Publications by authors named "Hiroaki Ikegami"

Background: Non-vaccine serotype (NVT) pneumococcal pneumonia in Japan has increased with the spread of pneumococcal vaccinations. However, there is no data regarding the clinical background and antimicrobial susceptibility of NVT isolates compared with those of vaccine serotype (VT) isolates in adult pneumococcal pneumonia.

Methods: The serotypes and antimicrobial susceptibilities of pneumococcal isolates obtained from patients with pneumonia at the University of Occupational and Environmental Health, Japan, from January 2011 to December 2020 were retrospectively evaluated along with the patients' clinical information.

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"The infectious organism lurking in human airways (IOLA)" is a candidate pathogenic bacterium detected in bronchoalveolar lavage fluid specimens derived from adult patients with chronic lower respiratory tract infections. Genomic analyses of IOLA have revealed that it possesses the smallest and most AT-rich genome among human-derived bacteria. However, its biological properties remain unclear because no culture method has been established for IOLA.

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  • Paragonimiasis is a parasitic disease in Japan, commonly contracted from undercooked crustaceans or wild boar meat, with significant data gaps in its nationwide epidemiology.
  • A study analyzed hospitalized patients diagnosed with pulmonary paragonimiasis from April 2012 to March 2020, involving 73 patients in total, with an average age of 49.7 years and average hospital stay of 12.5 days.
  • The majority of cases were found in the Kyushu region, particularly Fukuoka Prefecture, highlighting the need for medical professionals to remain vigilant about this disease in affected areas.
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A 73-year-old Japanese woman with productive cough and dyspnoea on exertion was admitted, and she showed neutropenia and pulmonary reticular opacities and axial and mediastinal lymphadenopathies on chest computed tomography. The clinical findings and surgical lung and lymph node biopsies were diagnostic for idiopathic multicentric Castleman's disease (iMCD) complicated by secondary autoimmune neutropenia (AIN). iMCD is often complicated with hematologic disorders, however, iMCD complicated with AIN has not been reported; therefore, if iMCD is accompanied by neutropenia, the anti-neutrophil antibodies should be measured.

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  • A 77-year-old Japanese woman was diagnosed with sarcoidosis after presenting with mediastinal lymphadenopathy and uveitis.
  • * Researchers used Sanger sequencing to analyze the bacterial flora from her biopsied mediastinal lymph nodes and found Streptococcus gordonii and Cutibacterium acnes.
  • * This case report is significant as it is the first to document these specific bacteria in the mediastinal lymph nodes of a sarcoidosis patient using the Sanger method.
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  • A nationwide surveillance study in Japan assessed the antimicrobial susceptibility of bacterial pathogens related to respiratory tract infections, collecting data from June 2019 to December 2020.
  • The study analyzed 932 bacterial strains from 32 medical facilities, finding notable resistance rates, such as 35.3% for methicillin-resistant Staphylococcus aureus and 16.2% for β-lactamase-producing resistant Haemophilus influenzae.
  • Results from this surveillance aim to inform treatment strategies for respiratory infections in Japan and promote the responsible use of antimicrobial drugs.
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  • Co-infection with nontuberculous mycobacteria (NTM) and other bacteria can lead to more hospitalizations and lower quality of life, but the impact of this co-infection is not fully understood.
  • The study analyzed alveolar macrophage populations and their ability to phagocytose bacteria in patients with NTM lung disease, using samples from 30 patients, including those infected with Mycobacterium avium complex (MAC).
  • Results showed that MAC-infected patients had more non-polarized macrophages with impaired ability to phagocytose Staphylococcus aureus, while M. intracellulare-infected macrophages exhibited reduced ability to kill bacteria in vitro, indicating a problematic cycle of
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  • The study evaluates bacterial flora in bronchoalveolar lavage fluid (BALF) from pneumonia patients using advanced 16S rRNA gene analysis, aiming to better understand the bacteria present in pneumonia lesions compared to traditional culture methods.
  • Researchers collected and analyzed samples from 294 pneumonia patients at a Japanese hospital over ten years, comparing different pneumonia types (community-acquired, healthcare-associated, and hospital-acquired) and gathering relevant clinical information.
  • Findings revealed that community-acquired pneumonia (CAP) patients displayed higher levels of obligate anaerobes, while specific bacteria like Corynebacterium and Streptococcus pneumoniae were linked to certain patient conditions, emphasizing the need for refined diagnostic approaches.
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The study objective was to evaluate chest radiographic features that distinguish Mycoplasma pneumoniae pneumonia (MPP) from other bacterial pneumonias diagnosed based on the bacterial floral analysis with 16S rRNA gene sequencing, using bronchoalveolar lavage fluid samples directly obtained from pneumonia lesions. Patients were grouped according to the dominant bacterial phenotype; among 120 enrolled patients with CAP, chest CT findings were evaluated in 55 patients diagnosed with a mono-bacterial infection (one bacterial phylotype occupies more than 80% of all phylotypes in a sample) by three authorized respiratory physicians. Among this relatively small sample size of 55 patients with CAP, 10 had MPP, and 45 had other bacterial pneumonia and were categorized into four groups according to their predominant bacterial phylotypes.

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A 15-year-old male presented with headache, high fever and respiratory distress. Chest computed tomography showed bilateral pneumonia, and antimicrobial therapy was initiated. However, his respiratory condition deteriorated, and he developed respiratory failure requiring intubation.

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  • * Out of the evaluated patients, the most common causes of pleurisy were found to be neoplastic diseases (55.9%), particularly malignant mesothelioma and lung cancer, followed by infectious diseases (24.0%), with tuberculosis being the most prevalent among them.
  • * The findings suggest that surgical pleural biopsy is crucial for accurately diagnosing pleurisy, particularly in cases where needle biopsy results are inconclusive, guiding physicians towards better management of the condition.
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  • Next-generation sequencing (NGS) is being used to analyze bacterial flora in respiratory infections, but there's no standard protocol and the best clustering threshold for bacterial species is unclear.
  • This study compared NGS results with the more accurate Sanger sequencing method to find the optimal threshold for clustering 16S ribosomal RNA gene sequences into operational taxonomic units (OTUs).
  • Results showed that a 100% clustering threshold with NGS had higher concordance with Sanger results, especially for Streptococcus mitis group specimens, indicating that full sequence identity is essential for reliable microbiota analysis in these infections.
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  • * Out of the patients, 12 were diagnosed with SAG-mediated empyema; a higher detection rate of obligate anaerobes was observed using a clone library method compared to standard culture analysis.
  • * Results showed no significant clinical differences in SAG-mediated empyema cases with or without anaerobes, but radiological features varied, suggesting that traditional culture methods might underestimate the co-infection rates and that more research is needed.
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  • Recent advancements in microbiology have improved our understanding of unculturable microbes, but new human pathogenic bacteria have been seldom discovered.
  • The newly identified bacterium, named IOLA, has a complete genome size of 303,838 bp and a very low GC content, making it the smallest and most AT-rich human-associated bacterial genome known so far.
  • IOLA is linked to respiratory infections and can persist in the respiratory tract for at least 15 months, suggesting it's a potential new pathogen associated with human respiratory diseases.
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  • * After 6 days, he was intubated and given high doses of methylprednisolone, which briefly improved his respiratory condition but did not last long.
  • * He was later diagnosed with invasive pulmonary aspergillosis related to COVID-19 after Aspergillus fumigatus was found in his tracheal aspirate, and despite treatment with amphotericin B, he passed away 28 days after being admitted.
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Pseudoaneurysm should be considered in the differential diagnosis when the computed tomography (CT) findings show a mediastinal mass in patients with a history of cardiovascular surgery even if such surgery occurred over two decades previously.

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  • Mycobacterial culture is the standard method for diagnosing nontuberculous Mycobacterium (NTM) infections, but it struggles to identify cases with multiple different NTMs present.
  • A study analyzed BAL fluid samples from 120 patients and found that using clone library methods allowed for detection of both single and multiple NTM phylotypes, revealing that 11 patients initially deemed NTM negative by culture were NTM positive via clone analysis.
  • The research suggests that patients with multiple NTM phylotypes have worse chest CT outcomes and highlights the need for ongoing monitoring of patients with initial negative culture results to catch any later NTM infections more quickly.
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A 37-year-old Japanese man presented with a bulla with niveau-like opacity in the right upper lung on chest radiography. Air-fluid level gradually increased despite broad-spectrum antibiotic therapy. Right upper lobectomy was performed, and epithelioid granuloma with mycobacteria was histopathologically observed.

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A 67-year-old man with a pulmonary cavity was admitted to our hospital. Mycobacterial culture of the bronchoalveolar lavage fluid sample obtained from the right upper pulmonary lesion tested positive for mycobacterium, and sequencing of the 16S rRNA genes, hsp65, and rpoB revealed that the cultured mycobacterium was Mycobacterium parascrofulaceum. Treatment with antimycobacterial agents was ineffective, and repeated culturing of bronchoscopic specimens revealed that the specimens were positive for Aspergillus fumigatus.

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Background: Oral cavity is a reservoir of various respiratory pathogens, and poor oral hygiene is associated with an increase in anaerobic bacteria in oral cavity. In addition, it positively relates higher risk of developing pneumonia and increased pneumonia-related mortality. However, the association between poor oral hygiene and increase in obligate anaerobes in the lungs of pneumonia patients is unclear.

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In 2014, vaccinations with 23-valent pneumococcal polysaccharide vaccine (PPSV23) and 13-valent pneumococcal conjugate vaccine (PCV13) were implemented in Japan for all adults aged ≥65 years. We previously clarified reductions in the proportions of PCV7-, PCV13-, and PPSV23-covered serotypes in patients with pneumococcal pneumonia after the initiation of PCV7 and PCV13 vaccinations for Japanese children; however, information about the annual changes in the proportion of Streptococcus pneumoniae serotypes in patients with pneumococcal pneumonia after the initiation of routine PPSV23 vaccinations remains unclear. We retrospectively studied 229 adults with pneumococcal pneumonia which S.

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Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) has been widely used in Japan. The guidelines of the American College of Chest Physicians has recommended that EBUS-TBNA should be performed by well-trained operators who can perform highly accurate procedures, but the indicators of the degree of experience and training are unclear. In our department, physicians who do not have enough experience perform EBUS-TBNA under the supervision of bronchoscopic instructors who have EBUS-TBNA techniques (Board Certified Member of the Japan Society for Respiratory Endoscopy) after guidance and training in EBUS-TBNA using a simulator as an operator and helper.

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An eighty-nine-year-old Japanese male was admitted to our hospital due to dry cough and dyspnea. Respiratory symptoms appeared soon after an administration of an oriental medicine, Kamikihito for tinnitus. Upon admission, chest computed tomography showed patchy consolidations and ground-glass opacities in the right upper lobe of the lungs, and ground-glass opacities in the bilateral lower lobes.

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