Beyond Symptoms: Radiologic identification of asymptomatic Mycobacterium avium complex pulmonary infections.

BACKGROUND: Although international nontuberculous mycobacterial pulmonary disease (NTM-PD) guidelines highlight symptom presence at diagnosis, the clinical characteristics of asymptomatic Mycobacterium avium complex pulmonary infection (MAC-PI) patients remain understudied. We clarified the clinical characteristics and course of asymptomatic MAC-PI patients. METHODS: We retrospectively analyzed 200 consecutive patients with MAC-PIs and adequate available data who newly met the microbiological and radiological criteria for NTM-PD at Fukujuji Hospital from January 2018 to June 2020. We compared the clinical characteristics and course of asymptomatic patients with symptomatic patients and evaluated factors influencing treatment initiation through multivariate analysis. RESULTS: 111 patients were symptomatic and 89 were asymptomatic at diagnosis. While the proportion was significantly lower than that in the symptomatic group (28.8 %), 15.7 % of asymptomatic group patients had cavitary lesions (P = 0.042). In the asymptomatic group, treatments were initiated in 38 (42.7 %) patients, and cavitary lesions, a positive acid-fast bacilli smear, and younger age were independent risk factors for treatment initiation. Among 22 (57.9 %) patients who experienced disease progression necessitating treatment during follow-up, 13 (34.2 %) displayed radiological progression without any worsening of symptoms. Agents used for treatment were consistent across the groups, with no significant differences in culture conversion, microbiological recurrence rates, or spontaneous culture conversion rates. CONCLUSION: Routine health checkups and radiological examinations can detect clinically important MAC-PIs even in the absence of symptoms. Considering that the clinical course of asymptomatic MAC-PI patients is largely similar to that of symptomatic patients, timely and appropriate management and intervention are essential for all MAC-PI patients.

Practical guide for the diagnosis and management of primary ciliary dyskinesia.

OBJECTIVE: Primary ciliary dyskinesia (PCD) is a relatively rare genetic disorder that affects approximately 1 in 20,000 people. Approximately 50 genes are currently known to cause PCD. In light of differences in causative genes and the medical system in Japan compared with other countries, a practical guide was needed for the diagnosis and management of Japanese PCD patients. METHODS: An ad hoc academic committee was organized under the Japanese Rhinologic Society to produce a practical guide, with participation by committee members from several academic societies in Japan. The practical guide including diagnostic criteria for PCD was approved by the Japanese Rhinologic Society, Japanese Society of Otolaryngology-Head and Neck Surgery, Japanese Respiratory Society, and Japanese Society of Pediatric Pulmonology. RESULTS: The diagnostic criteria for PCD consist of six clinical features, six laboratory findings, differential diagnosis, and genetic testing. The diagnosis of PCD is categorized as definite, probable, or possible PCD based on a combination of the four items above. Diagnosis of definite PCD requires exclusion of cystic fibrosis and primary immunodeficiency, at least one of the six clinical features, and a positive result for at least one of the following: (1) Class 1 defect on electron microscopy of cilia, (2) pathogenic or likely pathogenic variants in a PCD-related gene, or (3) impairment of ciliary motility that can be repaired by correcting the causative gene variants in iPS cells established from the patient's peripheral blood cells. CONCLUSION: This practical guide provides clinicians with useful information for the diagnosis and management of PCD in Japan.

Primary Ciliary Dyskinesia Caused by Homozygous DNAAF1 Mutations Resulting from a Consanguineous Marriage: A Case Report from Japan.

We present the case of a 58-year-old female patient with primary ciliary dyskinesia (PCD). She was born to parents with a consanguineous marriage. Chest computed tomography conducted at age 41 years indicated no situs inversus, and findings of bronchiectasis were limited to the middle and lingular lobes. Despite long-term macrolide therapy, bronchiectasis exacerbations frequently occurred. PCD was suspected because of the low nasal nitric oxide level (20.7 nL/min). Electron microscopy revealed outer and inner dynein arm defects, and a genetic analysis identified a homozygous single-nucleotide deletion in the DNAAF1 gene. Based on these results, the patient was diagnosed with PCD due to a biallelic DNAAF1 mutation.

Pseudo-Meigs' Syndrome With Eosinophilic Pleural Effusion.

We present a rare case of a 45-year-old woman with pseudo-Meigs' syndrome and eosinophilic pleural effusion (EPE). She experienced cough, sputum, and dyspnea with a large right pleural effusion. Laboratory tests showed eosinophilia in the blood and pleural fluid. An ovarian tumor and ascites were also detected. After left salpingo-oophorectomy, the tumor was diagnosed as a mature cystic teratoma of the left ovary. The right-sided pleural effusion gradually resolved. Pseudo-Meigs' syndrome is characterized by benign ovarian tumor, ascites, and pleural effusion. Typically, it is associated with exudate pleural effusion characterized by a predominance of mononuclear cells. The occurrence of eosinophilic pleural effusion in our patient may be exceptionally rare.

Amikacin liposome inhalation suspension for Mycobacterium avium complex pulmonary disease: A subgroup analysis of Japanese patients in the randomized, phase 3, CONVERT study.

BACKGROUND: CONVERT, a randomized, active-controlled, global, Phase 3 trial demonstrated that patients with treatment-refractory Mycobacterium avium complex (MAC) pulmonary disease were more likely to achieve culture conversion with amikacin liposome inhalation suspension (ALIS) plus guideline-based therapy (GBT) versus those continuing on GBT alone. This subgroup analysis reports the efficacy and safety of ALIS in Japanese patients enrolled in CONVERT. METHODS: Japanese patients aged ≥20 years with treatment-refractory MAC pulmonary disease from Japanese sites were included. Patients were randomized to receive once-daily 590 mg ALIS + GBT or GBT alone; patients converting by Month 6 remained in the study to complete 12-month treatment followed by a 12-month off-treatment period. Nonconverters exited the study at Month 8. The primary endpoint was the proportion of patients achieving culture conversion by Month 6. RESULTS: Of the 59 Japanese patients screened, 48 were randomized to receive ALIS + GBT (n = 34) or GBT alone (n = 14), and 41/48 (85.4 %) were women. The mean (standard deviation) age of patients was 64.5 (8.6) years, and 83.3 % of patients had bronchiectasis at baseline. By Month 6, sputum culture conversion was cumulatively achieved in 9/34 (26.5 %) patients receiving ALIS + GBT versus none receiving GBT alone. Treatment-emergent adverse events were reported in 94.1 % and 100.0 % of patients receiving ALIS + GBT and GBT alone, respectively. No deaths were reported. CONCLUSIONS: The efficacy observed in the Japanese subpopulation was largely consistent with that in the overall CONVERT study population, with more patients achieving culture conversion with ALIS + GBT versus GBT alone. Safety profiles were similar between the overall population and the Japanese subpopulation. CLINICAL TRIAL REGISTRATION: NCT02344004.

Predictive factors of the presence of pulmonary embolism in patients with interstitial lung disease: Observational study.

In patients with interstitial lung disease (ILD), the risk of pulmonary embolism (PE) is increased; however, distinguishing between PE and ILD exacerbation can be difficult. Therefore, this study investigated the usefulness of the Wells criteria and revised Geneva score and predictive factors for diagnosing PE in ILD patients with worsening respiratory symptoms. We retrospectively collected the data of 65 patients with ILD who underwent computed tomography pulmonary angiography at Fukujuji Hospital and Kyorin University Faculty of Medicine from January 2018 to March 2023, including 18 patients in the PE group and 47 patients in the non-PE group, and the data were compared between the 2 groups. The Wells score (P = .165) and revised Geneva score (P = .140) were not useful for distinguishing between the PE and non-PE groups. Patients in the PE group showed higher D-dimer, total protein (TP), and globulin levels than those in the non-PE group (D-dimer median 24.5 µg/mL [range 3.0-79.3] vs 9.3 µg/mL [range 0.5-80.8], P = .016; TP median 7.2 g/dL [range 5.1-8.7] vs 6.4 g/dL [range 5.0-8.2], P = .002; globulin median 3.8 g/dL [range 2.6-5.5] vs 3.2 g/dL [range 3.0-5.3], P = .041). Using cutoff values of TP ≥ 7.0 g/dL and D-dimer ≥ 11.8 µg/mL, the odds ratios for predicting PE were 10.5 and 4.90, respectively. This study demonstrates that high TP and D-dimer levels are useful indicators for predicting PE in ILD patients with worsening respiratory symptoms, while the Wells score and revised Geneva score are not reliable in diagnosing PE.

Video gamers demonstrate superior bronchoscopy skills among beginners.

While previous research has explored the connection between video gaming and medical procedures, studies on the connection between video gaming and bronchoscopy techniques are lacking. This study aimed to investigate how video gaming experience influences bronchoscopy skills, particularly among beginners. This study was conducted at Fukujuji Hospital from January 2021 to October 2023. Twenty-three participants were assigned to the inexperienced group, and eighteen participants were assigned to the experienced group. The observational time during bronchoscopy, measured using a simulator, and the playing time of SPLATOON 2 (NINTENDO Co. Ltd., Japan) were analyzed. Video gaming skills were assessed based on game completion time, with shorter times indicating faster task completion. Participants were also divided into gamer and nongamer subgroups for further comparisons. A moderate linear relationship existed between bronchoscopic observation time and game completion time in the inexperienced group (r = 0.453, p = 0.030). However, no correlation was found in the experienced group (r = 0.268, p = 0.283). Among the inexperienced group, the gamer subgroup (n = 12) exhibited significantly shorter bronchoscopic observation times than did the nongamer subgroup (n = 11) (median [range]: 200 [129-229] s) vs. 281 [184-342] s, p = 0.005). This study demonstrated a relationship between bronchoscopy technique and video gaming skills among individuals with little bronchoscopy experience.

Activities of Daily Living, Hypoxemia, and Lymphocytes Score for Predicting Mortality Risk in Patients With Pulmonary TB.

BACKGROUND: A clinically applicable mortality risk prediction system for pulmonary TB may improve treatment outcomes, but no easy-to-calculate and accurate score has yet been reported. The aim of this study was to construct a simple and objective disease severity score for patients with pulmonary TB. RESEARCH QUESTION: Does a clinical score consisting of simple objective factors predict the mortality risk of patients with pulmonary TB? STUDY DESIGN AND METHODS: The data set from our previous prospective study that recruited patients newly diagnosed with pulmonary TB was used for the development cohort. Patients for the validation cohort were prospectively recruited between March 2021 and September 2022. The primary end point was all-cause in-hospital mortality. Using Cox proportional hazards regression, a mortality risk prediction model was optimized in the development cohort. The disease severity score was developed by assigning integral points to each variate. RESULTS: The data from 252 patients in the development cohort and 165 patients in the validation cohort were analyzed, of whom 39 (15.5%) and 17 (10.3%), respectively, died in the hospital. The disease severity score (named the AHL score) included three clinical parameters: activities of daily living (semi-dependent, 1 point; totally dependent, 2 points); hypoxemia (1 point), and lymphocytes (< 720/µL, 1 point). This score showed good discrimination with a C statistic of 0.902 in the development cohort and 0.842 in the validation cohort. We stratified the score into three groups (scores of 0, 1-2, and 3-4), which clearly corresponded to low (0% and 1.3%), intermediate (13.5% and 8.9%), and high (55.8% and 39.3%) mortality risk in the development and validation cohorts. INTERPRETATION: The easy-to-calculate AHL disease severity score for patients with pulmonary TB was able to categorize patients into three mortality risk groups with great accuracy. CLINICAL TRIAL REGISTRATION: University Hospital Medical Information Network Center; No. UMIN000012727 and No. UMIN000043849; URL: www.umin.ac.jp.

Diagnostic flowchart for tuberculous pleurisy, pleural infection, and malignant pleural effusion.

BACKGROUND: Several markers for the diagnosis of pleural effusion have been reported; however, a comprehensive evaluation using those markers has not been performed. Therefore, this study aimed to develop a diagnostic flowchart for tuberculous pleurisy, pleural infection, malignant pleural effusion, and other diseases by using these markers. METHODS: We retrospectively collected data from 174 patients with tuberculous pleurisy, 215 patients with pleural infection other than tuberculous pleurisy, 360 patients with malignant pleural effusion, and 209 patients with other diseases at Fukujuji Hospital from January 2012 to October 2022. The diagnostic flowchart for four diseases was developed by using several previously reported markers. RESULTS: The flowchart was developed by including seven markers: pleural ADA ≥40 IU/L, pleural fluid LDH <825 IU/L, pleural fluid ADA/TP < 14, neutrophil predominance or cell degeneration, peripheral blood WBC ≥9200/µL or serum CRP ≥12 mg/dL, pleural amylase ≥75 U/L, and the presence of pneumothorax according to the algorithm of a decision tree. The accuracy ratio of the flowchart was 71.7 % for the diagnosis of the four diseases, with 79.3 % sensitivity and 75.4 % positive predictive value (PPV) for tuberculosis pleurisy, 75.8 % sensitivity and 83.2 % PPV for pleural infection, 88.6 % sensitivity and 68.8 % PPV for malignant pleural effusion, and 33.0 % sensitivity and 60.0 % PPV for other diseases in the flowchart. The misdiagnosis ratios were 4.6 % for tuberculosis pleurisy, 6.8 % for pleural infection, and 8.3 % for malignant pleural effusion. CONCLUSION: This study developed a useful diagnostic flowchart for tuberculous pleurisy, pleural infection, malignant pleural effusion, and other diseases.

Impact of primary ciliary dyskinesia: Beyond sinobronchial syndrome in Japan.

Primary ciliary dyskinesia (PCD) is a rare genetic disorder characterized by impaired motile cilia function, particularly in the upper and lower airways. To date, more than 50 causative genes related to the movement, development, and maintenance of cilia have been identified. PCD mostly follows an autosomal recessive inheritance pattern, in which PCD symptoms manifest only in the presence of pathogenic variants in both alleles. Several genes causing PCD have been recently identified that neither lead to situs inversus nor cause definitive abnormalities in ciliary ultrastructure. Importantly, the distribution of disease-causing genes and pathogenic variants varies depending on ethnicity. In Japan, homozygosity for a ∼27.7-kb deletion of DRC1 is estimated to be the most common cause of PCD, presumably as a founder mutation. The clinical picture of PCD is similar to that of sinobronchial syndrome, thus making its differentiation from diffuse panbronchiolitis and other related disorders difficult. Given the diagnostic challenges, many cases remain undiagnosed or misdiagnosed, particularly in adults. While no fundamental cure is currently available, lifelong medical subsidies are provided in Japan, and proper respiratory management, along with continued prevention and treatment of infections, is believed to mitigate the decline in respiratory function. Timely action will be necessary when specific treatments for PCD become available in the future. This narrative review focuses on variations in the disease status of PCD in a non-Western country.

Global Epidemiology of Nontuberculous Mycobacterial Pulmonary Disease: A Review.

Nontuberculous mycobacterial (NTM) isolation and pulmonary disease (NTM-PD) have continued to increase in most regions of the world, driven mainly by Mycobacterium avium. Single-center studies also support increasing trends as well as a persistent burden of undiagnosed NTM among persons suspected of having tuberculosis (TB), in countries with moderate-to-high TB prevalence. Cumulative exposure to water and soil presents an increased risk to susceptible hosts, and trace metals in water supply are recently recognized risk factors. Establishing standard case definitions for subnational and national surveillance systems with mandatory notification of NTM-PD are needed to allow comparisons within and across countries and regions.

FOXJ1 Variants Causing Primary Ciliary Dyskinesia with Hydrocephalus: A Case Report from Japan.

Primary ciliary dyskinesia (PCD) is a genetic disease characterized by motile cilia dysfunction, mostly inherited in an autosomal recessive or X-linked manner. We herein report a 29-year-old woman with PCD caused by a heterozygous frameshift mutation due to a single nucleotide deletion in exon 3 of FOXJ1. Heterozygous de novo mutations in FOXJ1 have been reported as an autosomal-dominant cause of PCD. The patient had situs inversus, congenital heart disease, infertility, and hydrocephalus. However, the nasal nitric oxide level was normal. Long-term macrolide therapy was remarkably effective. This is the first case report of PCD caused by a FOXJ1 variant in Japan.

Analysis of the utility of transbronchial lung biopsy culture under endobronchial ultrasonography with a guide-sheath.

Transbronchial lung biopsy (TBLB) culture is not common in clinical practice, and TBLB culture for patients with mycobacterial disease provide limited value because the diagnostic accuracy of TBLB culture is very low. Recently, bronchoscopic devices have been further developed, such as endobronchial ultrasonography with a guide-sheath (EBUS-GS). Therefore, this study investigated the utility of TBLB culture obtained by using EBUS-GS compared to washing cultures. A total of 31 patients who underwent TBLB culture by using EBUS-GS (GS-TBLB) were collected retrospectively at Fukujuji Hospital from January 2018 to December 2022. The diagnostic accuracies of GS-TBLB culture and bronchial and device washing cultures (namely, washing culture) were compared. The patients comprised 13 individuals with nontuberculous mycobacteriosis, 7 with pulmonary aspergillosis, 6 with lung abscess, and 5 with pulmonary tuberculosis. The diagnostic accuracy of GS-TBLB culture was lower to that of TBLB culture than those of washing culture (n = 11 [35.5%] vs. n = 20 [64.5%], p = 0.016), and there was only one patient with positive GS-TBLB culture results and negative washing culture results. Comparing between patients with mycobacteria and non-mycobacteria, GS-TBLB culture positivity were no significant difference between patients with mycobacteria and non-mycobacteria (n = 6 [33.3%] vs. n = 5 [38.5%], p = 1.000), however, patients with mycobacteria diagnosed by washing culture more than those with non-mycobacteria (n = 15 [83.3%] vs. n = 5 [38.5%], p = 0.021). Our results demonstrate that the utility of TBLB culture for the diagnosis of pulmonary infections might provide limited value even if EBUS-GS is performed and lung tissue is successfully obtained.

Comparison of the thickness of the erector spinae muscles between aspiration pneumonia and bacterial pneumonia patients.

BACKGROUND AND AIMS: Aspiration pneumonia is generally associated with deterioration of skeletal muscle mass, which is usually evaluated by the erector spinae muscle cross-sectional area (ESMCSA); however, no report has assessed ESMCSA in patients with aspiration pneumonia. Furthermore, erector spinae muscle thickness (ESMT) was developed to be easier to measure than ESMCSA. Therefore, this study investigated the relationship between ESMT and ESMCSA in aspiration pneumonia patients compared to bacterial pneumonia patients. METHODS: We retrospectively collected data for 164 patients with aspiration pneumonia and 480 patients with bacterial pneumonia who were hospitalized at Fukujuji Hospital between September 2018 and May 2022. We assessed the correlations between ESMCSA and ESMT and compared the data between the two groups. RESULTS: ESMT had a strong, proportional relationship with ESMCSA in all patients (r = 0.908, p < 0.001) and those with aspiration pneumonia (r = 0.896, p < 0.001). ESMCSA (median 671.8 mm2 [range 164.0-1636.7] vs. median 1057.0 mm2 [range 161.3-2412.5], p < 0.001) and ESMT (median 17.1 mm [range 6.95-34.4] vs. median 23.8 mm [range 6.95-43.7], p < 0.001) were significantly lower in patients with aspiration pneumonia. A multivariate analysis of aspiration pneumonia diagnosis showed significant independent differences from bacterial pneumonia in ESMCSA (odds ratio 0.998 [95% CI: 0.996-0.999], p = 0.001) and ESMT (odds ratio 0.90 [95% CI: 0.84-0.96], p = 0.002). CONCLUSION: This study demonstrates a strong correlation between ESMCSA and ESMT. ESMT can be more easily used to evaluate skeletal muscle mass and can help in diagnosing aspiration pneumonia.

Multiple bacterial culture positivity reflects the severity and prognosis as bronchiectasis in Mycobacterium avium complex pulmonary disease.

BACKGROUND: Bacterial coinfections are observed in 19-66% of patients with Mycobacterium avium complex pulmonary disease (MAC-PD) during the entire duration of the disease. The impact of bacterial coinfection at diagnosis on the clinical course of MAC-PD has not been reported. METHODS: Among 558 patients diagnosed with MAC-PD between January 2016 and December 2020, 218 patients who underwent sputum culture tests twice or more within one year before and after diagnosis were included. We compared the patient characteristics and disease courses between the patients who had the same bacterial species detected twice or more (bacterial culture positive group: BCP group) and those who never had bacteria cultured (bacterial culture negative group: BCN group). RESULTS: We included 70 patients in the BCP group and 74 in the BCN group. The radiological findings showed that BCP at diagnosis correlated with a high modified Reiff score. During the median follow-up period of 42 months, the patients in the BCP group were more likely to accomplish spontaneous sputum conversion of MAC. The treatment initiation rate for MAC-PD in the BCP group was lower than that in the BCN group (41.4% vs. 67.6%, P = 0.003). In contrast, the time to the first bronchiectasis exacerbation in the BCP group was shorter than that in the BCN group, and the frequency of bronchiectasis exacerbations was higher in the BCP group. CONCLUSIONS: Patients with BCP at diagnosis are less likely to initiate treatment for MAC-PD and more likely to develop bronchiectasis exacerbation.

Spontaneous resolution of cryptogenic organizing pneumonia: Observational study.

Cryptogenic organizing pneumonia (COP) is an idiopathic interstitial pneumonia generally requiring steroid therapy, and spontaneous resolution has been reported in patients with mild disease. However, evidence supporting the need for COP treatment is poor. Therefore, we investigated the characteristics of patients with spontaneous resolution. We retrospectively collected data from 40 adult patients who were diagnosed with COP through bronchoscopic examination at Fukujuji Hospital from May 2016 to June 2022. Sixteen patients who improved without steroid therapy (the spontaneous resolution group) and 24 patients who required steroid therapy (the steroid therapy group) were compared. Patients in the spontaneous resolution group showed a lower C-reactive protein (CRP) concentration (median 0.93 mg/dL [interquartile range [IQR] 0.46-1.91] vs median 10.42 mg/dL [4.82-16.7], P < .001), a higher lymphocyte ratio (median 21.7% [18.2-25.2] vs median 13.3% [8.8-19.8], P = .002), and a longer duration from symptom onset to diagnosis of COP (median 51.5 days [24.5-65.3] vs 23.0 days [17.3-31.8], P = .009) than those in the steroid therapy group. Within 2 weeks, all patients in the spontaneous resolution group showed relief of symptoms and alleviated radiographic findings. The area under the receiver operating characteristic (ROC) curve was 0.859 (95% confidence interval [CI]: 0.741-0.978) in CRP. When we arbitrarily determined the cutoff values, including CRP levels of ≤3.79 mg/dL, the sensitivity, specificity, and odds ratio were 73.9%, 93.8%, and 39.8 (95% confidence interval: 4.51-1968.9), respectively. Only 1 patient in the spontaneous resolution group showed recurrence but did not require steroid therapy. Conversely, 4 patients in the steroid therapy group showed recurrence and were treated by an additional course of steroids. The characteristics of COP with spontaneous resolution and factors that determine the patients in whom steroid therapy might be avoided is detailed in this study.

Relationship between the thickness of erector spinae muscles and mortality in patients with pulmonary tuberculosis.

BACKGROUND: Skeletal muscle mass is a known predictor of mortality in older patients. However, its relationship with tuberculosis is unclear. Skeletal muscle mass is determined by the cross-sectional area of erector spinae muscle (ESMCSA). Additionally, the erector spinae muscle thickness (ESMT) is an easier measurement than ESMCSA. This study investigated the relationship of ESMT and ESMCSA with mortality in tuberculosis patients. METHODS: We retrospectively collected the data of 267 older patients (age ≥65 years) who were hospitalized due to tuberculosis at the Fukujuji Hospital from January 2019 to July 2021. This included 40 patients with 60-day mortality (the death group) and 227 patients with 60-day survival (the alive group). Here, we assessed the correlations between ESMCSA and ESMT, and the data were compared between the two groups. RESULTS: ESMT had a strong proportional relationship with ESMCSA (r = 0.991, p < 0.001). ESMCSA (median 670.2 mm2 [interquartile range (IQR): 585.1-760.9] vs. 914.3 mm2 [717.6-1141.6], p < 0.001) and ESMT (median 16.7 mm [15.4-18.6] vs. 21.1 mm [18.0-25.5], p < 0.001) were significantly lower in the patients in the death group than those of patients in the alive group. A multivariable Cox proportional hazard model for 60-day mortality showed significantly independent differences in ESMT (hazard ratio [HR] 0.870 [95% confidence interval (Cl): 0.795-0.952], p = 0.003) and ESMCSA (HR 0.998 [95% Cl: 0.996-0.999], p = 0.009). CONCLUSIONS: This study demonstrated a strong correlation between ESMCSA and ESMT, which were risk factors for mortality in patients with tuberculosis. Therefore, using ESMT is easier to predict mortality than ESMCSA.

In Vitro Synergistic Effects of Omadacycline with Other Antimicrobial Agents against Mycobacterium abscessus.

The clinical importance of Mycobacterium abscessus species (MABS) infections has been increasing. However, the standard treatment regimens recommended in the current guidelines often result in unfavorable outcomes. Therefore, we investigated the in vitro activity of omadacycline (OMC), a novel tetracycline, against MABS to explore its potential as a novel therapeutic option. The drug susceptibilities of 40 Mycobacterium abscessus subsp. abscessus (Mab) clinical strains obtained from the sputum of 40 patients from January 2005 to May 2014 were investigated. The MIC results for OMC, amikacin (AMK), clarithromycin (CLR), clofazimine (CLO), imipenem (IPM), rifabutin (RFB), and tedizolid (TZD) alone and their combined effects (with OMC) were examined using the checkerboard method. Additionally, we studied the differences in the effectiveness of the antibiotic combinations based on the colony morphotype of Mab. The MIC50 and MIC90 of OMC alone were 2 and 4 µg/mL, respectively. The combinations of OMC with AMK, CLR, CLO, IPM, RFB, and TZD showed synergy against 17.5%, 75.8%, 25.0%, 21.1%, 76.9%, and 34.4% of the strains, respectively. Additionally, OMC combined with CLO (47.1% versus 9.5%, P = 0.023) or TZD (60.0% versus 12.5%, P = 0.009) showed significantly higher synergy against strains with rough morphotypes than those with smooth morphotypes. In conclusion, the checkerboard analyses revealed that the synergistic effects of OMC were observed most frequently with RFB, followed by CLR, TZD, CLO, IPM, and AMK. Furthermore, OMC tended to be more effective against rough-morphotype Mab strains.