Yuuki Bamba

Background: Pulmonary nontuberculous mycobacterial (NTM) infections are increasing worldwide; however, data on rare species remain limited. We report a case of pulmonary Mycobacterium kiyosense infection diagnosed following an elevation in the tumor marker carbohydrate antigen 19-9 (CA19-9), which was successfully treated. Case presentation: A 72-year-old woman with a history of subtotal gastrectomy for gastric adenocarcinoma 7 years prior had been followed up for 3 years for chronic bronchitis. Six months before referral, she developed worsening radiographic findings and elevated CA19-9 levels. Upper and lower gastrointestinal endoscopy and positron emission tomography–computed tomography (PET-CT) revealed no evidence of malignancy, except for progressive consolidation in the right lower lobe. Bronchoscopy performed at a previous hospital revealed a slowly growing mycobacterium that could not be identified at the species level, and the patient was referred to our hospital for further evaluation. Sputum cultures obtained at referral and 2 months later were positive for NTM and were initially identified as Mycobacterium gordonae by DNA–DNA hybridization. Whole-genome sequencing (WGS) of these isolates and the earlier strain confirmed Mycobacterium kiyosense (average nucleotide identity, 99.8%). Based on progressive clinical and imaging findings, combination therapy with clarithromycin, ethambutol, and rifampicin was initiated 4 months after referral. Her CA19-9 levels decreased in parallel with radiographic improvement, and sputum culture was negative 8 months after treatment initiation. Treatment was completed after 24 months without recurrence. Conclusions: This is the first reported case of pulmonary M. kiyosense infection successfully treated with a macrolide-based regimen for slowly growing mycobacteria. Clinicians should consider pulmonary NTM infection as a possible cause of elevated CA19-9 levels in the absence of malignancy.

Purpose: Organophosphate (OP) poisoning, a frequent method of suicide in the Asia-Pacific region and rural areas, inhibits cholinesterase (ChE), causing an acute cholinergic crisis. Pneumonia occurs in 20– 50% of these cases, contributing to disease severity and mortality. However, data on the causative pathogens and the risk of drug-resistant bacteria in this patient population are limited. Thus, our study aimed to address these gaps. Patients and Methods: This retrospective cohort study (April 2011–March 2023) investigated patients admitted to the intensive care unit (ICU) or emergency medical center at Niigata University Medical & Dental Hospital with acute OP poisoning. Data on patient demographics, pneumonia diagnosis, sputum culture results, prior antibiotic use, and risk factors for drug-resistant bacteria were collected. We also analyzed the detection rates of methicillin-resistant Staphylococcus aureus and SPICE (Serratia, Pseudomonas, indole-positive Proteus, Citrobacter, and Enterobacter) organisms. Results: Among the 21 patients with OP poisoning, 13 (62%) developed pneumonia and received antibiotic treatment. They had a longer ICU stay, higher Sequential Organ Failure Assessment scores on admission, and lower serum ChE activity (< 100 IU/L). Gram-negative bacilli (GNB) were observed in five sputum cultures from 12 patients with pneumonia, with Pseudomonas aeruginosa isolated from three cases. None of the patients had known risk factors for drug-resistant bacteria. Conclusion: Pneumonia in patients with OP poisoning was predominantly caused by GNB, particularly P. aeruginosa. Thus, despite the absence of known risk factors for drug-resistant bacteria, clinicians should consider the possibility of resistant pathogens when selecting empirical antibiotic therapy for pneumonia in these patients.

Background: Infections can make it difficult to continue peritoneal dialysis (PD). Nontuberculous mycobacteria-associated PD (NTM-PD) infections, while rare, frequently pose a treatment challenge due to their intractable nature and the lack of established therapeutic guidelines. As a result, we aimed to investigate the clinical characteristics of NTM infections in patients undergoing PD. Methods: We retrospectively examined consecutive patients with NTM-PD infections from 2012 to 2022. The cases were identified through microbiological records. The primary outcomes were all-cause mortality and transition to hemodialysis. Secondary outcomes included treatment duration and antimicrobial regimens. Outcomes were compared across different NTM species and between cases with and without infectious disease (ID) consultation. Results: Among 177 patients undergoing PD, we identified 22 NTM infections in 20 patients. The predominant species were M. chelonae (36%), M. fortuitum (36%), and M. abscessus (23%). Twelve patients were transitioned to hemodialysis, with no mortality. All M. abscessus infections ( n =  5) required transition to hemodialysis, compared to 46% in other species. ID consultation ( n =  15) was linked to more frequent antimicrobial susceptibility testing (60% vs. 0%, p <  .05), longer treatment duration (5.7 vs. 1.2 months, p <  .05), and increased use of combination therapies (100% vs. 43%, p <  .05). However, ID consultation did not affect the frequency of transition to hemodialysis. Conclusion: Early identification of NTM species and timely ID consultation can help optimize management strategies for these challenging infections.

Early intervention is imperative in cases of Japanese spotted fever (JSF) due to its potentially fatal trajectory if diagnosed belatedly. JSF should be contemplated in the differential diagnosis when generalized purpura, accompanied by a pronounced inflammatory response, is noted, even in the absence of a puncture wound.

Aspergillus-specific antibodies are diagnostic indicators of allergic bronchopulmonary aspergillosis (ABPA) and chronic pulmonary aspergillosis (CPA). Tests for detecting Aspergillus-specific antibodies were not used clinically in Japan, and the production of the Aspergillus precipitin test was discontinued. Thus, alternative tests for diagnosing aspergillosis are urgently needed. We retrospectively evaluated 64 patients with suspected ABPA and CPA who underwent precipitin antibody testing. Serum Aspergillus IgG levels were measured and compared using the Bordier Aspergillus fumigatus ELISA and the Platelia Aspergillus IgG (Bio-Rad) kits. Of the participants, 18 were diagnosed with CPA, and 8 were diagnosed with ABPA. Both the Bordier and Bio-Rad kits showed high sensitivity and specificity for CPA and ABPA. The area under the receiver operating characteristic curves for the Bordier and Bio-Rad kits were 0.97 and 0.95, respectively, for CPA, and 0.89 and 0.91, respectively, for ABPA. In contrast to the Bordier kit, the Bio-Rad kit showed relatively low anti-Aspergillus IgG levels and lower sensitivity to non-fumigatus Aspergillus infections. The Aspergillus-specific IgG ELISA tests showed sufficient diagnostic accuracy. Therefore, these assays are recommended as alternatives to the precipitin kit for diagnosing aspergillosis in clinical settings in Japan.

The close relationship between infectious diseases and iron metabolism is well known, but a more detailed understanding based on current knowledge may provide new insights into the diagnosis and treatment of infectious diseases, considering the growing threat of antibiotic-resistant bacteria. This study investigated adult patients with bloodstream infections, temporal changes, and relationships between blood levels of iron and related markers, including hepcidin and lipocalin-2 (LCN2). We included 144 samples from 48 patients (mean age 72 years, 50% male), with 30 diagnosed with sepsis. During the acute phase of infection, blood levels of hepcidin and LCN2 increased rapidly, whereas iron levels decreased, with values in 95.8% of cases below the normal range (40–188 μg/dL). Later, hepcidin and LCN2 decreased significantly during the recovery phase, and the decreased iron concentrations were restored. In the case of persistent inflammation, iron remained decreased. Acute LCN2 levels were significantly higher in patients with sepsis (p < 0.01). Hypoferremia induced by increased hepcidin would reduce iron in the environment of extracellular pathogens, and the increased LCN2 would inhibit siderophores, resulting in the prevention of the pathogen’s iron acquisition in each manner during the acute phase of bloodstream infection.