Invasive Haemophilus influenzae disease among adults in Japan during 2014-2018.

PURPOSE: We describe the epidemiology of invasive Haemophilus influenzae disease (IHD) among adults in Japan. METHODS: Data for 200 adult IHD patients in 2014-2018 were analyzed. The capsular type of H. influenzae was determined by bacterial agglutination and polymerase chain reaction (PCR), and non-typeable Haemophilus influenzae (NTHi) was identified by PCR. RESULTS: The annual incidence of IHD (cases per 100,000 population) was 0.12 for age 15-64 years and 0.88 for age ≥ 65 years in 2018. The median age was 77 years, and 73.5% were aged ≥ 65 years. About one-fourth of patients were associated with immunocompromising condition. The major presentations were pneumonia, followed by bacteremia, meningitis and other than pneumonia or meningitis (other diseases). The case fatality rate (CFR) was 21.2% for all cases, and was significantly higher in the ≥ 65-year group (26.1%) than in the 15-64-year group (7.5%) (p = 0.013). The percentage of cases with pneumonia was significantly higher in the ≥ 65-year group than in the 15-64-year group (p < 0.001). The percentage of cases with bacteremia was significantly higher in the 15-64-year group than in the ≥ 65-year group (p = 0.027). Of 200 isolates, 190 (95.0%) were NTHi strains, and the other strains were encapsulated strains. 71 (35.5%) were resistant to ampicillin, but all were susceptible to ceftriaxone. CONCLUSION: The clinical presentations of adult IHD patients varied widely; about three-fourths of patients were age ≥ 65 years and their CFR was high. Our findings support preventing strategies for IHD among older adults, including the development of NTHi vaccine.

Case report: pulmonary nocardiosis caused by Nocardia exalbida in an immunocompetent patient.

BACKGROUND: Nocardiosis is known as an opportunistic infection in immunocompromised hosts, but it occasionally has been reported in immunocompetent patient. The Nocardia exalbida is first-reported in 2006 from Japan, and a few cases of have been reported in only immunocompromised host, and the characteristic is still unclear. We herein describe the first case of pulmonary nocardiosis caused by N. exalbida in an immunocompetent patient. CASE PRESENTATION: A77 -year-old Japanese man was admitted to our hospital on November 2, 2018. He was a lifelong non-smoker with no childhood history of respiratory disease. He had a medical history of dyslipidemia. One month before this admission fevers, sputum, mild cough were developed and he was evaluated in a clinic near our hospital. His diagnosis was community acquired pneumonia within his right middle lobe. He was treated with ceftriaxone 1 g/day intravenously for a week, however his symptoms relapsed a few days later. So, the physician retried ceftriaxone for another 3 days, but his symptoms did not improve. He was referred to our hospital. He was treated with sitafloxacin as an outpatient for a week, however his symptoms got worse. The chest CT showed consolidation and atelectasis in his right middle lobe. Low density area was scattered in consolidation, and right pleural effusion was observed. The patient was diagnosed with pulmonary abscess and he was admitted. Administration of piperacillin/tazobactam improved his condition. We switched antibiotics to amoxicillin/clavulanate, and he was discharged. After 2 weeks, he relapsed and was admitted again. After administration of piperacillin/tazobactam for 3 weeks, we perform bronchoscopy and Nocardia species were cultured from samples of the bronchial wash. The isolates were identified as N. exalbida using 16S rRNA gene sequencing. We prescribed Trimethoprim / Sulfamethoxazole (TMP/SMX) for 4 months. Then we switched to minocycline for renal dysfunction caused from TMP-SMX for 1 more month. After 5 months therapy, Consolidation on CT disappeared, and Nocardiosis was cured. CONCLUSION: we reported the first case of pulmonary nocardiosis caused by N. exalbida in an immunocompetent patient. N. exalbida infection might be associated with a good response to treatment.

Relationship between detection of hepatitis B virus in saliva and periodontal disease in hepatitis B virus carriers in Japan.

INTRODUCTION: Although hepatitis B virus infection is well-described, the additional risk posed by oral bleeding in individuals with chronic hepatitis B virus infection has not been determined. This study aimed to determine the quantity of hepatitis B virus in the saliva of carriers in Japan, as a means of understanding the potential risk for horizontal transmission. METHODS: Saliva samples from 48 confirmed hepatitis B virus carriers were included in the analysis. Hepatitis B virus concentrations and the presence of occult blood as periodontal disease were evaluated in each sample. RESULTS: Hepatitis B surface antigen was identified in 46 of the 48 samples (98%), with hepatitis B virus DNA identified in 19 of the 48 saliva samples (40%). Occult blood was detected in 32 (67%) samples with the prevalence increasing as a function of age (r = 0.413; P = 0.003). There was a significantly positive correlation between hepatitis B virus DNA levels in the serum and saliva specimens (r = 0.895; P < 0.001). CONCLUSIONS: Occult blood in saliva was detected in most participants. The detection of hepatitis B virus DNA correlated positively with hepatitis B virus in the serum and occult blood in the saliva. Therefore, improved care of periodontal disease among older people is important for preventing horizontal transmission of hepatitis B virus.

Effectiveness of 23-Valent Pneumococcal Polysaccharide Vaccine against Invasive Pneumococcal Disease in Adults, Japan, 2013-2017.

The decline in the proportion of pneumococcal conjugate vaccine (PCV)-covered serotypes among adult invasive pneumococcal disease (IPD) patients might change the overall effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPSV23) because its effectiveness differs according to serotype. Using the indirect cohort method, we calculated the effectiveness of PPSV23 against IPD among adults in Japan to assess the impact of the national pediatric PCV program. Clinical and epidemiologic information and pneumococcal isolates were collected from IPD patients >20 years of age through enhanced IPD surveillance during April 2013-December 2017. Adjusted effectiveness against PPSV23-serotype IPD was 42.2%. Despite a substantial decline in the proportion of 13-valent PCV serotypes during the study period (45% to 31%), the change in effectiveness for PPSV23-serotype IPD was limited (47.1% to 39.3%) and only marginal in the elderly population (39.9% to 39.4%). The pediatric PCV program had limited impact on PPSV23 effectiveness against IPD in adults.

Serum Anti-interferon-γ Autoantibody Titer as a Potential Biomarker of Disseminated Non-tuberculous Mycobacterial Infection.

PURPOSE: In the past decade, the relationship between naturally occurring interferon-γ-neutralizing autoantibodies (IFNγ-Ab) and disseminated non-tuberculous mycobacteria (NTM) infection has been established. Furthermore, immune suppressive therapy aimed at the suppression of antibody production has shown efficacy as a supportive treatment. However, the nature of antibody behavior and antibody titer during the course of this disease, as well as the pathophysiological significance of IFNγ-Ab, has not yet been fully elucidated. METHODS: Thirteen Japanese subjects suffering from disseminated NTM (dNTM) infection with IFNγ-Ab were evaluated. The fluctuation of IFNγ-Ab titer and the neutralizing capacity against IFN-γ during the course of the disease were retrospectively analyzed. IFNγ-Ab titers in the sera were quantified using an enzyme-linked immunosorbent assay; neutralizing capacity was evaluated via flow cytometry. RESULTS: Serum antibody titers were not constant during the treatment period and varied over the course of the disease. The antibody titer decreased when the disease was improved by anti-mycobacterial treatment (p < 0.01) and increased as the disease progressed (p < 0.05). Even after the antibody titer decreased, the neutralizing capacity against IFN-γ was maintained by individual sera. CONCLUSIONS: Despite the improvement in the pathological condition via treatment, the patients' sera maintained neutralizing capacity against IFN-γ. Antibody titer fluctuated over the course of the disease and exhibited potential as a biomarker for judgment of the disease state.

Essential human resources for antimicrobial stewardship teams in Japan: Estimates from a nationwide survey conducted by the Japanese Society of Chemotherapy.

Implementation of antimicrobial stewardship programs (ASPs) with multidisciplinary antimicrobial stewardship teams (ASTs) is critical for appropriate antimicrobial use at healthcare facilities. Although the Japanese medical reimbursement system was revised to allow fees for ASP implementation, several concerns remain, including understaffing and enforcement of the recommendations on ASTs and ASPs in practice. Furthermore, there are no recommendations on full-time equivalents (FTEs) of the core members in ASTs in Japan. This committee report presents our recommendations on ASTs based on an analysis of the nationwide survey on implemented ASPs and staff FTEs at 1358 healthcare facilities conducted by the Japanese Society of Chemotherapy. Our report provides a directive for structural and financial support of ASTs and should aid in planning for the enhancement of AST practices and the organization of new ASTs.

Clinical Significance of Interferon-γ Neutralizing Autoantibodies Against Disseminated Nontuberculous Mycobacterial Disease.

Background: Interferon-γ neutralizing autoantibodies (nIFNγ-autoAbs) are reported in patients with disseminated nontuberculous mycobacteria (NTM) infection and may function by increasing the infection risk. Notwithstanding, the prevalence of nIFNγ-autoAbs as well as the clinical presentation, diagnosis, and natural history of disseminated NTM infection in these patients is poorly understood. Methods: In this retrospective observational study, data and sera for 331 Japanese subjects with mycobacterial infection were collected and analyzed. IFNγ-autoAb titers in sera were quantified using an enzyme-linked immunosorbent assay; neutralizing capacity was evaluated via flow cytometry. Results: Disseminated NTM was identified in 50 human immunodeficiency virus-uninfected patients. Of these, 30 of 37 (81%) immunocompetent patients had an increased nIFNγ-autoAb titer whereas only 1 of 13 (7.7%) immunodeficient patients had an increased nIFNγ-autoAb titer (P < .0001, χ2 test). Presenting symptoms were nonspecific and NTM infection was not included in the differential diagnosis in most cases. All patients with disseminated NTM and an increased serum nIFNγ-autoAb level received prolonged antimicrobial therapy. In 6 cases when antibiotic treatment was discontinued, NTM infection recurred and required resumption of antibiotic therapy for infection control. The mortality rate was 3.2% in disseminated NTM patients with nIFNγ-autoAbs and 21% in those without. Conclusions: nIFNγ-autoAbs were present in most patients with disseminated NTM infection without a diagnosis of clinical immunodeficiency. Diagnosis of disseminated NTM requires a high degree of suspicion and can be improved by measuring serum nIFNγ-autoAb titer. Long-term antibiotic therapy helps prevent recrudescent NTM infection.

Megalin Blockade with Cilastatin Suppresses Drug-Induced Nephrotoxicity.

Nephrotoxicity induced by antimicrobial or anticancer drugs is a serious clinical problem. Megalin, an endocytic receptor expressed at the apical membranes of proximal tubules, mediates the nephrotoxicity of aminoglycosides and colistin, key antimicrobials for multidrug-resistant organisms. The mechanisms underlying the nephrotoxicity induced by vancomycin, an antimicrobial for methicillin-resistant Staphylococcus aureus, and cisplatin, an important anticancer drug, are unknown, although the nephrotoxicity of these drugs and gentamicin, an aminoglycoside, is suppressed experimentally with cilastatin. In the clinical setting, cilastatin has been used safely to suppress dehydropeptidase-I-mediated renal metabolism of imipenem, a carbapenem antimicrobial, and thereby limit tubular injury. Here, we tested the hypothesis that cilastatin also blocks megalin-mediated uptake of vancomycin, cisplatin, colistin, and aminoglycosides, thereby limiting the nephrotoxicity of these drugs. Quartz crystal microbalance analysis showed that megalin also binds vancomycin and cisplatin and that cilastatin competes with megalin for binding to gentamicin, colistin, vancomycin, and cisplatin. In kidney-specific mosaic megalin knockout mice treated with colistin, vancomycin, or cisplatin, the megalin-replete proximal tubule epithelial cells exhibited signs of injury, whereas the megalin-deficient cells did not. Furthermore, concomitant cilastatin administration suppressed colistin-induced nephrotoxicity in C57BL/6J mice. Notably, cilastatin did not inhibit the antibacterial activity of gentamicin, colistin, or vancomycin in vitro, just as cilastatin did not affect the anticancer activity of cisplatin in previous studies. In conclusion, megalin blockade with cilastatin efficiently suppresses the nephrotoxicity induced by gentamicin, colistin, vancomycin, or cisplatin. Cilastatin may be a promising agent for inhibiting various forms of drug-induced nephrotoxicity mediated via megalin in the clinical setting.

Community- and hospital-acquired infections with oseltamivir- and peramivir-resistant influenza A(H1N1)pdm09 viruses during the 2015-2016 season in Japan.

We report five cases of community- and hospital-acquired infections with oseltamivir- and peramivir-resistant A(H1N1)pdm09 viruses possessing the neuraminidase (NA) H275Y mutation during January-February 2016 in Japan. One case was hospitalized and was receiving oseltamivir for prophylaxis. The remaining four cases were not taking antiviral drugs at the time of sampling. These cases were geographically distant and epidemiologically unrelated. The five viruses showed ~300-fold rise in IC50 values against oseltamivir and peramivir, defined as highly reduced inhibition according to the WHO definition. Overall, the prevalence of the H275Y A(H1N1)pdm09 viruses was 1.8 % (5/282). The resistant viruses possessed the V241I, N369 K, and N386 K substitutions in the NA that have been previously reported among A(H1N1)pdm09 to alter transmission fitness. Analysis of Michaelis constant (Km) revealed that two of the isolates had reduced NA affinity to MUNANA, while the other three isolates displayed a slightly decreased affinity compared to the sensitive viruses. Further studies are needed to monitor the community spread of resistant viruses and to assess their transmissibility.

Invasive pneumococcal disease among adults in Japan, April 2013 to March 2015: disease characteristics and serotype distribution.

BACKGROUND: In Japan, the clinical characteristics and recent serotype distribution among adult patients of invasive pneumococcal disease (IPD) have not been fully investigated since the introduction of the pneumococcal conjugate vaccine (PCV) in children. From November 2010, PCV7 was encouraged by an official program, funded by government, subsequently included in the routine schedule in April 2013, and replaced with a PCV13 in November 2013. METHODS: Between April 2013 and March 2015, patients with IPD older than 15 years were evaluated based on the enhanced national surveillance in ten prefectures of Japan. The serotype distribution of the isolates was analyzed in these patients. RESULTS: The analysis included 291 patients: 107 patients (37%) were female and the median age was 70 years. Of 281 patients with available data, 202 (72%) had underlying diseases, including 107 patients (38%) with immunocompromised status. The case fatality proportion for all case was 20%. In subgroup analysis, the case fatality proportion (29%) in immunocompromised patients was much higher than that (0-16%) in each age group of nonimmunocompromised patients (15-39 years, 40-64 years, and ≥ 65 years). While the proportion of bacteremia without any focus (27%) was higher than that (8-10%) in nonimmunocompromised patients, the proportions of vaccine types (PCV13, 32%; PPSV23, 51%) of the causative isolates were lower than those in each age group of nonimmunocompromised patients. Among 291 isolates, the most frequent serotypes were 3 (17%), 19A (13%), and 22F (10%). Twelve percent of the isolates were PCV7 serotypes, 46% were PCV13 serotypes, and 66% were PPSV23 serotypes. CONCLUSIONS: The majority of adult patients of IPD had underlying diseases, including immunocompromised conditions. A low proportion (12%) of PCV7-type IPD was observed in this population where PCV7 for children had been included in the routine immunization schedule.

Plasma and saliva concentrations of abacavir, tenofovir, darunavir, and raltegravir in HIV-1-infected patients
.

OBJECTIVE: We studied the relationships between plasma and saliva concentrations of antiretroviral drugs to explore whether saliva can be used for therapeutic drug monitoring (TDM). METHODS: Abacavir (ABC), tenofovir (TFV), darunavir (DRV), and raltegravir (RAL) in plasma and saliva from 30 HIV-1-infected patients were quantified using liquid chromatography-tandem mass spectrometry. RESULTS: Mean saliva-to-plasma concentration ratios were 0.623 (ABC), 0.024 (TFV), 0.065 (DRV), and 0.0135 (RAL), which agree with the plasma protein binding rates except TFV. Significant correlations were evident between saliva and plasma concentrations of ABC, DRV, and RAL. CONCLUSIONS: This study suggests that plasma concentrations of ABC, DRV, and RAL can be estimated from their saliva concentrations and that the saliva concentration of some antiretroviral drugs reflects the unbound drug concentration in plasma.
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A-DROP system for prognostication of NHCAP inpatients.

Nursing and healthcare-associated pneumonia (NHCAP) is a category of healthcare-associated pneumonia that was modified for the healthcare system of Japan. The NHCAP guidelines stated the difficulty in assessing the severity classifications, for instance, A-DROP. We compared the usefulness of different severity classifications (A-DROP, CURB-65, PSI, and I-ROAD) in predicting the prognosis of nursing and healthcare-associated pneumonia. We conducted a retrospective analysis on 303 adult patients hospitalized for nursing healthcare-associated pneumonia and community-acquired pneumonia, which were diagnosed at the Department of Respiratory Medicine of Niigata General City Hospital between January 2012 and December 2014. We evaluated 159 patients with community-acquired pneumonia and 144 with nursing and healthcare-associated pneumonia. In the nursing and healthcare-associated pneumonia group, 30-days mortality and in-hospital mortality rates were 6.5% and 8.7%, respectively, in severe cases and 16.1% and 25.0%, respectively, in the most severe cases, based on A-DROP. With I-ROAD, these rates were 11.1% and 11.1%, respectively, in group B and 14.9% and 20.7%, respectively, in group C. With PSI, the rates were 2.3% and 6.8%, respectively, in class IV and 14.3% and 19.8%, respectively, in class V. Despite some variability due to the small sample size, both the 30-days and in-hospital mortality rates increased as the severity increased. In this study, both the 30-days mortality and in-hospital mortality rates in the nursing and healthcare-associated pneumonia group tended to increase in severity with the A-DROP. We found that A-DROP was useful in predicting the prognosis of nursing and healthcare-associated pneumonia.

[The Effect of Intravenous Gamma-globulin Reagents on the Measurement Results of (1➔3)-ß-D-glucan].

Serum (1→3) beta-D-glucan (BG) measurement is a useful test for systemic mycoses, and often used. On the other hand, various factors, including administration of intravenous immunoglobulins (IVIG) may cause false-positives. In the present study, we measured BG concentration of seven IVIG preparations with three lots respectively. BG levels varied with individual IVIG preparations (<3.0 - >300 pg/mL), and contamination from manufacturing processes was suspected. With serum BG concentration of clinical specimens obtained in Niigata University Medical & Dental Hospital, the difference between before and after administration of IVIG were calculated. The false-positive rate of BG due to IVIG administration was 9.8 %, and the positive predective value was reduced to 37.5%. Above all, administration of IVIG can complicate the BG test's interpretation, and caution is required.

Novel assay to detect increased level of neutralizing anti-interferon gamma autoantibodies in non-tuberculous mycobacterial patients.

Subjects exposed to non-tuberculous mycobacterium (NTM) species do not always develop an active disease, which likely reflects underlying host susceptibility factors. Recent reports have shown that anti interferon gamma (IFN-γ) neutralizing autoantibodies (IFN-γ Ab) are associated with the development of disseminated NTM in patients without known evidence of immunodeficiency. The purpose of this study is to establish the screening method if subjects have IFN-γ Ab. Whole blood was obtained from patients with disseminated NTM, those with pulmonary NTM, and healthy controls. The neutralizing capacity to IFN-γ activity was assessed as an inhibition of Signal Transducer and Activation of Transcription 1 (STAT-1) phosphorylation in leukocyte after stimulation with exogenous IFN-γ by flow cytometer. The strength of phosphorylation was described as STAT1 phosphorylation index. Antigen capture assay was performed to measure the relative titer of Immunoglobulin-G fraction of IFN-γ Ab. STAT1 phosphorylation by IFN-γ was significantly inhibited in the leukocytes from patients with disseminated NTM compared to that in healthy subjects, while this inhibition was not observed in patients with pulmonary NTM. All subjects with inhibited STAT1 phosphorylation had high titer of Immunoglobulin-G that reacted with IFN-γ in the antigen capture assay. The measurement of STAT1 phosphorylation index in whole blood leukocytes and antigen capture assay are simple and useful method for detection of anti-IFN-γ neutralizing autoantibodies, and is valuable in the pathophysiological diagnosis of disseminated NTM patients without obvious immunodeficiency.

Analysis of the influenza A (H1N1) 2009 pandemic infection in Japanese asthmatic patients: using a questionnaire-based survey.

BACKGROUND: Influenza infection is known to be an exacerbating factor in the control of asthma, therfore its prevention is critical in managing asthma. The aim of this study was to investigate the influenza A H1N1 2009 pandemic virus (H1N1 pdm09) infection in adult asthmatic patients. METHODS: Data were obtained from a questionnaire-based survey of asthmatic patients conducted from September to October 2010 in Niigata Prefecture. Patient background, H1N1 pdm09 infection, vaccination status, and asthma exacerbation due to influenza infection were analyzed. RESULTS: In total, 2,555 cases were analyzed. The incidence of the infection was 6.7% (95% confidence interval [CI]: 5.7-7.6), and the rate of vaccination was 63.9% (95% CI: 62.1-65.8). The odds ratio (OR) for vaccination against the infection among adult patients and younger patients (≤ the median age) were 0.61 (95% CI: 0.45-0.84) and 0.62 (95% CI: 0.42-0.90), respectively. However, OR among the older patient (> median age) were 1.38 (95%CI: 0.66-2.89). The rate of infection-induced asthma exacerbation was 23.2% (95% CI: 18.6-29.6), and the OR for vaccination against the infection-induced asthma exacerbation was 1.42 (95% CI: 0.69-2.92). CONCLUSIONS: The effectiveness of the vaccination against the H1N1 pdm09 virus was confirmed during the first pandemic season, but it was limited. Further investigation on H1N1 pdm09 virus infection in asthmatics will be required.

Unveiling the role of preceding seasonal influenza in the development of bacteremic pneumococcal pneumonia in older adults before the COVID-19 pandemic in Japan.

OBJECTIVE: We aimed to investigate the impact of preceding seasonal influenza on the clinical characteristics of adult patients with invasive pneumococcal disease (IPD) in Japan. METHODS: Data for 1722 adult patients with IPD were analyzed before (2017-2019) and during the COVID-19 pandemic (2020-2022). RESULTS: The seasonal influenza epidemic disappeared soon after the emergence of the pandemic. Compared with that before the pandemic (66.7%), we observed a lower bacteremic pneumonia proportion in patients with IPD during the pandemic (55.6%). The clinical presentations of IPD cases significantly differed between those with and without preceding influenza. The proportion of bacteremic pneumonia was higher in IPD patients with preceding influenza than in those without in both younger (44.9% vs 84.2%) and older adults (65.5% vs 87.0%) before the pandemic. The case fatality rate was significantly higher in IPD patients with preceding influenza (28.3%) than in those without (15.3%) in older adults before the pandemic (P = 0.020). Male and aging are high risk factors for death in older patients with IPD who had preceding influenza. CONCLUSION: Our study reveals that preceding seasonal influenza plays a role in the development of bacteremic pneumococcal pneumonia, increasing the risk of death in older adults.

Antimicrobial and anti-inflammatory effects of clarithromycin on Mycobacterium avium complex replication in cultured human bronchial epithelial cells.

The Mycobacterium avium complex (MAC) invades cultured human bronchial cells, can replicate intracellularly, and facilitates the release of inflammatory cytokines and chemokines from cells. The purpose of this study was to examine the effects of clarithromycin (CAM) on MAC invasion, replication, and the release of cytokines and chemokines. A human bronchial epithelial cell line (BEAS-2B) monolayer grown on a tissue culture plate was infected with MAC. After 24 h, the cells were washed with Hanks' buffered salt solution, and extracellular bacteria were killed. The monolayer was further cultured for 5 days in medium containing CAM and subjected to a replication assay. The supernatants were assessed using a microchemotaxis assay and enzyme-linked immunosorbent assay (ELISA). mRNA expression was evaluated using a DNA array. The amount of intracellular MAC on day 5 of culture was significantly lower in the presence of CAM at the levels of 1× and 4× MIC. CAM inhibited the release of chemotactic activity and the production of interleukin (IL)-8 and macrophage chemotactic protein (MCP)-1. DNA array analysis of mRNA expression in BEAS-2B cells showed that CAM inhibited the expression of inflammatory cytokines and chemokines, involving IL-6, MCP-1, and IL-8 mRNA. MAC invaded and replicated in BEAS-2B cells and induced the production of chemotactic factors. In contrast, CAM may have bactericidal and bacteriostatic effects leading to the inhibition of inflammatory events.

Dynamic changes in clinical characteristics and serotype distribution of invasive pneumococcal disease among adults in Japan after introduction of the pediatric 13-valent pneumococcal conjugate vaccine in 2013-2019.

Nationwide population-based surveillance for invasive pneumococcal disease (IPD) is being conducted in few Asian countries. We aimed to evaluate the clinical characteristics and serotype distribution among Japanese adult patients with IPD after introduction of the pediatric 13-valent pneumococcal conjugate vaccine (PCV13) in 2013. IPD surveillance was conducted among adults between 2013 and 2019, and 1,995 patients were analyzed by time period (early, 2013-2015; middle, 2016-2017; late, 2018-2019). We found that the period of 2018-2019 was independently associated with a lower risk of fatal outcome, compared with the period of 2013-2015. The proportion of those with serotype PCV13-nonPCV7 decreased significantly in patients aged 15-64 years and in those aged ≥ 65 years within 3 years after the introduction of pediatric PCV13. By contrast, the proportion of those with nonvaccine serotype increased significantly in those aged ≥ 65 years, but not in those aged 15-64 years. No significant change was found in the proportion of 23-valent polysaccharide pneumococcal vaccine (PPSV23)-nonPCV13 in both of adults aged 15-64 years and ≥ 65 years. The proportions of PCV15-, PCV20- and PCV24-covered serotypes were 38%, 56% and 58% in adult patients with IPD aged ≥ 65 years during the late period. Our data on the serotype distribution support an indirect effect from pediatric PCV13 use among adults, and afford a basis for estimates of protection against IPD by vaccination with newly developed PCVs in older adults in Japan.