pneumococcal serotype-specific IgG (Pn-IgG) levels and pneumococcal opsonophagocytic activity (Pn-OPA) against some PCV13-contained serotypes (1, 3, 5, 6A, 7 F, 19A) in 23 young patients with asplenia using surplus serum samples. In this study, 5 and 13 patients had received PCV13 during routine immunizations and PPSV23, respectively; however, >5 years had passed since the last dose in most cases. The geometric mean concentrations (GMCs) of Pn-IgG in all study patients were not under the cutoff level against six serotypes, but they were lower than the those of age-matched healthy controls, as we have previously published. The patients who had received only PPSV23 had significantly lower GMCs against four serotypes (serotypes 1, 6A, 7 F, and 19A) than that of the patients who had received at least one PCV13 vaccination. The patients who had received only PPSV23 also had significantly lower geometric mean titers (GMTs) of Pn-OPA against all three serotypes we measured (serotypes 3, 5, and 19A) than that of the patients who had received at least one PCV13 vaccination. Our findings are useful data that can indicate insufficient immunity in young patients with asplenia against some PCV13 pneumococci serotypes and suggest the need for appropriate vaccinations in the post-PCV13 era.

A Double-Blind, Randomized, Placebo-Controlled Trial of Heat-Killed Pediococcus acidilactici K15 for Prevention of Respiratory Tract Infections among Preschool Children

Although some probiotic bacteria have been reported to prevent infections in children, there are few well-designed double-blind studies. Here we evaluated the effects of a probiotic strain of lactic acid bacteria (LAB), Pediococcus acidilactici K15, on viral respiratory tract infections in preschool children. A four-month, randomized, double-blind, placebo-controlled study was performed in 172 healthy children aged 3 to 6 years. Subjects were administered dextrin alone or dextrin including heat-killed K15 (5 × 10¹⁰ bacteria). The number of febrile days was the primary outcome. The number of absent days from preschools and the influenza incidence were secondary outcomes. Secretory IgA (sIgA) concentrations in saliva were measured as an exploratory outcome. The primary and secondary outcomes were not significantly different between both groups. Analyses in children with little intake of fermented foods including LAB showed that the duration of a fever significantly decreased by K15 intake. The salivary sIgA level in the K15 group was maintained significantly higher than it was in the placebo group. The effects of K15 on preventing viral respiratory tract infections were not observed without the restriction of fermented foods intake. However, K15 supported anti-infectious immune systems in children who took less fermented foods and the maintenance of salivary sIgA levels in all subjects.

First report on multidrug-resistant non-encapsulated Streptococcus pneumoniae isolated from a patient with pneumonia

The non-encapsulated Streptococcus pneumoniae (NESp) has emerged and increased in the clinical setting. The majority of NESp strains have been isolated from the nasopharynxes of healthy carriers and from respiratory specimens of patients with otitis media. NESp strains were shown to be more effective than encapsulated counterparts at forming biofilms. Therefore, NESp should become one of the leading causes of emerging refractory respiratory disease after the introduction of pneumococcal conjugate vaccines. We report the first case of multidrug-resistant - including fluoroquinolone-resistant - NESp isolated from the intrabronchial aspirate of a patient with pneumonia. Drug-resistant NESp infections can possibly emerge as a clinical problem and thus the continuous monitoring of NESp infections is of utmost importance.

Haemophilus influenzae type b capsular polysaccharide antibody levels in Japanese young patients with hematological malignancies and asplenia

Individuals with immunosuppressive condition have a high risk of invasive Haemophilus influenzae type b (Hib) infection. In Japan, routine Hib vaccination program for children under 5 years old was introduced in December 2008. However, the national policy does not make provision for individuals aged ≥5 years who have medical conditions associated with a high risk of invasive Hib disease to receive Hib vaccine. We measured serum anti-polyribosylribitol phosphate specific (anti-PRP) antibodies to Hib in patients aged ≥5 years with hematological malignancies and asplenia and evaluated their levels of anti-PRP antibodies in post administration of Hib vaccine era. A total of 65 patients (48 with hematological malignancies, and 17 with asplenia) were included in this study, of which 84% had not received Hib vaccine. In addition, 95.4% had short-term protective levels of anti-PRP antibodies (defined as ≥0.15 μg/mL) and 41.5% had long-term protective levels of anti-PRP antibodies (defined as ≥1.0 μg/mL). Five patients had low anti-PRP antibody levels despite a history of Hib vaccination. Our results suggest that young patients with underlying diseases such as hematological malignancies and asplenia may be at risk of invasive Hib disease. Hence, we recommend they should receive Hib vaccines even if they are over the age limit for routine Hib vaccination program.

The effects of health education on health science teachers' intention to recommend adolescent HPV vaccine for female students in Japan

The Japanese government suspended proactive recommendation of human papillomavirus (HPV) vaccination due to several reports of adverse events related to it in 2013. After that, the immunization rate of HPV vaccine quickly declined in Japan. Health science teachers (HSTs) are qualified and licensed teachers in charge of health care and health education for students in Japanese schools. HSTs have not recommended HPV vaccination to female students, since active governmental recommendation for HPV vaccination was halted for 5 y. We conducted a primary survey targeting HSTs (N = 39) and university students taking the HST training course (N = 123). In each group, awareness regarding HPV vaccine and disease burden was evaluated and factors related to and barriers to HPV vaccine recommendation were identified. The primary survey found that many HSTs and university students recognized their insufficient knowledge regarding the HPV vaccine. Based on the primary survey's results, infectious disease specialists, collaborating with Japanese HSTs, developed educational slide sets on HPV vaccine. A secondary survey was conducted before and after the lecture with HSTs (N = 162), where we evaluated their intelligibility and intention to recommend HPV vaccination for female students. In the post-lecture, secondary survey, the number of HSTs who recommended the HPV vaccine to their students had statistically increased from 76 before the lecture, to 103 (p < .05). An educational lecture using appropriate materials improved HSTs' vaccine confidence and intention to recommend the HPV vaccine to their students, verifying the study's hypothesis.

Psoitis and multiple venous thromboses caused by Panton Valentine Leukocidin-positive methicillin-sensitive Staphylococcus aureus in a 12-year-old girl: A case report

Panton Valentine Leukocidin (PVL) is one of the many toxins produced by Staphylococcus aureus. In Japan, PVL-positive S. aureus strains are mainly methicillin-resistant S. aureus (MRSA). Data regarding PVL-positive methicillin-sensitive S. aureus (MSSA) are scarce. In this report, we describe a case of severe infection by PVL-positive MSSA. A 12-year-old healthy girl was admitted with high fever and pain in the lower back. Computed tomography revealed a diagnosis of psoitis and multiple venous thromboses. Blood cultures obtained after admission revealed infection with MSSA. Her fever continued despite adequate antibiotic therapy. On the fifth hospitalization day, she developed bladder dysfunction, and an abscess was noted near the third lumbar vertebra. She underwent an emergency operation and recovered. Bacterial analyses revealed that the causative MSSA was a PVL-producing single variant of ST8 (related to USA300clone), of sequence type 2149. PVL is known to cause platelet activation. This case demonstrates the need for detailed analyses of the causative strain of bacteria in cases of S. aureus infection with deep vein thrombosis, even in cases of known MSSA infection.

Two pediatric cases of Pneumocystis jirovecii pneumonia diagnosed by polymerase chain reaction of gastric lavage

Detecting Pneumocystis jirovecii by bronchoalveolar lavage or lung biopsy is the gold standard for diagnosis of P. jirovecii pneumonia (PJP); however, these techniques are not always applicable in children because of their high invasiveness. We report two pediatric cases of PJP diagnosed by polymerase chain reaction (PCR) of gastric lavage that were successfully treated. To date, there are no reported cases of using PCR of gastric lavage to diagnose PJP. On the day of PJP onset, both the infants required respiratory support and infiltrative shadows were observed in both lung fields on chest radiography. Furthermore, their (1 → 3)-β-D glucan levels were elevated. P. jirovecii was detected by PCR of gastric lavage and trimethoprim-sulfamethoxazole was administered for 3 weeks, following which their condition improved. They were long-term steroid users, but without any prophylaxis. PCR of gastric lavage in cases of suspected PJP may help in confirming the diagnosis in children who have mild to moderate airway symptoms, or have difficulty with invasive examination like bronchoscopy.

Isolation Rate of Neisseria meningitidis in Japanese Children with Respiratory Tract Infections

Although invasive meningococcal disease is rare in Japan (0.028 cases per 100,000 population), its incidence is 10 times greater in many other countries. Colonization is a prerequisite for invasive meningococcal disease. However, no study in Japan has involved specifically analyzing the carriage rate of Neisseria meningitidis in children. During 5 months in 2015, the respiratory tract specimens of patients who presented to 3 hospitals with respiratory symptoms were cultured. The bacteria were identified in selective media using a meningococcal detection kit and the serogroup was identified using polymerase chain reaction analysis. In 389 patients aged ≤15 years with respiratory symptoms, the N. meningitidis isolation rate was 0.26% (1/389). The serogroup of the only child who tested positive was Y. In this study, we detected a low meningococcal isolation rate in pediatric patients. Due to increasing globalization, the risk of invasive meningococcal disease is likely increasing in Japan. Accordingly, invasive meningococcal diseases should be continuously monitored in Japan. Future large-scale studies should assess meningococcal isolation rates and corresponding serogroups.

Congenital Rubella Syndrome: A Case Report on Changes in Viral Load and Rubella Antibody Titers

To our knowledge, this is the first report of the use of real-time reverse transcription-polymerase chain reaction to assess changes in viral load in a patient with congenital rubella syndrome (CRS). Rubella-specific antibody titers were also determined. The patient was a male neonate born to a primipara with rubella infection at 10 weeks of gestation. He had no symptoms at birth, but rubella virus was detected in his pharynx, blood, and urine. His mental and physical development was normal for 1 year; however, he was diagnosed with deafness at 13 months of age. Thus, the patient was diagnosed with CRS. Rubella infection in the pharynx was almost constant until 5 months of age; however, it increased dramatically at 6 months of age. No infection was detected at 13 months. Rubella-specific immunoglobulin M titer was consistently low until 9 months of age and then decreased gradually until it became negative at 20 months of age. Rubella-specific immunoglobulin G titer was high at birth. However, it decreased at 3 months and increased again at 4 months. This titer peaked at ∼9 months and then decreased again at 13 months. This case shows that the period after the decline in maternal antibody titers, not the neonatal period, may be the most contagious period in patients with CRS.

[Comparison of the clinical effectiveness of three neuraminidase inhibitors for Japanese pediatric patients with influenza in the 2013/2014 season]

We investigated the clinical symptoms of 206 pediatric patients with influenza virus infection and compared them among oseltamivir-treated, zanamivir-treated, and laninamivir-treated groups in 2013/2014 influenza season. The drug compliance of each neuraminidase inhibitor was good in all three groups. Although the duration of fever after administration of the first dose of each neuraminidase inhibitor were significantly prolonged in the patient with influenza B infection than in the patient with influenza A infection, no statistically significant difference in the clinical efficacy and the side effect among three groups were found. The number of biphasic fever episodes in patients treated with neuraminidase inhibitor was rare (two episodes of oseltamivir-treated group and one episode of zanamivir-treated group). In conclusion, under the good drug compliance, the efficacy of all three neuraminidase inhibitor was the same for the treatment of influenza virus infection in children.

IgG levels against 13-valent pneumococcal conjugate vaccine serotypes in non pneumococcal conjugate vaccine immunized healthy Japanese and intravenous immunoglobulin preparations

No studies showed specific antibody levels against all serotypes covered by 13-valent pneumococcal conjugate vaccine (PCV13) among polyclonal intravenous immunoglobulin (IVIG) products. Our study aimed to assess whether we could expect the efficacy of IVIG therapy for invasive pneumococcal disease (IPD) and to clarify the age group which should be recommended for IVIG therapy in case of IPD. Serotype-specific immunoglobulin G (IgG) levels against PCV13 serotypes were measured in four IVIGs which were produced from Japanese donors who were not immunized with any pneumococcal conjugate vaccines (PCVs), and in the serum of 160 non-PCV immunized Japanese subjects, by enzyme-linked immunosorbent assay. The functional opsonic activities of the IVIGs against serotypes 6B and 19A were assessed by a multiplexed opsonophagocytic killing assay. Japanese infants aged <2 years had a geometric mean IgG concentration of <0.35 μg/ml against several serotypes. Serotype-specific IgG concentrations varied among IVIGs. In general, IgG antibodies against serotypes 6A, 14 and 19A were higher in each IVIG. Although opsonization indices also varied among preparations, each IVIG had the ability to opsonize both serotypes 6B and 19A. This study suggests that routine immunization with PCV is important for prevention of IPD, especially for children <2 years old and IVIGs might be effective for IPD patients.

Anterior Commissure Involvement in Humanherpes Virus 6 Encephalitis

The anterior commissure is an evolutionarily conserved nerve bundle that connects the right and left hemispheres, playing pivotal neurological roles in visual, linguistic, and olfactory functions. The authors herein describe a 16-month-old boy with high fever, lethargy, and recurrent seizures. Polymerase chain reaction (PCR) examination detected human herpesvirus 6 (HHV-6) in both the cerebrospinal fluid and the pharyngeal swabs, leading to the diagnosis of HHV-6 encephalitis. Brain magnetic resonance imaging (MRI) 4 days after disease onset distinctly revealed anterior commissure involvement on diffusion-weighted images and apparent diffusion coefficient maps, suggesting that this lesion was cytotoxic edema. After treatment with 30 mg/kg/d methylprednisolone for 3 days, the anterior commissure involvement on MRI was completely diminished. This is the first MRI report rarely showing anterior commissure involvement in encephalitis, suggesting that this lesion might be caused by direct invasion of HHV-6 or transient axonal swelling associated with inferior temporal lobe damage.

The incidence of pediatric invasive Haemophilus influenzae and pneumococcal disease in Chiba prefecture, Japan before and after the introduction of conjugate vaccines

The Haemophilus influenzae type b (Hib) vaccine and the heptavalent pneumococcal conjugate vaccine (PCV7) were introduced in Japan in 2008 and 2010, respectively. In 2011, immunization with these two vaccines was encouraged throughout Japan through a governmental program. Children treated in Chiba prefecture for culture-proven invasive H. influenzae disease (IHiD) and invasive Streptococcus pneumoniae disease (IPD) were identified in a prefectural surveillance study from 2008 to 2013. The incidence rate ratio (IRR) and its confidence interval (CI) were calculated to compare the 3 years before and after governmental financial support for vaccination. The average number of IHiD and IPD cases among children <5 years of age in 2011-2013 decreased 84% (IRR: 0.16, 95% CI: 0.09-0.26, p<0.0001) and 51% (IRR: 0.49, 95% CI: 0.37-0.63, p<0.0001) compared with those occurring in 2008-2010. The most common non-PCV7 serotype encountered in 2011 and 2013 was 19A. After governmental subsidization of Hib and PCV7 vaccination, IHiD and IPD decreased in Chiba prefecture, Japan. Continuous surveillance is necessary to determine the effectiveness of these two vaccines and for detection of emerging invasive serotypes.

Streptococcus gallolyticus subsp. pasteurianus meningitis in an infant

Streptococcus gallolyticus subsp. pasteurianus was formerly classified as S. bovis biotype II/2, which is recognized as a rare cause of neonatal sepsis and meningitis. Since the taxonomy classification change, there have not been many reports of meningitis due to S. gallolyticus subsp. pasteurianus. Moreover, the pathogenesis of late onset S. gallolyticus subsp. pasteurianus meningitis in infants is unclear. Here we report a case of meningitis in a 5-week-old infant with preceding diarrhea. S. bovis biotype II/2 was isolated from the blood, cerebrospinal fluid and stool, and then was identified as S. gallolyticus subsp. pasteurianus on 16S rRNA gene sequencing. Isolates from all three sample types had identical profiles on pulsed-field gel electrophoresis. The intestinal tract was thought to be the source of the infection.

Changes in nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis among healthy children attending a day-care centre before and after official financial support for the 7-valent pneumococcal conjugate vaccine and H. influenzae type b vaccine in Japan

The 7-valent pneumococcal conjugate vaccine (PCV7) and Haemophilus influenzae type b (Hib) vaccine reduce nasopharyngeal carriage of vaccine-type bacteria, which may in turn influence the presence of other nasopharyngeal bacterial pathogens. To investigate this possibility, nasopharyngeal carriage of potential pathogens was examined before and after official financial support was provided to offer the PCV7 and Hib vaccines in healthy children attending a day care centre in Japan during 2011-2012. Despite a virtual disappearance of PCV7 serotypes over time, the overall pneumococcal carriage rate remained unchanged. Although others have reported an increase in PCV13 serotypes following PCV7 vaccination, only non-PCV13 serotypes were observed to have increased in this study. The majority of H. influenzae isolates were non-typeable and Hib was not found. Our data identified an unexpected pattern of pneumococcal serotype replacement following PCV7. Continuous monitoring of pneumococcal carriage is important for decisions regarding the future of national vaccination policy in Japan.

Isoniazid- and streptomycin-resistant miliary tuberculosis complicated by intracranial tuberculoma in a Japanese infant

In Japan, the incidence of severe pediatric tuberculosis (TB) has decreased dramatically in recent years. However, children in Japan can still have considerable opportunities to contract TB infection from adult TB patients living nearby, and infants infected with TB may develop severe disseminated disease. A 3-month-old girl was admitted to our hospital with dyspnea and poor feeding. After admission, miliary TB and multiple brain tuberculomas were diagnosed. Anti-tuberculous therapy was initiated with streptomycin (SM), isoniazid (INH), rifampicin and pyrazinamide. Symptoms persisted after starting the initial treatment and mycobacterial cultures of gastric fluid remained positive. Drug sensitivity testing revealed the TB strain isolated on admission as completely resistant to INH and SM. Treatments with INH and SM were therefore stopped, and treatment with ethambutol and ethionamide was started in addition to rifampicin and pyrazinamide. After this change to the treatment regimen, symptoms and laboratory data gradually improved. The patient was treated with these four drugs for 18 months, and then pyrazinamide was stopped. After another 2 months, ethambutol was stopped. Treatment of tuberculosis was completed in 24 months. No adverse effects of these anti-TB drugs were observed. The patient achieved a full recovery without any sequelae. On the other hand, the infectious source for this patient remained unidentified, despite the extensive contact investigations. The incidence of drug-resistant TB is increasing in many areas of the world. Continuous monitoring for pediatric patients with drug-resistant TB is therefore needed.

A case of meningoencephalitis associated with macrolide-resistant Mycoplasma pneumoniae infection

Mycoplasma pneumoniae, a common pathogen causing community-acquired pneumonia, is also known to cause meningoencephalitis in pediatric patients. We report herein a pediatric patient with meningoencephalitis and macrolide-resistant M. pneumoniae infection. We emphasize that macrolide-resistant M. pneumoniae must be taken into consideration in patients with encephalitis, along with consideration for using minocycline even in pediatric patients.

Rhabdomyolysis associated with influenza A/H1N1 2009 infection in a pediatric patient

The influenza A/H1N1 2009 epidemic has spread to many countries since 2009, including Japan. We report an immune-competent child involving rhabdomyolysis and compartment syndrome associated with influenza A/H1N1 2009. The patient was demonstrated rhabdomyolysis with myoglobinuria, hyperkalemia, cardiac dysfunction and compartment syndrome that arose during convalescence from influenza A/H1N1 2009 infection. Although RT-PCR of muscle tissue yielded negative results for influenza A/H1N1 2009 RNA and no viral positive-antigen cells were detected in the muscle lesions, the clinical picture suggested rhabdomyolysis associated with influenza A/H1N1. Rhabdomyolysis should be considered in the evaluation of muscle symptoms such as myalgia associated with novel influenza A/H1N1 2009 virus infection, particularly in critically ill patients.

Anti-polyribosylribitol phosphate antibody in pediatric patients with Haemophilus influenzae type b invasive disease

Haemophilus influenzae type b conjugate vaccine was recently introduced to Japan for voluntary immunizations. H. influenzae type b remains a leading cause of pediatric invasive diseases in Japan. The purposes of this study were to verify the suitability of the H. influenzae type b conjugate vaccine for immunizing children with a history of invasive H. influenzae type b disease and to determine whether H. influenzae type b conjugate vaccine is immunogenic in these children. The subjects comprised 64 children with a history of invasive H. influenzae type b disease. Serum samples from 64 patients with H. influenzae type b systemic infection in the acute and convalescent phases were analyzed. Serum anti-polyribosylribitol phosphate antibody responses of patients < 2 years old were poorer than those observed in patients ≥ 2 years old. Nineteen of the 64 patients received a single dose of H. influenzae serotype b conjugate vaccine, and then follow-up serum was taken and analyzed. Eighteen of 19 patients had ≥ 1 μg/mL of anti-polyribosylribitol phosphate antibody titer after the first dose of H. influenzae type b conjugate vaccine. H. influenzae type b conjugate vaccine is immunogenic in children with invasive H. influenzae type b disease. Children < 4 years old, and particularly < 2 years old, with invasive H. influenzae type b disease should receive subsequent immunization with a H. influenzae type b conjugate vaccine.

The effects of disodium cromoglycate on enhanced adherence of Haemophilus influenzae to A549 cells infected with respiratory syncytial virus

Nontypeable Haemophilus influenzae (NTHi) secondary infection often complicates respiratory syncytial virus (RSV) infections. Previous studies have revealed that RSV infections enhance NTHi adherence to airway epithelial cells. In this study, we investigated the effects of disodium cromoglycate (DSCG) and corticosteroids, which are frequently used for the treatment of wheezing often related to RSV infections, on the adherence of NTHi to RSV-infected A549 cells. DSCG inhibited enhanced adherence of NTHi to RSV-infected A549 cells, whereas dexamethasone (Dex) and fluticasone propionate (Fp) did not. DSCG suppressed the expression of ICAM-1, which is one of the NTHi receptors. Furthermore, DSCG exhibited an inhibitory effect on RSV infections. It is suggested that DSCG exerts an anti-RSV effect, and consequently attenuates the expression of NTHi receptors.

Quantitative measurements of Hemophilus influenzae type b capsular polysaccharide antibodies in Japanese children

BACKGROUND

Hemophilus influenzae type b (Hib) infection has a high morbidity and mortality rate in children. The frequency of natural immunity against Hib in Japanese children is not known, and Hib vaccine has not yet been introduced in Japan.

METHODS

Anti-capsular polysaccharide-specific IgG (anti-CP) antibody titers were examined in serum samples from 100 children and 107 young adults who were not vaccinated against Hib, in serum samples from eight patients with Hib systemic infection and in 10 commercially available human immune globulin preparations on enzyme-linked immunosorbent assay.

RESULTS

A total of 44% (44/100) of Japanese children and all patients with Hib systemic infection in the acute phase did not have the minimum protective level of anti-CP antibodies (>0.15 microg/mL). The rate of natural Hib immunity was lowest in children under 1 year of age and gradually increased with age. Only 3.74% (4/107) of Japanese young adults did not have the minimum protective level of anti-CP antibodies. Analysis of 10 commercially available human immune globulin preparations indicated an average level of 28.25 microg anti-CP antibody/mL immune globulin (range 14.96-44.17 microg/mL).

CONCLUSIONS

Approximately half of Japanese children are not protected against Hib infection. Therefore, Hib vaccine should immediately be included as part of the routine immunization program in Japan. It was also found that all tested commercially available immune globulin preparations had high anti-CP titers. Well-controlled clinical trials of i.v. immune globulin administration for prevention and treatment of Hib systemic infection are needed in Japan.

[Studies of treatment for Haemophilus influenzae type b meningitis in children]

We summarize 41 cases of bacterial meningitis in the last 11 years caused by Haemophilus influenzae. All isolates were serotype b strain (Hib). Initial chemotherapy was started with ceftriaxone (CTRX) in 22 cases, ampicillin plus cefotaxime (CTX) in 9, CTRX plus panipenem/betamipron in 5, and CTX in 2. Some 31 cases were treated mainly with CTRX. Although therapeutic antibiotics showed good susceptibility for isolates, 8 complicated cases (19.5%) occurred. Sequalae were observed in 7 (17.1%) but none were fatal. Five strains with elevated MIC of CTX (0.12 to 1 microg/mL) recovered after 2001, and 3 of 5 strains also showed elevated MIC of CTRX (0.12 to 0.5 microg/mL), but all were cured completely with CTRX. At present, no treatment failures due to antibiotic resistance have been observed, and CTRX remains suitable as initial therapy for Hib meningitis. A decline in susceptibility for third-generation cephalosporin against beta-lactamase-nonproducing ampicillin-resistant H. influenzae is emerging, however, so it will be necessary to consider combination therapy with CTRX given the foreseeable trend in MICs.

[Clinical effects of piperacillin and tazobactam/piperacillin on Haemophilus influenzae lower respiratory tract infection in pediatric patients]

OBJECTIVE

The prevalence of beta-lactamase-nonproducing ampicillin-resistant (BLNAR) Haemophilus influenzae (H. influenzae) has been increasing in recent years. Piperacillin (PIPC) is one of a few beta-lactams possessing good activity against BLNAR H. influenzae. We studied clinical efficacy of piperacillin and its beta-lactamase inhibitor, tazobactam/piperacillin (TAZ/PIPC) in children with lower respiratory tract infection caused by H. influenzae including resistance strains.

METHODS

Subjects were 20 children with lower respiratory tract infection caused by H. influenzae treated with PIPC 100mg/kg/day (7 cases) or TAZ/PIPC 125mg/kg/day (13 cases). We selected cases from which resistant H. influenzae strains might be detected. Patients received prior antimicrobial therapy within two weeks before admission, or with underlying diseases. We examined patient profiles, clinical efficacy, susceptibilities for 6 beta-lactam antibiotics [PIPC, TAZ/PIPC, ampicillin (ABPC), cefotaxime (CTX), ceftriaxone (CTRX), and meropenem (MEPM)] and analyzed 6 genotype patterns of beta-lactam resistant genes by PCR.

RESULTS

Efficacy was 7/7 in patients in PIPC group and 12/13 in patients in TAZ/PIPC group. Diminished efficacy was seen in only one case complicated with severe RSV infection. The susceptibility of all strains but one beta-lactamase producing, ABPC resistant (BLP) strain to PIPC and of all to TAZ/ PIPC was below 0.25 microg/mL. The genotype of the 15 strains isolated from the sputum on administration was as follows; beta-lactamase nonproducing, ABPC-susceptible (gBLNAS) strains were 4, gBLP strain was 1, beta-lactamase nonproducing, and ABPC-resistant (gLow-BLNAR) strains were 2, beta-lactamase nonproducing, ABPC resistant (gBLNAR) strains were 8.

CONCLUSION

PIPC and TAZ/PIPC were useful against lower respiratory tract infection caused by H. influenzae including BLNAR in children.

Induction of mucosal B-cell memory by intranasal immunization of mice with respiratory syncytial virus

The capacity of live or inactivated respiratory syncytial virus (RSV) to induce B-cell memory in respiratory-associated lymphoid tissues of mice was examined. Eight weeks after primary inoculation with either live or inactivated RSV, adult BALB/c mice were challenged with 4x10(5) PFU of RSV. Protection from viral shedding and mucosal production of RSV-specific antibodies were examined at various time points after challenge. We found that primary immunization with live, but not inactivated, RSV induced complete and durable protection upon challenge within the upper and lower respiratory tract. Also, primary immunization with live, but not inactivated, RSV enhanced the production of mucosal RSV-specific immunoglobulin A (IgA) upon challenge. Secondary mucosal IgA responses were characterized by (i) the early production of mucosal IgA by B cells that reside in organized nasal-associated lymphoid tissues, cervical lymph nodes, and bronchial lymph nodes, and (ii) the subsequent production of RSV-specific IgA by mucosal effector tissues, such as the tracheal lamina propria and lung. These findings suggest that primary infection of mice with live RSV might induce mucosal IgA-committed memory B cells. A greater understanding of the characteristics of RSA-specific mucosal memory B cells may facilitate the development of an RSV vaccine.

Regional differences in the early mucosal immune response induced by primary inoculation of mice with respiratory syncytial virus

Respiratory syncytial virus (RSV) is the most important cause of respiratory tract infection in infants. Little is known about the characteristics of critical immunologic inductive sites within respiratory-associated lymphoid tissues (RALT) upon RSV infection. We examined the kinetics and characteristics of early mucosal RSV-specific immune responses after primary inoculation of mice. We found that the initial production of virus-specific antibodies was restricted to the organized lymphoid tissues of RALT, such as nasal-associated lymphoid tissue (NALT), cervical and bronchial lymph nodes (CLN and BLN). In addition, virus-specific IgM was produced by B cells resident in CLN and BLN, but not NALT, of mice. Finally, we observed regional differences in the pattern of RSV-specific antibodies produced by RALT; B cells within NALT and CLN produced equivalent quantities of virus-specific IgG2a and IgG2b. However, an IgG2a response predominated in BLN. Together these data demonstrate regional differences in the early mucosal immune response to RSV. Further understanding of these differences may assist the development of RSV vaccines.

Acute encephalopathy associated with nontyphoidal salmonellosis

The importance of an acute encephalopathy associated with nontyphoidal salmonellosis has recently been recognized, but the disease entity has been poorly established. In this study, we describe two encephalopathic patients associated with nontyphoidal salmonellosis. The patients exhibited a rapid evolution of coma after the onset of lethargy or seizure. Fever and diarrhea due to salmonellosis preceded these events. Secondary factors inducing encephalopathies, such as severe dehydration, sepsis, meningitis, electrolyte or metabolic disturbances, acute renal failure, and multiple organ failure, were excluded in the differential diagnosis at the onset of encephalopathic features. These clinical findings and rapid development of encephalopathic features from localized intestinal infection without any significant abnormalities in a variety of blood tests may suggest a toxic etiology. However, endotoxin was not found in serum from both patients. From these results, we conclude that nontyphoidal salmonellosis can cause a toxic encephalopathy syndrome, like shigellosis or verocytotoxin-producing Escherichia coli infection.