Sensitivity assessment of diphacinone by pharmacokinetic analysis in invasive black rats in the Bonin (Ogasawara) Archipelago, Japan.

The Bonin Archipelago is a United Nations Educational, Scientific and Cultural Organization's World Natural Heritage Site in Japan with a unique ecosystem; however, the invasive rodents preying on endemic species have been a significant concern. The anticoagulant rodenticide, diphacinone, sprayed by the Ministry of the Environment, has succeeded; however, its repeated use leads to rodenticide resistance. This study evaluated the sensitivity by in vivo pharmacokinetics/pharmacodynamics (PK/PD) analysis and physiologically-based pharmacokinetic modeling to diphacinone in black rats (Rattus rattus) captured on the Bonin Archipelago in February 2022. The Bonin rats exhibited prolonged coagulation time after diphacinone administration. They recovered earlier than susceptible black rats, indicating that Bonin rats were less susceptible, though there were no genetic mutations in Vkorc1, the target enzyme of diphacinone. After the administration of diphacinone, hepatic expression levels of Fsp1, identified as the vitamin K reductase, was decreased, however, the Bonin rats exhibited the most minor suppression. The PK analysis showed that the excretion capacity of the Bonin rats was lower than that of the resistant black rats. In the PBPK modeling, the resistant black rats showed higher clearance than the Bonin and susceptible black rats due to high hepatic metabolic capacity. The Bonin rats demonstrated slow absorption and relatively low clearance. This study highlighted the reduced rodenticide-sensitive tendency of wild black rats in the Bonin Archipelago at an in vivo phenotype level. At the same time, they do not have known rodenticide resistance mechanisms, such as hepatic metabolic enhancement or Vkorc1 mutations. It is crucial to monitor the biological levels to evaluate rodenticide sensitivity accurately.

Increased Oxidative Stress and Decreased Citrulline in Blood Associated with Severe Novel Coronavirus Pneumonia in Adult Patients.

This study investigated the correlation between oxidative stress and blood amino acids associated with nitric oxide metabolism in adult patients with coronavirus disease (COVID-19) pneumonia. Clinical data and serum samples were prospectively collected from 100 adult patients hospitalized for COVID-19 between July 2020 and August 2021. Patients with COVID-19 were categorized into three groups for analysis based on lung infiltrates, oxygen inhalation upon admission, and the initiation of oxygen therapy after admission. Blood data, oxidative stress-related biomarkers, and serum amino acid levels upon admission were compared in these groups. Patients with lung infiltrations requiring oxygen therapy upon admission or starting oxygen post-admission exhibited higher serum levels of hydroperoxides and lower levels of citrulline compared to the control group. No remarkable differences were observed in nitrite/nitrate, asymmetric dimethylarginine, and arginine levels. Serum citrulline levels correlated significantly with serum lactate dehydrogenase and C-reactive protein levels. A significant negative correlation was found between serum levels of citrulline and hydroperoxides. Levels of hydroperoxides decreased, and citrulline levels increased during the recovery period compared to admission. Patients with COVID-19 with extensive pneumonia or poor oxygenation showed increased oxidative stress and reduced citrulline levels in the blood compared to those with fewer pulmonary complications. These findings suggest that combined oxidative stress and abnormal citrulline metabolism may play a role in the pathogenesis of COVID-19 pneumonia.

Identification of exhaled volatile organic compounds that characterize asthma phenotypes: A J-VOCSA study.

BACKGROUND: Asthma is characterized by phenotypes of different clinical, demographic, and pathological characteristics. Identifying the profile of exhaled volatile organic compounds (VOCs) in asthma phenotypes may facilitate establishing biomarkers and understanding asthma background pathogenesis. This study aimed to identify exhaled VOCs that characterize severe asthma phenotypes among patients with asthma. METHODS: This was a multicenter cross-sectional study of patients with severe asthma in Japan. Clinical data were obtained from medical records, and questionnaires were collected. Exhaled breath was sampled and subjected to thermal desorption gas chromatography-mass spectrometry (GC/MS). RESULTS: Using the decision tree established in the previous nationwide asthma cohort study, 245 patients with asthma were divided into five phenotypes and subjected to exhaled VOC analysis with 50 healthy controls (HCs). GC/MS detected 243 VOCs in exhaled breath samples, and 142 frequently detected VOCs (50% of all samples) were used for statistical analyses. Cluster analysis assigning the groups with similar VOC profile patterns showed the highest similarities between phenotypes 3 and 4 (early-onset asthma phenotypes), followed by the similarities between phenotypes 1 and 2 (late-onset asthma phenotypes). Comparisons between phenotypes 1-5 and HC revealed 19 VOCs, in which only methanesulfonic anhydride showed p < 0.05 adjusted by false discovery rate (FDR). Comparison of these phenotypes yielded several VOCs showing different trends (p < 0.05); however, no VOCs showed p < 0.05 adjusted by FDR. CONCLUSIONS: Exhaled VOC profiles may be useful for distinguishing asthma and asthma phenotypes; however, these findings need to be validated, and their pathological roles should be clarified.

Approach/Avoidance Behavior to Novel Objects is Correlated with the Serotonergic and Dopaminergic Systems in the Brown Rat (Rattus norvegicus).

The brown rat (Rattus norvegicus) is known to show three types of behavioral responses to novel objects. Whereas some rats are indifferent to novel objects, neophobic and neophilic rats show avoidance and approach behavior, respectively. Here, we compared the dopaminergic, serotonergic, and noradrenergic systems immunohistochemically among these rats. Trapped wild rats and laboratory rats were first individually exposed to the novel objects in their home cage. Wild rats were divided into neophobic and indifferent rats depending on their behavioral responses. Similarly, laboratory rats were divided into neophilic and indifferent rats. Consistent with the behavioral differences, in the paraventricular nucleus of the hypothalamus, Fos expression in corticotropin-releasing hormone-containing neurons was higher in the neophobic rats than in the indifferent rats. In the anterior basal amygdala, the neophobic rats showed higher Fos expression than the indifferent rats. In the posterior basal amygdala, the neophobic and neophilic rats showed lower and higher Fos expressions than the indifferent rats, respectively. When we compared the neuromodulatory systems, in the dorsal raphe, the number of serotonergic neurons and Fos expression in serotonergic neurons increased linearly from neophobic to indifferent to neophilic rats. In the ventral tegmental area, Fos expression in dopaminergic neurons was higher in the neophilic rats than in the indifferent rats. These results demonstrate that approach/avoidance behavior to novel objects is correlated with the serotonergic and dopaminergic systems in the brown rat. We propose that the serotonergic system suppresses avoidance behavior while the dopaminergic system enhances approach behavior to novel objects.

An immunocompetent case of chronic pulmonary aspergillosis caused by Aspergillusviridinutans.

We encountered an extremely rare immunocompetent case of chronic pulmonary aspergillosis (CPA) caused by Aspergillus viridinutans. A 74-year-old woman was admitted with fever and hemoptysis. Chest computed tomography revealed a nodule in the left upper lobe. Bronchoscopy was performed, and the transbronchial biopsy specimen revealed Aspergillus fungi. Treatment of the nodule was initially ineffective with voriconazole but effective with liposomal amphotericin B. The causative organism was later identified as A. viridinutans based on the gene sequence of ß-tubulin. This is the first immunocompetent case of CPA caused by A. viridinutans.

Pneumocystis jirovecii pneumonia mortality risk associated with preceding long-term steroid use for the underlying disease: A multicenter, retrospective cohort study.

OBJECTIVE: Long-term steroid use increases the risk of developing Pneumocystis pneumonia (PcP), but there are limited reports on the relation of long-term steroid and PcP mortality. METHODS: Retrospective multicenter study to identify risk factors for PcP mortality, including average steroid dose before the first visit for PcP in non-human immunodeficiency virus (HIV)-PcP patients. We generated receiver operating characteristic (ROC) curves for 90-day all-cause mortality and the mean daily steroid dose per unit body weight in the preceding 10 to 90 days in 10-day increments. Patients were dichotomized by 90-day mortality and propensity score-based stabilized inverse probability of treatment weighting (IPTW) adjusted covariates of age, sex, and underlying disease. Multivariate analysis with logistic regression assessed whether long-term corticosteroid use affected outcome. RESULTS: Of 133 patients with non-HIV-PcP, 37 died within 90 days of initial diagnosis. The area under the ROC curve for 1-40 days was highest, and the optimal cutoff point of median adjunctive corticosteroid dosage was 0.34 mg/kg/day. Past steroid dose, underlying interstitial lung disease and emphysema, lower serum albumin and lower lymphocyte count, higher lactate dehydrogenase, use of therapeutic pentamidine and therapeutic high-dose steroids were all significantly associated with mortality. Underlying autoimmune disease, past immunosuppressant use, and a longer time from onset to start of treatment, were associated lower mortality. Logistic regression analysis after adjusting for age, sex, and underlying disease with IPTW revealed that steroid dose 1-40 days before the first visit for PcP (per 0.1 mg/kg/day increment, odds ratio 1.36 [95% confidence interval = 1.16-1.66], P<0.001), low lymphocyte counts, and high lactate dehydrogenase revel were independent mortality risk factor, while respiratory failure, early steroid, and sulfamethoxazole/trimethoprim for PcP treatment did not. CONCLUSION: A steroid dose before PcP onset was strongly associated with 90-day mortality in non-HIV-PcP patients, emphasizing the importance of appropriate prophylaxis especially in this population.

Cough variant and cough-predominant asthma are major causes of persistent cough: a multicenter study in Japan.

OBJECTIVE: Persistent cough is a frequent cause of doctor and hospital visits, and its incidence may be increasing. However, diagnosis of the cause of cough remains difficult. Because different causes of cough have different treatments, accurate diagnosis of the cause of cough is critical. To gain a better understanding of the causes of cough in Japan, we performed a multicenter epidemiological study of Japanese patients. METHODS: The study involved seven institutions in five different areas of Japan, and was conducted over 1 year from March 2009. Patients aged ≥16 years attending the participating centers for the first time complaining of cough persisting for ≥3 weeks were eligible. Patients with chest X-ray abnormalities responsible for cough, fever or blood-stained sputum were excluded, while those with wheeze or shortness of breath were included. Frequency and severity of cough were assessed using questionnaires, and laboratory tests were performed to enable differential diagnoses. RESULTS: Among the 313 patients evaluated, mean duration of cough symptoms was 192.1 ± 558.4 days. Cough variant asthma (CVA) was the most common cause of prolonged/chronic cough (42.2%), followed by cough-predominant asthma (CPA) (28.4%), atopic cough (7.3%) and chronic obstructive pulmonary disease (6.7%). Patients with an unclear diagnosis were treated with tulobuterol, a transdermal ß2-agonist preparation, for 1-2 weeks. Transdermal tulobuterol improved assessments of cough in patients with CVA or CPA, enabling rapid diagnosis of these diseases. CONCLUSIONS: These findings show that CVA and CPA are the main causes of cough persisting for ≥3 weeks.

Hypoallergenicity and immunological characterization of enzyme-treated royal jelly from Apis mellifera.

Royal jelly (RJ), the exclusive food for queen bees, is taken as a dietary supplement because it is highly rich in nutrients. However, RJ is known to induce an anaphylactic response in some individuals. We evaluated in the present study the hypoallergenicity of alkaline protease-treated RJ in vitro and in vivo. We first confirmed that this treated RJ contained the same levels of vitamins, minerals and specific fatty acid as in untreated RJ. We then showed that the IgE-binding capacity of the treated RJ was very significantly reduced by conducting in vitro assays of the blood from RJ-sensitive patients. An in vivo skin-prick test on the RJ-sensitive patients also showed that, in the majority of the patients (3 out of 4 tested), the treated RJ did not evoke any allergenic response. It is thus advantageous to prepare hypoallergenic RJ by a protease enzyme treatment for its safe consumption.

Radiation-Induced Lung Injury With Lung Cancer Treated With the Combination Therapy of Nintedanib and Dexamethasone.

Radiation-induced lung injury (RILI) associated with lung cancer becomes refractory. Nintedanib is a multi-kinase inhibitor that suppresses the development of pulmonary fibrosis. Herein, we report a case of RILI with progressive pulmonary fibrosis after stereotactic body radiation therapy in a 70-year-old man with lung cancer. The patient responded well to the initial prednisolone therapy but became resistant during tapering. The combination therapy of nintedanib and dexamethasone resulted in a temporary improvement in RILI. Nintedanib is not a standard therapy for RILI, and further investigation is needed to evaluate the effects of nintedanib on RILI complicated by lung cancer.

Switching to Dupilumab from Other Biologics without a Treatment Interval in Patients with Severe Asthma: A Multi-Center Retrospective Study.

BACKGROUND: Dupilumab is a fully humanized monoclonal antibody that blocks interleukin-4 and interleukin-13 signals. Several large clinical trials have demonstrated the efficacy of dupilumab in patients with severe asthma. However, few studies have examined a switch to dupilumab from other biologics. METHODS: This retrospective, multi-center observational study was conducted by the Okayama Respiratory Disease Study Group. Consecutive patients with severe asthma who were switched to dupilumab from other biologics without a treatment interval between May 2019 and September 2021 were enrolled. Patients with a treatment interval of more than twice the standard dosing interval for the previous biologic prior to dupilumab administration were excluded. RESULTS: The median patient age of the 27 patients enrolled in this study was 57 years (IQR, 45-68 years). Eosinophilic chronic rhinosinusitis (ECRS)/chronic rhinosinusitis with nasal polyp (CRSwNP) was confirmed in 23 patients. Previous biologics consisted of omalizumab (n = 3), mepolizumab (n = 3), and benralizumab (n = 21). Dupilumab significantly improved FEV1 (median improvement: +145 mL) and the asthma control test score (median improvement: +2). The overall response rate in patients receiving dupilumab for asthma as determined using the Global Evaluations of Treatment Effectiveness (GETE) was 77.8%. There were no significant differences in the baseline characteristics of the GETE-improved group vs. the non-GETE-improved group. ECRS/CRSwNP improved in 20 of the 23 patients (87.0%). Overall, 8 of the 27 patients (29.6%) developed transient hypereosinophilia (>1500/µL), but all were asymptomatic and able to continue dupilumab therapy. CONCLUSIONS: Dupilumab was highly effective for the treatment of severe asthma and ECRS/CRSwNP, even in patients switched from other biologics without a treatment interval.

[Clinical effects of Lactobacillus acidophilus strain L-55-contained yogurt on symptoms of Japanese cedar pollen allergy].

BACKGROUND: It has been reported that oral administration of Lactobacillus acidophilus strain L-55 (L-55) suppressed nasal symptom and antigen-specific IgE induced by antigen challenge in mice. We investigated clinical effects of L-55-contained yogurt on symptoms and IgE production in the patients with Japanese cedar pollinosis. METHOD: The study was performed as a randomized double blind placebo-controlled trial. L-55-contained yogurt (L-55 yogurt) or placebo yogurt was started to administer to each subject from 4 weeks prior to the onset of Japanese cedar pollen release for total 13 weeks. RESULT: The mean value of symptom score and symptom medication score were lower in L-55 yogurt group compared with placebo yogurt group during 5th week to 9th week from the first week of Japanese cedar pollination. Especially, in medicated subjects, total symptom score and throat symptom score were significantly lower in L-55 yogurt group compared with placebo yogurt group at 5th and 4th week from the first week of Japanese cedar pollination, respectively. Moreover, in medicated subjects, change ratio of serum total IgE was significantly lower in L-55 yogurt group compared with placebo yogurt group at 1st week from the first week of Japanese cedar pollination. CONCLUSION: Intake of L-55 during Japanese cedar pollinating season may be effective in alleviating the allergic symptoms related to Japanese cedar pollinosis. From these finding, it was suggested that L-55 is a possible candidate as a complementary medicine for Japanese cedar pollinosis.

Pneumonia Caused by Community-Acquired Methicillin-Resistant Staphylococcus aureus Positive for Exfoliative Toxin A and Secondary to Allergic Bronchopulmonary Aspergillosis.

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) causes severe pneumonia. Previous reports found that CA-MRSA producing the Panton-Valentine leukocidin (PVL) or toxic shock syndrome toxin-1 (TSST-1) triggered severe necrotizing pneumonia. However, other toxins and genetic factors responsible for CA-MRSA pneumonia are rarely analyzed in Japan. In this study, we performed whole-genome sequencing (WGS) to analyze the clinical features of CA-MRSA genetically. As a result, we identified a strain with a rare sequence-type of MRSA. Herein, we present a case of CA-MRSA pneumonia in a 64-year-old woman. Her condition improved rapidly with vancomycin therapy. Draft WGS led to identifying the genotype and virulence factors and showed that the strain was a rare sequence-type of MRSA with the following characteristics: staphylococcal cassette chromosome mec (SCCmec) type IV, sequence type 121, exfoliative toxin A-positive, and specific staphylococcal protein A type t5110. To the best of our knowledge, a strain with this profile has not been previously reported. Our findings provide new insights into CA-MRSA pneumonia and its genetic and clinical features. Therefore, we recommend accumulating genetic profiles of CA-MRSA pneumonia to identify genetic features and the clinical characteristics of the patients.

A Fast-growing Benign Metastasizing Leiomyoma Mimicking Malignancy.

We herein report a rare case of fast-growing benign metastasizing leiomyoma. A 52-year-old woman was admitted to our hospital with abnormal chest shadows. Chest computed tomography showed well-circumscribed cystic tumors. Because malignancy could not be completely distinguished in fast-growing tumors, video-assisted thoracic surgery was performed. The pathological findings revealed many cysts and the proliferation of smooth muscle cells. According to the Stanford criteria, the tumor was diagnosed as benign metastasizing leiomyoma. One possible reason for the fast growth of the tumor was enlargement of the cysts. Malignant diseases characterized by cystic tumors are rare but occasionally reported. Therefore, differentiation by a pathological examination is essential.

A case of nonmucinous pulmonary micropapillary adenocarcinoma mimicking pulmonary tuberculosis.

We report a rare case of nonmucinous pulmonary micropapillary adenocarcinoma mimicking pulmonary tuberculosis. A 68-year-old woman was hospitalized with hemoptysis. Her computed tomography revealed cavities and tree-in-bud appearance similar to the extensive form of pulmonary tuberculosis. However, histopathological findings of transbronchial biopsies of all lesions revealed adenocarcinoma and no pulmonary tuberculosis. Tree-in-bud appearance may relate to the floating micropapillary tufts in alveolar spaces. If pulmonary carcinoma is complicated by pulmonary tuberculosis, patients must be isolated and disadvantaged in cancer treatments. Therefore, recognizing this case may be therapeutically useful for respiratory physicians treating both diseases.

[The relationships between the peak inspiratory flow and the characteristics factors in the asthmatics with inhaled corticosteroid -a multicenter study in Chugoku Shikoku area].

BACKGROUND: Inhaled corticosteroid (ICS) will be effective if used properly. Inadequate intake may result in insufficiency, such as for elderly asthmatics, in particular, for use of dry powder inhalers. METHODS: 312 asthmatics treated with ICS for at least 6 months in the 6 facilities belonging to the Chugoku Shikoku Adult Asthma Research Forum were subject to investigation of the peak inspiratory flow (PIF) measured using In-check® and related factors. RESULTS: Nine (2.8%) patients were considered to have insufficient intake. By multivariate analysis, PIF (L/min) prediction formula was as follows: 79.0+0.19* peak expiratory flow (PEF: L/min)+22.9* FVC (L)-0.68* onset age (years)+34.7* gender (male, 1; female, 0)+16.1* V50/V25, [r^2=0.677, p<0.0001]. Using cluster analysis with Euclidean distance and Ward's method, the PIF without an adaptor was included in the same category as height and PEF, and the PIF with an adaptor was included in the same category as %FVC and %FEV1.0. CONCLUSION: The cases with insufficient PIF are few but present. Adequate device selection and inhalation guidance may be important. The meaning of PIF differs depending on whether or not an adaptor is present. Further investigation of intake is considered necessary.

Existence of wild brown rats (Rattus norvegicus) that are indifferent to novel objects.

Exposure to novel objects typically evokes avoidance behavior in wild animals, which is called neophobia. We previously found that wild brown rats (Rattus norvegicus) that were trapped in a park in downtown Tokyo, Japan, exhibited neophobia. We also found that this behavior was accompanied by the activation of the basolateral complex of the amygdala (BLA). Previous studies have suggested that genetic factors are the primary determinants of neophobia. Since rats in cities form populations with distinct genetic characteristics, it is reasonable to assume that wild rats caught at different locations in urban centers will exhibit different levels of neophobia. Here we assessed the intensity of neophobia in wild rats trapped at a wholesale market in Tokyo. Although we performed exactly the same experiment in which neophobia was observed in wild rats trapped at the park, the presence of novel objects did not affect the behaviors of wild rats trapped at the market. Conversely, laboratory rats showed approach and exploratory behaviors as seen in the previous study, suggesting that the experiment was performed appropriately. Compared to the laboratory rats, the lack of behavioral changes in the wild rats was accompanied by fewer Fos immunoreactive cells in the BLA. In addition, the numbers of Fos immunoreactive cells in the bed nucleus of the stria terminalis and ventromedial hypothalamus were similar between the two types of rats. The results demonstrated the existence of wild rats that were indifferent to novel objects.

PaO2-guided Low-dose Oxygen Therapy for Pneumatosis Cystoides Intestinalis to Prevent Acute Exacerbation of Interstitial Pneumonia.

We herein report the first case of low-dose oxygen therapy for pneumatosis cystoides intestinalis (PCI) using PaO2 as a therapeutic index to prevent acute exacerbation of interstitial pneumonia. An 86-year-old man was admitted to our hospital with abdominal distension. PCI was diagnosed by abdominal computed tomography. Low-dose oxygen therapy was started to avoid acute exacerbation of interstitial pneumonia. The oxygen dose was adjusted so that the PaO2 value was approximately 100 mmHg. After seven days of treatment, the colon gas had disappeared, and no acute exacerbation of interstitial pneumonia was observed. A PaO2 value around 100 mmHg is effective for PCI without inducing acute exacerbation of interstitial pneumonia.

Successful Treatment of Antifungal Combination Therapy with Inhaled Liposomal Amphotericin B and Oral Voriconazole for Intractable Chronic Progressive Pulmonary Aspergillosis.

We experienced a case of the successful treatment of intractable pulmonary aspergillosis with inhaled liposomal amphotericin B (L-AMB) and oral voriconazole (VRCZ). A 52-year-old man was admitted to our hospital with a fever. Chest computed tomography (CT) revealed an infiltrative shadow. Two separate sputum cultures detected Aspergillus niger. Although we treated the patient with single and combined antifungal agents, the infiltrative shadow worsened. After obtaining sufficient informed consent from the patient, we switched him to an inhaled L-AMB. The infiltrative shadow subsequently improved. The patient has remained well for one year without exacerbation. We herein report the usefulness of inhaled L-AMB and oral VRCZ.

Interstitial Pneumonia Secondary to Hermansky-Pudlak Syndrome Type 4 Treated with Different Antifibrotic Agents.

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive hereditary disease that may be complicated by progressive and potentially fatal interstitial pneumonia. We herein report a 64-year-old woman with interstitial pneumonia associated with HPS type 4 whom we treated with nintedanib after pirfenidone proved ineffective. To our knowledge, there have been no previous reports of nintedanib being used to treat a patient with HPS type 4. There is a need for clinical trials of antifibrotic agents, including nintedanib, pirfenidone, and new therapeutic agents with different mechanisms of action in these patients.

Solitary pulmonary nodules caused by Mycobacterium avium complex.

BACKGROUND: The prevalence of Mycobacterium avium complex (MAC) pulmonary disease (PD) is increasing significantly in Japan. Among the patterns of MAC-PD, a solitary pulmonary nodule (SPN) is less common and often resembles lung cancer. The aim of this study was to identify the clinical features of MAC-SPN. METHODS: SPNs culture-positive for MAC (definite cases) and culture-negative SPNs showing nucleic acid amplification test (NAAT)-positive status (probable cases) that presented between January 2007 and December 2017 were enrolled. The patients' clinical, laboratory, radiological, and microbiological findings and outcomes were investigated. RESULTS: This study included 28 patients (median age, 66 years; 16 men, 12 women). All patients were asymptomatic when the disease was detected. Median SPN size was 23.5 mm. Twenty-six patients underwent video-assisted thoracoscopic surgery, while the others underwent percutaneous needle biopsy for diagnosis. Granulomatous inflammation was confirmed in all cases. Microbiologically, the 28 cases were divided into 17 in the definite group and 11 in the probable group. In both groups, M. avium was predominant. There were no significant differences in clinical and radiological findings and follow-up periods between the 2 groups. After diagnosis, 6 patients received medical treatment, while the others did not. The median follow-up period was 42 months, and no recurrence was observed in both groups. CONCLUSIONS: MAC should be considered in the differential diagnosis of SPNs in asymptomatic patients. To overcome the difficulties in diagnosing MAC-SPN, this study underscores the importance of diagnostic interventions and identification of MAC by culture and/or NAAT in biopsied specimens.