港 雄介

Mycobacterium abscessus exhibits high intrinsic drug resistance, requiring combination therapy. We developed a silkworm (Bombyx mori) infection model as a whole-organism, in vivo-based platform for quantitative, outcome-based evaluations of antimicrobial combinations. The system, examined using clarithromycin-amikacin and imipenem-cefoxitin combinations, showed interaction profiles that were qualitatively consistent with those observed in vitro. This rapid, reproducible, and ethical assay enables reliable phenotypic assessments of synergistic or antagonistic effects and may facilitate the evaluation and prioritization of antimicrobial combination regimens in preclinical studies.

Evidence regarding the diagnostic value of quantitative interferon-gamma release assay (IGRA) results in elderly populations is limited, and large-scale data for QuantiFERON-TB Gold Plus (QFT-Plus) are scarce. We evaluated QFT-Plus and T-SPOT.TB (T-SPOT) for distinguishing active tuberculosis (ATB) from latent infection (LTBI) in elderly individuals in Japan, a super-aged country. We conducted a retrospective, cross-sectional diagnostic accuracy study of patients ≥65 years who underwent IGRA testing between 2015 and 2024 at two hospitals: a tuberculosis referral center (QFT-Plus and T-SPOT) and a tertiary hospital (T-SPOT only). ATB was defined as microbiologically confirmed TB. Quantitative IGRA values were compared between ATB and LTBI in all patients and in IGRA-positive subsets. Receiver operating characteristic (ROC) curves assessed discriminatory performance. Among 10,745 elderly patients (ATB: n = 310; LTBI: n = 1,158), values showed substantial overlap. For T-SPOT, the area under the curves (AUCs) improved at Tosei General Hospital (TGH) (ESAT-6: 0.679, CFP-10: 0.670) in IGRA-positive cases. In contrast, all-patient AUCs at Fujita Health University Hospital (FHUH) were low (ESAT-6: 0.367, CFP-10: 0.362), demonstrating an inverse association, though they improved (ESAT-6: 0.607 and CFP-10: 0.554) in IGRA-positive cases. For QFT-Plus, all-patient AUCs were low (TB1 antigen: 0.462, TB2 antigen: 0.470), but improved in the IGRA-positive cohort (TB1 antigen: 0.630, TB2 antigen: 0.645). The optimal quantitative cutoffs in IGRA-positive cases provided modest diagnostic accuracy. In elderly individuals, quantitative IGRA values alone have limited ability to distinguish ATB from LTBI, but QFT-Plus and T-SPOT show modest improvement in IGRA-positive cases. Although not suitable as a stand-alone diagnostic, quantitative IGRA may assist risk stratification and decision-making in selected scenarios.IMPORTANCETuberculosis remains a major health concern in aging societies, such as Japan, where most patients are elderly adults with impaired immune function. Interferon-gamma release assays (IGRA) are widely used for detecting infection, but the role of their quantitative values in differentiating active tuberculosis from latent tuberculosis infection has been uncertain. Our study is the first to evaluate the quantitative performance of the latest QuantiFERON-TB Gold Plus and T-SPOT.TB specifically in elderly patients, across both a tuberculosis referral hospital and a university hospital. Although absolute separation between active and latent disease was not achieved, we found that, in test-positive individuals, active cases tended to yield higher values, particularly with T-SPOT.TB. This indicates that quantitative information, when interpreted within the clinical context, can assist physicians in assessing risk and guiding further diagnostic steps, offering practical value for improving decision-making in the care of vulnerable elderly patients.

OBJECTIVE: Mycobacterium lentiflavum is a rare, non-tuberculous mycobacterium (NTM) which is implicated in some cases of active, pulmonary non-tuberculous mycobacterial disease. The outbreak of NTM in nosocomial settings occasionally occurs and outbreak investigation with implementation of concurrent countermeasure is essential. DESIGN: Outbreak investigation. SETTING: A tertiary care medical center. PATIENTS AND PARTICIPANTS: Hospitalized patients during the outbreak period. RESULTS: In April 2024, a cluster of patients with Mycobacterium lentiflavum-positive sputum cultures, presumed to be due to nosocomial transmission, was identified at the study center. A retrospective review of cases dating back to February 2023 revealed 27 patients with M. lentiflavum infection whose isolates had initially not been speciated. According to the American Thoracic Society (ATS) criteria for diagnosing pulmonary non-tuberculous mycobacterial (NTM) disease, two of these patients met the criteria for active disease. Multi-locus sequence typing of 12 isolates demonstrated 100% clonality, indicating a common source. A concurrent outbreak investigation identified contaminated faucet aerators in hospital wards as the likely source of transmission. All faucet aerators and caps were manually cleaned and disinfected using liquid sodium hypochlorite, after which no further cases were detected. CONCLUSION: The present study described a nosocomial cluster of M. lentiflavum colonization and infections at a tertiary care center, with contaminated faucet aerators identified as the likely source. Prompt identification of such NTM clusters in healthcare settings is essential to initiate timely treatment and prevent further transmission.

Mycobacterium intracellulare is a major etiological agent of the recently expanding Mycobacterium avium-intracellulare complex pulmonary disease (MAC-PD). Therapeutic regimens that include a combination of macrolides and antituberculous drugs have been implemented with limited success. To identify novel targets for drug development that accommodate the genomic diversity of M. avium-intracellulare, we subjected eight clinical MAC-PD isolates and the type strain ATCC13950 to genome-wide profiling to comprehensively identify universally essential functions by transposon sequencing (TnSeq). Among these strains, we identified 131 shared essential or growth-defect-associated genes by TnSeq. Unlike the type strain, the clinical strains showed increased requirements for genes involved in gluconeogenesis and the type VII secretion system under standard growth conditions, the same genes required for hypoxic pellicle-type biofilm formation in ATCC13950. Consistent with the central role of hypoxia in the evolution of M. intracellulare, the clinical MAC-PD strains showed more rapid adaptation to hypoxic growth than the type strain. Importantly, the increased requirements of hypoxic fitness genes were confirmed in a mouse lung infection model. These findings confirm the concordant genetic requirements under hypoxic conditions in vitro and hypoxia-related conditions in vivo and highlight the importance of using clinical strains and host-relevant growth conditions to identify high-value targets for drug development.

BACKGROUND: Flomoxef and cefmetazole have been reported to be effective against broad-spectrum β-lactamase-producing bacteria and have gained attention as a potential alternative to carbapenems. This study aimed to compare the efficacy of these two drugs in treating urinary tract infection (UTI) by integrating in vitro data and two real-world databases. METHODS: The susceptibility rates of third-generation cephalosporin-resistant Escherichia coli and Klebsiella pneumoniae to flomoxef and cefmetazole were compared using comprehensive national antimicrobial resistance surveillance data. Combined antimicrobial activities against an extended-spectrum beta-lactamase (ESBL)-producing multidrug-resistant bacterial strain were tested by diagonal measurement of n-way drug interactions. The effectiveness of the two drugs in treating UTIs was compared using hospital stay duration data obtained from the Japan Medical Data Center (JMDC) Claims Database. RESULTS: Third-generation cephalosporin-resistant E. coli and K. pneumoniae, including ESBL-producing strains, were similarly susceptible to flomoxef and cefmetazole. In vitro assessment against an ESBL-producing multidrug-resistant strain revealed similar antimicrobial interaction patterns. JMDC Claims data analysis showed that the median hospital stay was 11 (95% confidence interval [CI]: 11-11) and 4 (95% CI: 3-5) days in the cefmetazole and flomoxef groups, respectively (log-rank test, P < 0.001). Moreover, the flomoxef group demonstrated a significantly lower frequency of adverse events such as C. difficile infection and renal failure. CONCLUSIONS: The effectiveness of flomoxef is comparable to that of cefmetazole in treating UTIs without major complications. Thus, flomoxef is a viable treatment option for UTIs in locales with a high prevalence of ESBL-producing strains.