Diagnosis and treatment of pulmonary diseases caused by Mycobacterium avium complex

Recently, the clinical importance of non-tuberculous mycobacteria(especially, Mycobacterium avium complex [MAC] respiratory infection) has been increasing. In addition, an official ATS/IDSA statement about diagnosis, treatment, and prevention of nontuberculous mycobacterial diseases has been published in February, 2007. In this review article, clinical features and radiological findings of pulmonary MAC diseases mainly i) primarily fibrocavitary disease, and ii) nodular/bronchiectatic disease are described. Primarily fibrocavitary disease is characterized by cavitary lesions in upper lung fields in elderly subjects, smoking patients, or patients with pneumoconiosis. Nodular/bronchiectatic disease is characterized by centrilobular nodules and diffuse bronchiectases in the right middle lobe and the left lingula in middle-aged women. In addition, diagnosis and treatment for pulmonary diseases caused by MAC are also described.     

Clinicopathologic characteristics of nontuberculous mycobacterial lung disease in Taiwan

Taiwan is an endemic area for tuberculosis (TB), and the incidence of pulmonary infection caused by nontuberculous mycobacteria (NTMs) is also increasing. This study aims to investigate the clinicopathologic characteristics of patients with NTM lung disease during 1998 to 2007 at a medical center in Taiwan. The medical records of patients with confirmed NTM pulmonary infections who underwent open lung surgery in a medical center were reviewed. Twenty-four patients with confirmed NTM pulmonary infections were identified. These patients were histologically classified into 4 types: fibrocavitary/tuberculoid (n = 10), nodular bronchiectatic (n = 4), sarcoidal (n = 6), and other (n = 4). The fibrocavitary/tuberculoid type usually (90%) develops in the upper lobes of old patients with preexisting lung disease. Pulmonary TB (n = 7, 70%) was the major underlying disease before 2003. Nodular bronchiectatic type occurred mainly in the middle lobe of middle-aged women without preexisting lung disease. Sarcoidal type was usually associated with Mycobacterium avium complex infection and develops in middle-aged women. Immunoreactive bacilli were detected in 21 patients (87 %) by immunohistochemical staining using a polyclonal antibody against Mycobacterium tuberculosis and other mycobacterial species (M. avium-intracellulare, Mycobacterium phlei, and Mycobacterium parafortuitum), whereas conventional acid-fast staining was positive in only 21% of patients. In conclusion, TB was the major underlying disease in patients with NTM lung disease in Taiwan. The different histologic types of pulmonary NTM infection suggest each had a distinct pathogenesis.     

Treatment outcomes of refractory MAC pulmonary disease treated with drugs with unclear efficacy

We aimed to investigate the treatment outcomes of patients with refractory Mycobacterium avium complex (MAC) lung disease treated with regimens containing drugs with unclear efficacy. Of all patients diagnosed with MAC lung disease between April 2004 and September 2012 at a tertiary referral center in South Korea, the outcomes of 51 patients treated with regimens containing drugs with unclear efficacy (clofazimine, moxifloxacin, rifabutin, and linezolid) because of treatment failure after receiving standard treatment were retrospectively analyzed. The mean age (standard deviation) of the 51 patients was 59.0 (10.3) years and 29 (56.9%) were male. The etiologic agent was M. avium in 17 patients (33.3%) and Mycobacterium intracellulare in 34 patients (66.7%); 42 patients (82.4%) had the fibrocavitary form of the disease. Of the 51 patients, 26, 28, 35, and 7 received clofazimine-, moxifloxacin-, rifabutin-, and linezolid-containing regimens (numbers are not mutually exclusive), with median drug administration durations of 147, 128, 209, and 88 days, respectively. Overall, 8 patients (15.7%) had a favorable response. Treatment outcomes did not differ by drug regimen or even by the combination of more than 2 drugs. The treatment outcomes of patients with refractory MAC lung disease were unsatisfactory with regimens containing possibly effective drugs such as clofazimine, moxifloxacin, rifabutin and linezolid.     

The pathophysiological concept of nontuberculous mycobacterial diseases and pulmonary Mycobacterium avium complex disease

Although nontuberculous mycobacteria (NTM) were initially isolated shortly after Mycobacterium tuberculosis, it has not been confirmed as true human pathogens until the 1930s. Only around 30 NTMs among more than 150 identified can infect to human, and cause pulmonary, lymph node, skin, soft tissue, bone, and disseminated diseases. NTM diseases, especially pulmonary, appear to be increasing all over the world. M. avium complex (MAC) and M. kansasii were the most frequent pulmonary pathogens. There are three forms in MAC respiratory infection; "fibrocavitary", "nodular/bronchiectatic" and "hot tub lung". Fibrocavitary form prefers apical bulla and cavity by pre-existing disease in smoking males. Nodular/bronchiectatic form involves middle lobe or lingula predominantly in non-smoking females. There must be the genetic susceptibility, but details are unknown.     

Response to Switch from Intermittent Therapy to Daily Therapy for Refractory Nodular Bronchiectatic Mycobacterium avium Complex Lung Disease

Intermittent three-times-weekly antibiotic therapy is recommended for the initial treatment of patients with noncavitary nodular bronchiectatic Mycobacterium avium complex lung disease. Although some experts recommend switching from intermittent to daily therapy for patients whose sputum has persistent positive cultures after intermittent therapy, the clinical efficacy of these modifications is unknown. Of 20 patients whose sputum had persistent positive cultures after 12 months of intermittent antibiotic therapy, specimens from 6 patients (30%) achieved a negative culture after a change to daily therapy.     

Efficacy and safety of intermittent maintenance therapy after successful treatment of Mycobacterium avium complex lung disease

Background

The optimal duration of antimicrobial therapy for Mycobacterium avium complex lung disease (MAC-LD) is unknown, and recurrence rates are high after treatment discontinuation. Intermittent therapy is recommended for the initial treatment of non-cavitary nodular/bronchiectatic MAC-LD. We hypothesized that intermittent maintenance therapy (IMT) could effectively prevent recurrence after successful treatment of MAC-LD.

Clinical characteristics and prevalence of pneumothorax in patients with pulmonary Mycobacterium avium complex disease

Pneumothorax in patients with pulmonary Mycobacterium avium complex (MAC) disease is considered to be a rare complication, and little is known about its clinical course. In this study, we aimed to define the clinical features, outcome, and prevalence of pneumothorax in patients with pulmonary MAC disease. A retrospective review of medical records identified eight men and ten women (mean age, 75 years) with active pulmonary MAC disease complicated by pneumothorax between 2003 and 2010 in our institution. None of the patients was positive for HIV infection. Pneumothorax occurred in the right lung in 12 patients and in the left in six. All but one patient had MAC disease in both lungs, and 12 patients had widespread lesions covering a total area larger than one lung field. Seven of the 18 patients (39 %) were forced to undergo surgery following unsuccessful thoracic drainage. Five patients experienced recurrence during the study period and two others eventually developed chronic pneumothorax. The complication rate of pneumothorax was calculated on the bases of the total number of patients with active pulmonary MAC disease during the same period. The overall complication rate of pneumothorax was as high as 2.4 % (18 of 746 patients with MAC disease). In conclusion, the incidence of pneumothorax in patients with active pulmonary MAC disease was unexpectedly high, especially in patients who were elderly and had advanced MAC disease. This condition is often difficult to treat and can recur easily.     

Treatment outcomes of the interstitial lung disease subtype of unclassifiable type Mycobacterium avium complex pulmonary disease

BackgroundWe aimed to investigate treatment outcomes according to the presence or absence of cavitary lesions in patients with the interstitial lung disease (ILD) subtype of unclassifiable type Mycobacterium avium complex (MAC) pulmonary disease (PD).MethodsStudy subjects were enrolled at a tertiary referral center in South Korea from 2001 to 2020. Among patients with MAC-PD who had ILD as an underlying disease, 38 patients who were diagnosed with the ILD subtype of unclassifiable MAC-PD and who received treatment for ≥1 year were selected for this study. Treatment outcomes in terms of microbiological cure at 1 year were retrospectively analyzed for these patients.ResultsThe mean age of the patients was 64.4 ± 12.9 years, and 63.2% were male. The presence of cavitary lesions was noted in 68.4% (26/38) patients. A usual interstitial pneumonia pattern was the predominant type of ILD, which was identified in 26 (68.4%) patients. The overall 1-year microbiological cure rate of the 38 patients was 65.8% (25/38). Of the 26 patients with cavitary lesions, microbiological cure at 1 year was achieved in 14 patients (53.8%), which is significantly lower than that in patients without cavitary lesions (91.7%, 11/12, p = 0.030).ConclusionsA clear difference in treatment outcomes was noted in the ILD subtype of MAC-PD according to the presence or absence of cavitary lesions.     

Differences in drug susceptibility pattern between Mycobacterium avium and Mycobacterium intracellulare isolated in respiratory specimens

Mycobacterium avium complex (MAC) is the most common etiologic organisms of nontuberculous mycobacteria (NTM) lung disease. In this study, we aimed to retrospectively investigate the differences in drug susceptibility patterns of two major MAC species; Mycobacterium avium and Mycobacterium intracellulare. A total of 1883 major two MAC isolates (1060 M. avium and 823 M. intracellulare) from respiratory specimens were included in this study during the period 2011─2016. The minimum inhibitory concentrations (MICs) were determined by broth microdilution method and MIC₅₀/MIC₉₀ values were derived from MIC distribution. M. intracellulare had generally low susceptible rates than M. avium for almost all tested antimicrobials except ethambutol and amikacin. The susceptible rate to clarithromycin was >94% of the MAC without significant differences between the two species. The MIC₅₀ values of ciprofloxacin, clarithromycin, linezolid, moxifloxacin, and rifampicin were higher in M. intracellulare than in M. avium, contrary to the results of ethambutol with a higher MIC₅₀ in M. avium. In general, M. intracellulare showed a higher resistance rate and higher MIC₅₀ values than M. avium. Differences between this study and previous reports suggest regional differences in drug susceptibility profile of MAC species.     

Moxifloxacin resistance and genotyping of Mycobacterium avium and Mycobacterium intracellulare isolates in Japan

BackgroundAlthough fluoroquinolones are considered as alternative therapies of pulmonary Mycobacterium avium complex (MAC) disease, the association between fluoroquinolone resistance and MAC genotypes in clinical isolates from individuals not previously treated for MAC infection is not fully clear.MethodsTotals of 154 M. avium isolates and 35 Mycobacterium intracellulare isolates were obtained from treatment-naïve patients with pulmonary MAC disease at the diagnosis of MAC infection at 8 hospitals in Japan. Their susceptibilities of moxifloxacin were determined by broth microdilution methods. Moxifloxacin-resistant isolates were examined for mutations of gyrA and gyrB. Variable numbers of tandem repeats (VNTR) assay was performed using 15 M. avium VNTR loci and 16 M. intracellulare VNTR loci.ResultsMoxifloxacin susceptibility was categorized as resistant and intermediate for 6.5% and 16.9%, respectively, of M. avium isolates and 8.6% and 17.1% of M. intracellulare isolates. Although the isolates of both species had amino acid substitutions of Thr 96 and Thr 522 at the sites corresponding to Ser 95 in the M. tuberculosis GyrA and Gly 520 in the M. tuberculosis GyrB, respectively, these substitutions were observed irrespective of susceptibility and did not confer resistance. The VNTR assays showed revealed three clusters among M. avium isolates and two clusters among M. intracellulare isolates. No significant differences in moxifloxacin resistance were observed among these clusters.ConclusionsAlthough resistance or intermediate resistance to moxifloxacin was observed in approximately one-fourth of M. avium and M. intracellulare isolates, this resistance was not associated with mutations in gyrA and gyrB or with VNTR genotypes.     

Sibling cases of Mycobacterium avium complex disease associated with hematological disease

A 22-year-old man who was admitted to our respiratory division complaining of fever and cough of 1 month's duration had been diagnosed with myelodysplastic syndrome 5 years earlier. On admission, radiological findings showed bilateral diffuse small nodular shadows. Although the results of an acid-fast bacilli examination of blood, sputum, and urine samples were all negative, we initiated antituberculous therapy for suspected miliary tuberculosis because the histological diagnosis from a bone marrow biopsy was epitheloid granuloma. The abnormalities on his chest radiographs improved, but his left cervical lymph nodes became swollen. The histological result of a lymph node biopsy revealed epitheloid granuloma with caseating necrosis. The DNA–DNA hybridization result of a resected lymph node culture indicated Mycobacterium avium. The final diagnosis was disseminated Mycobacterium avium complex (MAC) disease. Both leukocytopenia and thrombocytopenia had been noted in the patient's 19-year-old younger brother, who had been living in the same home 5 years earlier, and for whom a diagnosis of myelodysplastic syndrome was made from bone marrow aspiration on admission. An infiltration shadow with nodular shadows was noted in the right upper lung field on a chest radiograph. A bronchoscopic examination revealed pulmonary MAC disease. As for the route of infection, although we investigated restriction fragment length polymorphism (RFLP), a different pattern was found in the two brothers. We suspect that they were infected by different species of Mycobacterium avium in the same environment rather than by droplet infection from the younger brother to the older brother.     

Specific amplification of gene encoding N-terminal region of catalase–peroxidase protein (KatG-N) for diagnosis of disseminated MAC disease in HIV patients

Disseminated Mycobacterium avium-intracellulare complex (MAC) infection is considered as severe complication of advanced HIV/AIDS disease. Currently available various laboratory investigations have not only limited ability to discriminate between MAC infection and tuberculosis but are also laborious and time consuming. The aim of this study was, therefore, to design a molecular-based strategy for specific detection of MAC and its differentiation from Mycobacterium tuberculosis (M. tb) isolated from the blood specimens of HIV patients. A simple PCR was developed based on the amplification of 120-bp katG-N gene corresponding to the first 40 amino acids of N-terminal catalase–peroxidase (KatG) protein of Mycobacterium avium that shows only ~13% sequence homology by clustal W alignment to N-terminal region of M. tb KatG protein. This assay allowed the accurate and rapid detection of MAC bacteremia, distinguishing it from M. tb in a single PCR reaction without any need for sequencing or hybridization protocol to be performed thereafter. This study produced enough evidence that a significant proportion of Indian HIV patients have disseminated MAC bacteremia, suggesting the utility of M. avium katG-N gene PCR for early detection of MAC disease in HIV patients.     

Redevelopment after spontaneous sputum conversion in noncavitary nodular bronchiectatic Mycobacterium avium complex lung disease

BackgroundAlthough spontaneous sputum conversion can occur in noncavitary nodular bronchiectatic (NC-NB) Mycobacterium avium complex lung disease (MAC-LD), little is known about redevelopment after spontaneous conversion. We investigated the redevelopment phenomenon after spontaneous sputum conversion in patients with NC-NB MAC-LD.Material and methodsAmong patients diagnosed with NC-NB MAC-LD between 2000 and 2013, 140 patients who experienced spontaneous sputum conversion, and whose follow-up duration after conversion was ≥6 months, were enrolled at a tertiary referral center in South Korea. Their medical records were retrospectively reviewed.ResultsOf the 140 patients, 34 (24.3%) underwent redevelopment during the median follow-up period of 71.0 months (interquartile range [IQR], 58.8–87.5). Redevelopment occurred at a median interval of 25.0 months (IQR, 11.5–41.8) after spontaneous sputum conversion. The mean age of the 34 patients with redevelopment was 63.6 years, and 73.5% were women. No statistically significant differences in clinical characteristics were noted between the 34 patients with redevelopment and those with persistent conversion. Among the 34 patients with redevelopment, 6 received treatment at a median interval of 8 months (IQR, 1.5–16.8) after redevelopment. No significant differences in clinical characteristics were noted between the six treated and 28 untreated patients.ConclusionAt least approximately 24% of patients with spontaneous sputum conversion in NC-NB MAC-LD had redevelopment, and a portion of them required treatment. These findings suggest that long-term follow-up is necessary for patients with NC-NB MAC-LD, even those who experience spontaneous sputum conversion.     

Characteristics of patients with bronchoscopy-diagnosed pulmonary Mycobacterium avium complex infection

Background

We occasionally treat patients with clinically suspected pulmonary Mycobacterium avium complex (MAC) infection and negative MAC culture on bronchoscopy.

Effective treatment for clarithromycin-resistant Mycobacterium avium complex lung disease

Clinical management of macrolide-resistant Mycobacterium avium complex (MR-MAC) lung disease is difficult. To date, there only exist a limited number of reports on the treatment of clarithromycin-resistant MAC (CR-MAC) lung disease. This study aimed to evaluate prognostic factors and identify effective treatments in CR-MAC lung disease. We retrospectively collected clinical data of patients newly diagnosed with CR-MAC lung disease at the Kinki-Chuo Chest Medical Center between August 2010 and June 2018. Altogether, 37 patients with CR-MAC lung disease were enrolled. The median age was 69 years; 30, 22, and 21 patients received clarithromycin, ethambutol, and rifampicin, respectively, on their own or in drug combination. The observed sputum culture conversion rate was 29.7% (11/37 patients). In univariate analysis, ethambutol significantly increased the rate of sputum culture conversion (p = 0.027, odds ratio (OR) 10; 95% confidence interval (CI) 1.11–89.77). Multivariate analysis confirmed that ethambutol increased sputum culture conversion rate (p = 0.026; OR 21.8; 95% CI 1.45–329) while the existence of lung cavities decreased it (p = 0.04; OR 0.088; 95% CI 0.009–0.887). The combined use of ethambutol with other drugs may improve sputum culture conversion rate in CR-MAC lung disease.     

Tolerability,adverse events,and efficacy of treatment for Mycobacterium avium complex pulmonary disease in elderly patients

IntroductionAlthough the number of patients with Mycobacterium avium complex (MAC) pulmonary disease has been increasing among the elderly individuals due to population aging in Japan, few studies have reported treatment in elderly patients with MAC pulmonary disease. We conducted a retrospective cohort study to evaluate differences in the tolerability of, adverse events associated with and efficacy of treatment for MAC pulmonary disease in elderly and nonelderly patients.MethodsThe medical records of 96 newly diagnosed MAC pulmonary disease patients at Nagoya City University Hospital between April 2014 and March 2019 were reviewed.ResultsElderly patients ≥75 years old started multidrug treatment less frequently than nonelderly patients <75 years old (17 of 41 patients, 41.5% vs. 41 of 55 patients, 74.5%, P = 0.001). The treated elderly patients had more symptoms, more extensive radiological disease and a higher rate of positivity on sputum smear than the treated nonelderly patients. Eleven elderly patients and 19 nonelderly patients continued the initial multidrug regimen (64.7% vs. 46.3%, P = 0.26). Adverse events occurred in 6 elderly patients and 25 nonelderly patients (35.3% vs. 61.0%, P = 0.074). The rates of achievement of sputum conversion and radiological improvement after treatment for over 1 year were similar between the elderly and nonelderly patients (61.5% vs. 75.0%, P = 0.37; 76.9% vs. 78.1%, P = 1).ConclusionsThe tolerability, adverse events, and efficacy of treatment in elderly patients with MAC pulmonary disease were not noticeably different from those in nonelderly patients.     

Identification of nontuberculous mycobacterial infection by IS6110 and hsp65 gene analysis on lung tissues

The clinical, histologic, and radiographic presentations of nontuberculous mycobacterial (NTM) lung disease are usually indistinguishable from those of reactivated pulmonary tuberculosis (TB), so it remains a great challenge for the clinician to make treatment decisions for patients with old TB and a positive culture result for NTM. This study investigated whether the mycobacterial specific heat shock protein 65 (hsp65) and Mycobacterium tuberculosis (MTB)-specific IS6110 gene would present in pulmonary lesions of patients with NTM pulmonary infection. Formalin-fixed and paraffin-embedded (FFPE) tissue blocks of 24 patients with NTM infections treated at the hospital from 1998 to 2008 were included. Mycobacterial hsp65 gene was amplified in 20 of the 24 patients, and the species identified by sequencing was consistent with corresponding culture results in 12 of these patients. MTB-specific IS6110 gene was detected in 3 of the 7 patients who had old TB and a subsequent diagnosis of fibrocavitary NTM lung disease. Polymerase chain reaction (PCR) analysis of hsp65 gene also confirmed the presence of MTB genes in 2 of these 3 patients. Our results indicate that PCR amplification and sequencing of the mycobacterial hsp65 gene is a sensitive assay for identification of NTM species in FFPE materials. However, consistent results of PCR analysis, microbiology study, histologic manifestations, radiology, and clinical presentation are important for correct diagnosis of NTM pulmonary infection. The presence of MTB gene in patients with fibrocavitary NTM lung lesions poses a clinical dilemma for deciding concurrent treatment TB and NTM infection.     

Cases of severe Mycobacterium avium lung disease occurred in a married couple caused by identical strain

Bacteria of the Mycobacterium avium complex, which are environmental organisms found in soil and water, have been found to cause human lung diseases. Although infection is reported to occur in cohabiting patients, the incidence of infection from the single clone remains rarely documented. Herein, we report a case of M. avium lung disease caused by specimens with the same clone strains in a married couple. The wife, a 67-year-old female, had severe M. avium lung disease despite receiving multidrug chemotherapy for eleven years. The husband, a 68-year-old male, died of acute lung injury complicated by M. avium pleurisy. The result of the variable-number tandem-repeat analysis of isolates from serial sputum specimens of both patients indicated that the severe M. avium lung disease in a married couple was caused by the isolates with identical pattern. This case were considered to have acquired clarithromycin resistance during each clinical course, revealing the possibility of infection with a strain that may induce severe pulmonary condition.     

Nontuberculous mycobacterial infections in cancer patients in a medical center in Taiwan, 2005-2008

Data on the nontuberculous mycobacterial (NTM) species that cause infection and the characteristics of disease caused by these pathogens in cancer patients are limited, so we perform this study to investigate the species distribution of NTM isolates from various clinical specimens and to elucidate the epidemiologic trends in NTM isolates and diseases among cancer patients. From 2005 through 2008, cancer patients with NTM infections as defined by the American Thoracic Society/Infectious Diseases Society of America criteria were identified at the National Taiwan University Hospital. The medical records of all patients were reviewed. During the study period, a total of 219 cancer patients with NTM infections were identified. Among them, 133 (60.7%) patients were older than 65 years, most of whom were men. Lung cancer was the most common type of cancer, followed by hematologic cancer and gastrointestinal tract cancer. Pulmonary NTM infection was the most common type of infection in 205 (93.6%) patients, followed by skin and soft tissue infections (n = 7, 3.2%), disseminated infections (n = 4, 1.8%), and genitourinary tract infection (n = 3, 1.4%). Disseminated infections occurred exclusively in patients with hematologic cancer. Mycobacterium avium complex (MAC) caused the majority of pulmonary NTM infections in cancer patients; in contrast, M. abscessus was the most common causative pathogen of extrapulmonary NTM diseases, followed by MAC. In conclusion, physicians need to be aware of the possibility of co-existing pulmonary NTM infection in patients with lung cancer. In addition, disseminated NTM infection should be considered in patients with hematologic cancer.     

Evaluation of the MycoAKT Latex Agglutination Test for Rapid Diagnosis of Mycobacterium avium Complex Infections

Rapid diagnosis of Mycobacterium avium complex (MAC) bacteremia is important for management of patients with the acquired immunodeficiency syndrome who have disseminated MAC. The purpose of this study was to determine the reliability of the MycoAKT latex agglutination test for direct detection of MAC in positive mycobacterial blood cultures. First, colonies of isolates of previously identified mycobacteria, including 35 MAC, were tested. Of the 55 isolates evaluated, 33 were identified as MAC by the latex test, including 31 of the known MAC and 2 M. chelonae (sensitivity, 88.6%; specificity, 90.0%). Second, broth from 20 ESP II and 20 BACTEC 12B bottles seeded with isolates of MAC were tested. Aliquots from 19 (95%) ESP II cultures and 16 (80%) 12B cultures were positive by the latex test. In phase 3, broth from 115 signal-positive ESP II blood cultures were tested by latex agglutination. Forty-three subcultures from these bottles grew mycobacteria (41 MAC and 2 Mycobacterium tuberculosis complex); the remainder grew no organisms. Broth from 40 of the blood cultures (39 that grew MAC and 1 from which no organisms were recovered) were latex positive; thus, the sensitivity, specificity, and positive and negative predictive values of the latex test for direct identification of MAC in ESP II blood cultures were 95.1, 98.6, 97.5, and 97.3%, respectively. The mean time to detection of MAC was 14.6 days (range, 6–34 days) with the direct latex test, compared with 18.3 days (range, 9–36 days) with subculture and probe (p < 0.05).