Relapsing bronchopneumonia due to community-associated methicillin-resistant Staphylococcus aureus: a case report.

BACKGROUND: The emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has increased the incidence of community-onset MRSA infection. Respiratory tract infections caused by MRSA has been noted for their severity; however, repeated relapses that require extended antibiotic therapy are rare. CASE PRESENTATION: We report a case of relapsing bronchopneumonia caused by CA-MRSA in a 56-year-old man. The patient responded to antibiotics, but repeatedly relapsed after stopping treatment. MRSA was consistently isolated from airway specimens during each relapse. Extended oral antibiotic treatment with trimethoprim/sulfamethoxazole (TMP/SMX) for 6 months achieved infection control. Whole-genome sequencing of the isolated strain revealed that the causative agent was sequence type (ST)1/staphylococcal cassette chromosome mec (SCCmec) type IVa, a clone that is rapidly increasing in Japan. DISCUSSION AND CONCLUSIONS: This patient had an unusual course of MRSA bronchopneumonia with repeated relapses. Although the choice of antibiotics for long-term use in MRSA respiratory tract infections has not been well established, TMP/SMX was effective and well tolerated for long-term therapy in this case. The clinical course of infections related to the rapid emerging clone, ST1/SCCmec type IVa warrants further attention.

A Case of Solitary Pure Ground-glass Opacity Suspected of Being the Initial Presentation of Nonfibrotic Hypersensitivity Pneumonitis.

We herein report a rare case of hypersensitivity pneumonitis (HP) that was initially demonstrated as solitary pure ground-glass opacity (GGO) on chest computed tomography (CT). A 51-year-old woman with a history of breast cancer underwent follow-up CT, which revealed solitary pure GGO. The patient developed exertional dyspnea after two years, and CT revealed diffuse centrilobular nodules in addition to GGO, which had increased in size. An antigen avoidance test was performed to diagnose HP, leading to the resolution of CT abnormalities, including the GGO. Our findings suggested that nonfibrotic HP can present as solitary pure GGO.

Assessment of clinical relevance of antigen improves diagnostic accuracy of hypersensitivity pneumonitis.

BACKGROUND: Exposure assessment is integral to the diagnosis of hypersensitivity pneumonitis (HP). Although the clinical relevance of exposed antigens is essential for the assessment, many of the previous guidelines or reports have only evaluated simple exposure histories or immunological tests. To overcome this problem, the Exposure Assessment Form (EAF) was developed as an assessment tool for classifying the exposure grade from G0 to G4. The EAF was modified from the description in the Japanese clinical practice guide 2022 for HP published by the Japanese Respiratory Society. METHODS: One hundred and seventy-two consecutive patients with interstitial lung disease who underwent multidisciplinary discussion (MDD) at our hospital were retrospectively examined. We assessed whether the use of the EAF improved the diagnostic performance of the international guideline of HP. We also evaluated whether the exposure grade affected the prognosis of HP. RESULTS: Even when a HP diagnosis was made with a confidence of 70% or higher according to the international guideline, less than half of these cases resulted in a final diagnosis of HP when the exposure grades were lower than G3. When the result of the EAF was integrated into the exposure definition of the international guideline, the specificity of the diagnostic performance improved, while sensitivity was maintained. Furthermore, HP patients with an exposure grade of G3 or higher showed a tendency to take a longer time to initiate medication. CONCLUSIONS: This is the first study to evaluate the clinical relevance of possible antigens using the EAF. Assessing the exposure grade prevents overdiagnosis and improves the diagnostic performance of the international guideline.

Pulmonary Artery Aneurysm in a Patient with Nontuberculous Mycobacteria Infection.

Nontuberculous mycobacterial (NTM) infection sometimes leads to the development of pulmonary artery aneurysm (PAA), a rare but life-threatening complication. We herein report a 64-year-old woman with a history of NTM infection who presented with severe hemoptysis. Computed tomography revealed a ruptured PAA, which was treated successfully with pulmonary artery embolization. Subsequent right total pneumonectomy was performed to control infection. This case emphasizes the need to consider PAA in patients with NTM infection who present with hemoptysis. Early detection and appropriate management are critical for preventing this fatal complication.

COVID-19 Pneumonia Followed by Anti-signal Recognition Particle Antibody-positive Fibrosing Interstitial Lung Disease.

Coronavirus disease 2019 (COVID-19) pneumonia is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is frequently accompanied by various sequelae. Interstitial lung diseases (ILDs) are observed in COVID-19 pneumonia patients after recovery, probably due to persistent inflammation in the lungs. We herein report a case of ILD with anti-signal recognition particle antibodies following severe COVID-19 pneumonia. The patient was diagnosed with ILD three months after COVID-19 pneumonia. Although the exact mechanism is unknown, the autoantibody-induced immune response might have been the pulmonary fibrosis trigger in this patient.

Association of SARS-CoV-2 RNA Copy Number with the COVID-19 Mortality Rate and Its Effect on the Predictive Performance of Mortality in Severe Cases.

Factors associated with mortality are important in the treatment of coronavirus disease 2019 (COVID-19). Polymerase chain reaction (PCR) is the gold standard for diagnosing COVID-19, which reflects the viral load in the upper respiratory tract. In total, 523 patients were enrolled in this study; of them, 441 and 75 patients underwent PCR testing of nasopharyngeal swabs and sputum samples, respectively, within 20 days from onset of COVID-19. We investigated the association between RNA copy number and the COVID-19 severity and mortality rate and its effect on the predictive performance for severity and mortality. RNA copy numbers in nasopharyngeal swabs were higher in the non-survivor group than in the survivor group. Multivariate logistic regression analysis identified that the high RNA copy number (≥9 log10 /swab) in nasopharyngeal swabs was a factor associated with mortality (odds ratio, 4.50; 95% confidence interval, 1.510-13.100; P = 0.008). Furthermore, adding RNA copy number (≥9 log10 /swab) in severe cases, adjusted by duration from onset to PCR, improved mortality predictive performance based on known factors. The RNA copy number is a factor associated with the mortality of patients with COVID-19 and can improve the predictive performance of mortality in severe cases.

IL-17A-Secreting Memory γδ T Cells Play a Pivotal Role in Sensitization and Development of Hypersensitivity Pneumonitis.

Hypersensitivity pneumonitis (HP) typically presents with interstitial inflammation and granulomas induced by an aberrant immune response to inhaled Ags in sensitized individuals. Although IL-17A is involved in the development of HP, the cellular sources of IL-17A and the mechanisms by which IL-17A contributes to granuloma formation remain unclear. Recent studies report that γδ T cells produce IL-17A and exhibit memory properties in various diseases. Therefore, we focused on IL-17A-secreting memory γδ T cells in the sensitization phase and aimed to elucidate the mechanisms by which IL-17A contributes to granuloma formation in HP. We induced a mouse model of HP using pigeon dropping extract (PDE) in wild-type and IL-17A knockout (IL-17A-/-) mice. IL-17A-/- mice exhibited reduced granulomatous areas, attenuated aggregation of CD11b+ alveolar macrophages, and reduced levels of CCL2, CCL4, and CCL5 in the bronchoalveolar lavage fluid. Among IL-17A+ cells, more γδ T cells than CD4+ cells were detected after intranasal PDE administration. Interestingly, the expansion of IL-17A-secreting Vγ4+ or Vγ1-Vγ4- cells of convalescent mice was enhanced in response to the sensitizing Ag. Additionally, coculture of macrophages with PDE and Vγ4+ cells purified from PDE-exposed convalescent mice produced significantly more IL-17A than coculture with Vγ4+ cells from naive mice. Our findings demonstrate that in the sensitization phase of HP, IL-17A-secreting memory γδ T cells play a pivotal role. Furthermore, we characterized the IL-17A/CCL2, CCL4, CCL5/CD11b+ alveolar macrophage axis, which underlies granuloma formation in HP. These findings may lead to new clinical examinations or therapeutic targets for HP.

Serum CXCL9 and CCL17 as biomarkers of declining pulmonary function in chronic bird-related hypersensitivity pneumonitis.

The clinical course of chronic hypersensitivity pneumonitis (HP) with fibrosis is similar to that of idiopathic pulmonary fibrosis (IPF). Current research is expected to identify biomarkers effective in predicting the deterioration of lung function in a clinical setting. Our group analyzed the relationships between the following parameters in chronic bird-related HP: patient characteristics, serum markers, lung function, HRCT findings, BALF profiles, and the worsening of lung function. We also analyzed serum levels of CXCL9, CCL17, and Krebs von den Lungen 6 (KL-6) as serum markers. Patients showing declines in vital capacity (VC) of over 5% at 6 months after first admission were categorized as the "decline group"; the others were categorized as the "stable group." The serum level of CCL17 and the percentage of BALF macrophages were significantly higher in the decline group compared to the stable group. Serum levels of CXCL9 and CCL17 were significant variables in a multivariate logistic regression analysis of factors associated with VC decline. Patients with a chemokine profile combining lower serum CXCL9 and higher serum CCL17 exhibited significantly larger VC decline in a cluster analysis. Higher serum CCL17 and lower serum CXCL9 were important predictors of worsening lung function in patients with chronic bird-related HP.

[Independent Occurrence of a Mediastinal Bronchogenic Cyst and an Intralobar Pulmonary Sequestration].

Here we describe a case of an 18-year-old boy who exhibited abnormal pulmonary parenchyma supplied by an aberrant artery from the descending aorta in the right lower lobe of the lung and a cystic tumor measuring 34×26×54 mm in the right upper mediastinum. Video-assisted thoracic surgery for resection of the 2 lesions showed that they were independent of each other. Final diagnosis of an intralobar pulmonary sequestration in the right lower lobe and a bronchogenic cyst in the upper mediastinum was made. In some reports, 2 lesions were described to be in close proximity to and connected with each other, but the present case is unique in that the 2 lesions were completely independent of each other.