Characteristics of pulmonary Mycobacterium avium-intracellulare complex (MAC) infection in comparison with those of tuberculosis

Diagnosis of mycobacterium avium complex infection utilizing metagenomics next-generation sequencing: a case report

Mycobacterium avium-intracellulare complex (MAC) is a type of nontuberculous mycobacteria (NTM) and is associated with underlying pulmonary diseases, such as chronic obstructive pulmonary disease, bronchiectasis, chronic aspiration or recurrent pneumonia, inactive or active tuberculosis, pneumoconiosis, and bronchogenic carcinoma. The risk factors for NTM-PD include host, drug, and environmental factors. In this report, we present the case of a 61-year-old man who developed bilateral lung nodules and was experiencing severe hemoptysis. The repeat acid-fast bacilli test performed on both sputum and bronchoalveolar lavage fluid (BALF) samples showed a negative result, as did the GeneXpert test. We employed metagenomic next-generation sequencing (mNGS) to analyze the lung nodule and BALF samples collected from the patient. Both samples tested positive for MAC within 3 days. In addition, traditional MAC culture, conducted for 2 months, confirmed the growth of MAC in the patient's BALF. Then, the patient was treated accordingly. Following treatment, a high-resolution chest computed tomography scan revealed a significant reduction in lung nodules of the patient after 2 months. These results indicate that MAC-associated lung nodules were responsible for the patient's symptoms, emphasizing the need for vigilance in diagnosing MAC infection in the patient without predisposing conditions. Furthermore, these results highlight the potential utility of mNGS as a promising rapid diagnostic tool for MAC infection and its potential role in the diagnosis of NTM disease.

Mycobacterium avium Complex Disease

Despite the ubiqitous nature of Mycobacterium avium complex (MAC) organisms in the environment, relatively few of those who are infected develop disease. Thus, some degree of susceptibility due to either underlying lung disease or immunosuppression is required. The frequency of pulmonary MAC disease is increasing in many areas, and the exact reasons are unknown. Isolation of MAC from a respiratory specimen does not necessarily mean that treatment is required, as the decision to treatment requires the synthesis of clinical, radiographic, and microbiologic information as well as a weighing of the risks and benefits for the individual patient. Successful treatment requires a multipronged approach that includes antibiotics, aggressive pulmonary hygiene, and sometimes resection of the diseased lung. A combination of azithromycin, rifampin, and ethambutol administered three times weekly is recommend for nodular bronchiectatic disease, whereas the same regimen may be used for cavitary disease but administered daily and often with inclusion of a parenteral aminoglycoside. Disseminated MAC (DMAC) is almost exclusively seen in patients with late-stage AIDS and can be treated with a macrolide in combination with ethambutol, with or without rifabutin: the most important intervention in this setting is to gain HIV control with the use of potent antiretroviral therapy. Treatment outcomes for many patients with MAC disease remain suboptimal, so new drugs and treatment regimens are greatly needed. Given the high rate of reinfection after cure, one of the greatest needs is a better understanding of where infection occurs and how this can be prevented.

Elevated serum CA 19-9 levels in patients with pulmonary nontuberculous mycobacterial disease

Increased serum CA 19-9 levels in patients with nonmalignant diseases have been investigated in previous reports. This study evaluates the clinical significance of serum CA 19-9 elevation in pulmonary nontuberculous mycobacterial disease and pulmonary tuberculosis. The median CA 19-9 level was higher in patients with pulmonary nontuberculous mycobacterial disease than in patients with pulmonary tuberculosis (pulmonary nontuberculous mycobacterial disease: 13.80, tuberculosis: 5.85, p < 0.001). A multivariate logistic regression analysis performed in this study showed that Mycobacterium abscessus (OR 9.97, 95% CI: 1.58, 62.80; p = 0.014) and active phase of pulmonary nontuberculous mycobacterial disease (OR 12.18, 95% CI: 1.07, 138.36, p = 0.044) were found to be risk factors for serum CA 19-9 elevation in pulmonary nontuberculous mycobacterial disease. The serum CA 19-9 levels showed a tendency to decrease during successful treatment of pulmonary nontuberculous mycobacterial disease but not in pulmonary tuberculosis. These findings suggest that CA 19-9 may be a useful marker for monitoring therapeutic responses in pulmonary nontuberculous mycobacterial disease, although it is not pulmonary nontuberculous mycobacterial disease-specific marker.

Evaluation and management of patients with pulmonary nontuberculous mycobacterial infections

Nontuberculous mycobacteria (NTM) are emerging pathogens increasingly associated with chronic pulmonary disease. NTM are environmental saprophytes found in soil, dust and water and, unlike Mycobacterium tuberculosis, NTM are not transmitted from person to person. Pulmonary disease caused by NTM is a particular problem in older people without underlying immune compromise. The diagnosis of NTM pulmonary disease usually requires either multiple respiratory cultures that grow NTM or heavy growth of NTM from a single bronchoscopy or lung-biopsy specimen. High resolution computed tomography is the most useful radiographic study for diagnosis and to determine the extent of disease. Treatment includes multiple medications with activity against the particular NTM species, as single-drug therapy is likely to select for resistant organisms. Data demonstrating the effectiveness of specific drug regimens for NTM pulmonary disease are limited. Clarithromycin and azithromycin form the backbone of most treatment regimens because these drugs are active against many NTM species. Drug tolerability and cost are the major barriers to successful treatment of NTM pulmonary disease. Adjunctive therapies, including mucus clearance techniques and appetite stimulants, are unproven but may be of value in management of NTM pulmonary disease. Multicenter, randomized trials of macrolide-based therapies are sorely needed to determine the safest and most effective treatments for NTM pulmonary disease.

Extremely increased serum carbohydrate antigen 19-9 levels caused by new or resistant infections to previous antibiotics in chronic lung diseases

In this paper, we describe 72-year-old female patient without evidence of malignant disease presented with significantly elevated serum carbohydrate antigen (CA) 19-9 levels by respiratory infections. She was diagnosed with respiratory infections due to Mycobacterium avium complex and Pseudomonas aeruginosa. The serum CA 19-9 levels remarkably increased (1,453-5,300 U/mL; reference range, <37 U/mL) by respiratory infection and abruptly decreased (357-534 U/mL) whenever infection was controlled by specific treatments. This case suggests that serum CA 19-9 levels may be used as a diagnostic marker to indicate new or resistant infections to previous antibiotics in chronic lung diseases without significant changes in chest X-ray findings.

Atypical mycobacterium detection in refractory chronic rhinosinusitis

OBJECTIVES

Atypical mycobacterium (AM) involvement in refractory chronic rhinosinusitis (CRS) is sought by some surgeons with customary acid-fast bacilli cultures (AFBC) in the operating room (OR). We evaluate our experience with AM in CRS by describing (1) associated risk factors, (2) species identified, and (3) frequency of positive cultures in clinic versus OR.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary rhinology practice.

SUBJECTS AND METHODS

AFBC taken between 2005 and 2011 were identified from a microbiology laboratory database. Charts were reviewed for gender, age, medical history, risk factors for AM, pathogen types, and treatments, with statistical comparison using Pearson χ(2). The benefit of "targeted AFBC" for cases with high clinical suspicion was compared with "customary AFBC" in the OR.

RESULTS

Thirty-seven patients were identified with AM, of which 10 had one or more risk factors for AM including foreign body (n = 4), non-HIV immune dysfunction (n = 4), and previous chemoradiation (n = 4). Six different AM species were identified: most frequently Mycobacterium abscessus (57.1%), followed by Mycobacterium avium-intracellulare complex (14.3%) and Mycobacterium chelonae (14.3%). "Targeted AFBC" from the outpatient setting were positive in 10 of 190 (5.3%) patients, whereas 10 of 373 (2.6%) patients of "customary AFBC" in the OR were positive (P = .12). Macrolide therapy was employed in 23 of 37 (62%) patients with AM-associated CRS but was not prescribed in patients with positive "customary AFBC" alone.

CONCLUSION

AM-associated CRS is an uncommon condition that can occur in the absence of foreign body or overtly altered innate/adaptive immunity. Indications and efficacy of macrolide therapy, as well as the potential relationships between existence of AM in tap water, AM biofilms, and frequent use of nasal irrigations warrant further investigation in refractory CRS.

Increased CA 19-9 level in patients without malignant disease

BACKGROUND

The measurement of carbohydrate antigen 19-9 (CA 19-9) is recommended for the diagnosis and follow-up of pancreatic cancer. However, increased CA 19-9 has also been reported in patients with various benign diseases of the lung. We aimed to elucidate the pulmonary radiographic abnormalities and laboratory results associated with increased concentrations of CA 19-9.

METHODS

This study was performed using a case-controlled design. Cases included all participants in a cancer screening program who had an increased CA 19-9 concentration (>37 U/mL), but without a diagnosis of malignancy. Age- and sex-matched participants with normal CA 19-9 levels were enrolled as controls. Laboratory results and radiographic features were compared.

RESULTS

In total, 119 participants with increased CA 19-9 concentrations and 476 controls were included. A higher erythrocyte sedimentation rate (ESR) [adjusted odd ratio (aOR), 1.03; 95% confidence interval (CI), 1.01-1.05], higher hemoglobin A(1c) (HbA(1c)) (aOR, 1.28; 95% CI, 1.05-1.56), bronchiectasis (aOR, 2.48; 95% CI, 1.22-5.02), bronchiolitis (aOR, 3.93; 95% CI, 1.88-8.22), emphysema (aOR, 2.67; 95% CI, 1.32-5.40), and interstitial fibrosis (aOR, 10.62; 95% CI, 2.03-55.44) were independent factors for increased CA 19-9.

CONCLUSIONS

CA 19-9 concentrations, as well as increased ESR and HbA(1c), can be increased in patients with various lung abnormalities.

Mycobacterium avium complex pulmonary disease in patients without HIV infection

Mycobacterium avium complex (MAC) is ubiquitous. It is found in various freshwater and saltwater sources around the world, including hot water pipes. Although the organism was identified in the 1890s, its potential to cause human disease was only recognized 50 years later. Only a minority of people exposed to the organism will acquire MAC lung disease, usually those with underlying lung disease or immunosuppression. MAC may, however, cause progressive parenchymal lung disease and bronchiectasis in patients without underlying lung disease, particularly in middle-aged and elderly women. Preliminary data suggest that the interferon-gamma pathways may be deficient in elderly women with MAC lung disease. Other groups of patients who are more likely to harbor MAC in their lungs include patients with a cystic fibrosis or an abnormal alpha(1)-antiproteinase gene and patients with certain chest wall abnormalities. Treatment results continue to be disappointing, and the mortality of patients with MAC lung disease remains high. A PubMed search identified 38 reports of the treatment of MAC lung disease. Apart from the British Thoracic Society study, the only published controlled investigation, the studies published since 1994 have included a macrolide, either clarithromycin or azithromycin, usually in combination with ethambutol and a rifamycin. If success is defined as eradication of the organism without relapse over a period of several years after treatment has been discontinued, the reported treatment success rate with the macrolide containing regimens is approximately 55%. The prolonged treatment period, side effects, and possibly reinfection rather than relapse are responsible for the high failure rate.