Nontuberculous mycobacterial lung diseases

Pathogenicity and virulence of Mycobacterium abscessus

Non-tuberculous mycobacteria (NTM), such as Mycobacterium abscessus (Mab) are an increasing cause of human disease. While the majority of immunocompetent hosts control Mab infections, the robust survival of Mab within the environment has shaped survival in human cells to help drive persistence and cause inflammatory damage in susceptible individuals. With high intrinsic resistance to antibiotics, there is an important need to fully understand how Mab causes infection, define protective host pathways that control disease, and develop new strategies to treat those at high risk. This review will examine the existing literature related to host-Mab interactions with a focus on virulence, the host response, and therapy development. The goal is to highlight key gaps in our understanding and describe novel approaches to encourage new research avenues that better define the pathogenesis and host response against this increasingly important human pathogen.

Treatment for non-tuberculous mycobacteria: challenges and prospects

Non-Tuberculous mycobacteria (NTM) are opportunistic environmental bacteria. Globally, NTM incidence is increasing and modeling suggests that, without new interventions, numbers will continue to rise. Effective treatments for NTM infections remain suboptimal. Standard therapy for Mycobacterium avium complex, the most commonly isolated NTM, requires a 3-drug regime taken for approximately 18 months, with rates of culture conversion reported between 45 and 70%, and high rates of relapse or reinfection at up to 60%. New therapeutic options for NTM treatment are urgently required. A survey of ongoing clinical trials for new NTM therapy listed on ClinicalTrials.Gov using the terms 'Mycobacterium avium', 'Mycobacterium abscessus', 'Mycobacterium intracellulare', 'Non tuberculous Mycobacteria' and 'Nontuberculous Mycobacteria' and a selection criterion of interventional studies using antibiotics demonstrates that most trials involve dose and combination therapy of the guideline based therapy or including one or more of; Amikacin, Clofazimine, Azithromycin and the anti-TB drugs Bedaquiline and Linezolid. The propensity of NTMs to form biofilms, their unique cell wall and expression of both acquired and intrinsic resistance, are all hampering the development of new anti-NTM therapy. Increased investment in developing targeted treatments, specifically for NTM infections is urgently required.

Atypical mycobacterial infection masquerading as an endobronchial growth in an immunocompromised host

Non-tuberculous mycobacteria (NTM) are ubiquitous organisms. Endobronchial growth as a presenting feature of NTM disease is uncommon. Here we present a case of a patient with retroviral disease on antiretroviral therapy, presenting with cough, wheezing and exertional dyspnoea. High-resolution CT showed a partial obstruction of the left main bronchus (LMB). Bronchoscopy showed an endobronchial growth in the distal LMB. An endobronchial biopsy showed non-necrotising granulomas; bronchial wash for acid-fast bacilli was positive and culture grew Mycobacterium avium complex. He was treated with a combination therapy of clarithromycin, rifampicin and ethambutol. Repeat bronchoscopy after 6 weeks of therapy showed complete resolution of the endobronchial growth.

Risk Factors and Mental Health Status in Patients With Non-Tuberculous Mycobacterial Lung Disease: A Single Center Retrospective Study

According to the existing data, the incidence and prevalence of non-tuberculous mycobacteria (NTM) are increasing worldwide. The risk factors and mental health status of patients with NTM lung disease are important and deserve our attention. A total of 180 patients with NTM lung disease hospitalized from January 2018 to December 2021 were selected as the NTM group, and 90 patients with non-severe community-acquired pneumonia (CAP) who were hospitalized during the same period were selected as the control group. The Symptom Checklist-90 (SCL-90) was used to assess the mental health status of the patients. The data were analyzed using descriptive statistics, logistic regression, and receiver operating characteristic (ROC) curves. There were no significant differences in age, sex, marital status, or smoking history between the two groups (p > 0.05), but there were significant differences in educational level, underlying diseases, occupation, living environment, and body mass index (BMI) (p < 0.01). According to the classification of basic diseases, bronchiectasis was found in 82 (45.6%) patients, followed by hypertension in 66 (36.7%) patients, and chronic obstructive pulmonary disease (COPD) in 39 (21.7%) patients. The NTM strains were identified M. intercelleulare caused 41 cases (22.8%), followed by Mycobacterium avium and Mycobacterium gordonae, each with 35 cases (19.4%), and Mycobacterium abscessus with 32 cases (17.8%). The SCL-90 found that 160 (88.9%) of 180 patients with NTM lung disease had developed mental health problems, among which the four highest-scoring factors were anxiety (ANX: 29.4%), depression (DEPR: 18.8%), sleep and diet (SD: 16.9%), and somatization (SOM: 11.3%). Through multivariate logistic regression analysis, it was found that educational level, underlying diseases, living environment, and BMI were independent risk factors for the occurrence of NTM lung disease (p < 0.01). The Hosmer-Lemeshow test was used to check the model's fitness. The ROC curve showed that the area under the curve (AUC) was 0.896, the sensitivity was 83.3%, and the specificity was 85.6%. Patients with NTM lung disease have many risk factors and prominent mental health problems that may require interventions during the process of clinical diagnosis and treatment.

External quality assessment by European mycobacterial laboratories: results of AFB microscopy and identification rounds

We analyzed mycobacterial stain, culture and identification EQA data from altogether 134 laboratories in 15 mainly European countries over a 4-year period. The aim was to get an overview of the performance and methods and identify diagnostic challenges. The overall success rates for staining and identification were 94% and 91%. The false negative rate for staining was significantly higher for the medium positive than the strong positive slides (11% vs 4%). The false positive rate on negative slides was 10%, indicating contamination issues. The overall success of M. tuberculosis detection was high with error rates ranging from 0.7% to 1.2%. Pre- or postanalytical errors accounted for most of the unsuccessful responses. The detection of nontuberculous mycobacteria (NTM) was less consistent; accurate species identification depended on the assays used. Only 19% of participants performed species level identification for NTMs, 47% detected the presence NTMs while 21% focused on ruling out TB.

Non-tuberculous mycobacteria, not Mycobacterium bovis, are a significant cause of TB-like lesions observed in slaughtered cattle in Ghana

Objectives

The aim was to isolate and identify the species of mycobacteria causing tuberculous-like (TB-like) lesions in cattle in Ghana.

Methods

Between 2019 and 2020, 68 bovine tissue samples with TB-like lesions, identified during post slaughter examination, were obtained from four major abattoirs close to border towns in Ghana. The samples were cultured on Lowenstein-Jensen medium. Isolated bacteria were characterized by Ziehl-Neelsen staining and observation for acid-fast bacilli (AFB) under a microscope. DNA was extracted from AFB-positive isolates, and mycobacterial speciation was performed by line probe assay using GenoType Mycobacterium CM and also with mycobacterial 16S rRNA gene amplification and sequencing.

Results

No Mycobacterium bovis was identified; however 53 bacterial isolates were obtained, of which 41 were non-tuberculous mycobacteria (NTM) strains and 12 were gram-positive bacteria. The predominant NTM species was M. fortuitum (43.9%, 18/41), with the rest being M. novocastrense, M. terrae, M. flavescens, M. holsaticum, M. cosmeticum, M. virginiense, M. intracellulare, M. mageritense, M. minnesotensis, M. duvalii, M. lehmannii, and M. koreense.

Conclusions

In cattle, NTM contribute significantly to lesions observed during slaughter examination and may be an important cause of zoonotic tuberculosis. A One Health surveillance of NTM in Ghana would provide insights into their clinical significance.

The Rise of Non-Tuberculosis Mycobacterial Lung Disease

The incidence and number of deaths from non-tuberculous mycobacterial (NTM) disease have been steadily increasing globally. These lesser known “cousins” of Mycobacterium tuberculosis (TB) were once thought to be harmless environmental saprophytics and only dangerous to individuals with defective lung structure or the immunosuppressed. However, NTM are now commonly infecting seemingly immune competent children and adults at increasing rates through pulmonary infection. This is of concern as the pathology of NTM is difficult to treat. Indeed, NTM have become extremely antibiotic resistant, and now have been found to be internationally dispersed through person-to-person contact. The reasons behind this NTM increase are only beginning to be elucidated. Solutions to the problem are needed given NTM disease is more common in the tropics. Importantly, 40% of the world's population live in the tropics and due to climate change, the Tropics are expanding which will increase NTM infection regions. This review catalogs the global and economic disease burden, at risk populations, treatment options, host-bacterial interaction, immune dynamics, recent developments and research priorities for NTM disease.

Comparison of chest CT findings in nontuberculous mycobacterial diseases vs. Mycobacterium tuberculosis lung disease in HIV-negative patients with cavities

Objectives

This article focuses on the differences between CT findings of HIV-negative patients who have cavities with nontuberculous mycobacteria (NTM) disease and those with Mycobacterium tuberculosis infections (TB).

Methods

We retrospectively reviewed 128 NTM disease patients (79 males and 49 females) with cavities in chest CT, matched for age and gender with 128 TB patients in the same period. Sputum cultures of all patients were positive for pathogens. Two independent chest radiologists evaluated the characteristics of the largest cavity and related factors.

Results

Interobserver agreement was excellent (κ value, 0.853–0.938). Cavity walls in NTM disease were significantly thinner (6.9±4 mm vs 10.9±6 mm, P<0.001) and more even (the ratio of thickness, 2.6±1 vs 3.7±2, P<0.001) than those in TB. The thickening of adjacent pleura next to the cavity was also significantly thicker in NTM than TB (P<0.001). However, in the multivariate analysis, thickening of adjacent pleura was the only significant factor among the representative cavity findings (Odds ratio [OR], 6.49; P<0.001). In addition, ill-defined tree-in-bud nodules (OR, 8.82; P<0.001), number of non-cavitary nodules (≥10mm) (OR, 0.72; P = 0.003), and bronchiectasis in the RUL (OR, 5.3; P = 0.002) were significantly associated ancillary findings with NTM disease in the multivariate analysis.

Conclusions

The major cavities in NTM disease generally have thinner and more even walls than those in TB. When cavities are associated with adjacent pleural thickening, ill-defined satellite tree-in-bud nodules, or fewer non-cavitary nodules ≥10 mm, these CT findings are highly suggestive of NTM disease rather than TB.

Nontuberculous Mycobacteria Isolated from Tuberculosis Suspects in Ibadan, Nigeria

In Nigeria, one of the highest tuberculosis (TB) burdened nations, sputum smear microscopy is routinely employed for TB diagnosis at Directly Observed Treatment Short-Course (DOTS) Centers. This diagnostic algorithm does not differentiate Mycobacterium tuberculosis complex (MTC) from nontuberculous mycobacteria (NTM). Between December 2008 and January 2009, consecutive patients diagnosed with TB were screened for inclusion at 10 DOTS centers in Ibadan, Nigeria. To verify Mycobacterium species in patients diagnosed, we cultured and identified mycobacterial isolates using PCR, line probe assay, and spoligotyping techniques. From 48 patients screened, 23 met the inclusion criteria for the study. All the 23 study patients had a positive culture. Overall, we identified 11/23 patients (48%) with MTC only, 9/23 (39%) with NTM only, and 3/23 (13%) with evidence of both MTC and NTM. Strains of MTC identified were Latin American Mediterranean (LAM) genotype (n = 12), M. africanum (n = 1), and the genotype family T (n = 1). Four M. avium-intracellulare-M. scrofulaceum complexes, one M. chelonae complex, one M. abscessus, and one M. intracellulare were identified. Our findings underscore the need to incorporate molecular techniques for more precise diagnosis of TB at DOTS centers to improve clinical outcomes and safe guard public health, particularly in TB endemic countries.

Non-tuberculous mycobacteria (NTM) in Zambia: prevalence, clinical, radiological and microbiological characteristics

Background

Non-tuberculous mycobacteria (NTM) infection is an emerging health problem. We present here the Zambia-specific national level data of prevalence, symptomatic, radiological and microbiological characteristics of NTM, using results from a national Tuberculosis (TB) prevalence survey.

Methods

This was a cross-sectional study of the prevalence of NTM among adults aged 15 years and above, who were participants in a national TB prevalence survey. Participants who had either an abnormal chest x-ray or were symptomatic were considered presumptive TB cases and submitted sputum for smear and culture analysis. HIV testing was performed on an opt-out basis. Symptomatic NTM prevalence was estimated from individual level analysis.

Results

Of the 6,123 individuals with presumptive TB, 923 (15.1 %) were found to have NTM, 13 (0.2 %) were MTB/NTM co-infected and 338 (5.5 %) were contaminated (indeterminate). The prevalence of symptomatic NTM was found to be 1,477/100,000 [95 % CI 1010–1943]. Smear positivity, history of cough or chest pain and HIV positivity were risk factors for NTM.

Conclusion

This first study to estimate the national prevalence of NTM in Zambia indicates that the burden is high. The NTM occurrence in Zambia constitutes both a public health and ethical issue requiring action from health managers.

Clinical Significance of Environmental Mycobacteria Isolated From Respiratory Specimens of Patients With and Without Silicosis

OBJECTIVE

To describe the clinical, functional and radiographic differences of respiratory disease caused by environmental mycobacteria (EM) in patients with and without silicosis.

METHOD

Retrospective, observational study in patients with nontuberculous mycobacteria isolated in the Hospital Meixoeiro (University Hospital of Vigo) microbiology laboratory between January 2007 and December 2013. Patients were grouped according to the presence or absence of silicosis and mycobacterial lung disease, using American Thoracic Society criteria.

RESULTS

In 156 cases, at least one species of EM had been isolated from the respiratory culture. A total of 71% were identified in men, 40 (25.6%) of whom had silicosis. Sixty patients (38.5%) met American Thoracic Society microbiological criteria: 62.5% of the silicosis group and 30.2% of the non-silicosis group. The most common species were Mycobacterium avium complex, Mycobacterium genavense and Mycobacterium chelonae. American Thoracic Society criteria for environmental mycobacterial disease were met in 34 (22.7%) patients: 14 in the silicosis group and 20 in the non-silicosis group. Treatment was administered in 24 cases, with better bacteriological eradication levels in the non-silicosis group.

CONCLUSIONS

In our series, a history of silicosis was related with a higher incidence of environmental mycobacterial disease. The causative species in the majority of cases in our setting was Mycobacterium avium complex, followed by Mycobacterium genavense. Patients with silicosis showed lower cure rates after treatment.

Clinical findings in relation to mortality in non-tuberculous mycobacterial infections: patients with Mycobacterium avium complex have better survival than patients with other mycobacteria

We compared the clinical findings and survival in patients with Mycobacterium avium complex (MAC) and other non-tuberculous mycobacteria (NTM). A total of 167 adult non-human immunodeficiency virus (HIV) patients with at least one positive culture for NTM were included. Medical records were reviewed. The patients were categorised according to the 2007 American Thoracic Society (ATS) criteria. MAC comprised 59 % of all NTM findings. MAC patients were more often female (70 % vs. 34 %, p < 0.001) and had less fatal underlying diseases (23 % vs. 47 %, p = 0.001) as compared to other NTM patients. Symptoms compatible with NTM infection had lasted for less than a year in 34 % of MAC patients but in 54 % of other NTM patients (p = 0.037). Pulmonary MAC patients had a significantly lower risk of death compared to pulmonary other NTM (hazard ratio [HR] 0.50, 95 % confidence interval [CI] 0.33–0.77, p = 0.002) or subgroup of other slowly growing NTM (HR 0.55, 95 % CI 0.31–0.99, p = 0.048) or as rapidly growing NTM (HR 0.47, 95 % CI 0.25–0.87, p = 0.02). The median survival time was 13.0 years (95 % CI 5.9–20.1) for pulmonary MAC but 4.6 years (95 % CI 3.4–5.9) for pulmonary other NTM. Serious underlying diseases (HR 3.21, 95 % CI 2.05–5.01, p < 0.001) and age (HR 1.07, 95 % CI 1.04–1.09, p < 0.001) were the significant predictors of mortality and female sex was a predictor of survival (HR 0.38, 95 % CI 0.24–0.59, p < 0.001) in the multivariate analysis. Pulmonary MAC patients had better prognosis than pulmonary other NTM patients. The symptom onset suggests a fairly rapid disease course.

A case of erosive polyarthritis in a patient diagnosed with a suspicion of atypical mycobacteria

In this report, we introduce a case of erosive polyarthritis in a 55-year-old female diagnosed with Mycobacterium abscessus pulmonary infection. Her arthritis has been worsened after use of DMARDs. The patient demonstrated a significant response to the antimicrobial regimen that was administered. We call special attention to the possibility of Mycobacterium abscessus being a cause of reactive polyarthritis, particularly if symptoms worsened after use of disease-modifying antirheumatic drugs (DMARDs), but further studies are necessary for clarification.

Abnormal nasal nitric oxide production, ciliary beat frequency, and Toll-like receptor response in pulmonary nontuberculous mycobacterial disease epithelium

RATIONALE

Pulmonary nontuberculous mycobacterial (PNTM) disease has increased over the past several decades, especially in older women. Despite extensive investigation, no consistent immunological abnormalities have been found. Using evidence from diseases such as cystic fibrosis and primary ciliary dyskinesia, in which mucociliary dysfunction predisposes subjects to high rates of nontuberculous mycobacterial disease that increase with age, we investigated correlates of mucociliary function in subjects with PNTM infections and healthy control subjects.

OBJECTIVES

To define ex vivo characteristics of PNTM disease.

METHODS

From 2009 to 2012, 58 subjects with PNTM infections and 40 control subjects were recruited. Nasal nitric oxide (nNO) was determined at the time of respiratory epithelial collection. Ciliary beat frequency at rest and in response to Toll-like receptor (TLR) and other agonists was determined using high-speed video microscopy.

MEASUREMENTS AND MAIN RESULTS

We found decreased nNO production, abnormally low resting ciliary beat frequency, and abnormal responses to agonists of TLR2, -3, -5, -7/8, and -9 in subjects with PNTM compared with healthy control subjects. The low ciliary beat frequency in subjects with PNTM was normalized ex vivo by augmentation of the NO-cyclic guanosine monophosphate pathway without normalization of their TLR agonist responses.

CONCLUSIONS

Impaired nNO, ciliary beat frequency, and TLR responses in PNTM disease epithelium identify possible underlying susceptibility mechanisms as well as possible avenues for directed investigation and therapy.

Mycobacterial infections in patients treated with tumor necrosis factor antagonists in South Korea

BACKGROUND

The aims of this study were to determine the incidence of tuberculosis (TB) and nontuberculous mycobacteria (NTM) lung disease in patients who were treated with tumor necrosis factor (TNF) antagonists in South Korea and to evaluate their clinical characteristics.

METHODS

We surveyed all patients (N = 509) who were treated with TNF antagonists at Severance Hospital, South Korea, between January 2002 and December 2011. We reviewed the patients' medical records and collected microbiological, radiographic, and clinical data, including the type of TNF blocker(s) used and the results of tuberculin skin tests and interferon-gamma release assays.

RESULTS

Rheumatoid arthritis (43.6 %) and ankylosing spondylitis (27.9 %) were the most common diseases in the patients treated with TNF antagonists. Patients received etanercept (33.4 %), infliximab (23.4 %), or adalimumab (13.2 %). The remaining patients received two or more TNF antagonists (30 %). Nine patients developed TB, and four patients developed NTM lung disease. After adjustment for age and sex, the standardized TB incidence ratio was 6.4 [95 % CI 3.1-11.7] compared with the general population. The estimated NTM incidence rate was 230.7 per 100,000 patients per year.

CONCLUSIONS

Our results show that mycobacterial infections increase in patients treated with TNF antagonists. The identification of additional predictors of TB for the treatment of latent tuberculosis infection and the careful monitoring and timely diagnosis of NTM-related lung disease are needed for patients who receive long-term therapy with TNF antagonists.

Non-tuberculous mycobacterial pulmonary infection in the immunocompetent host

Throughout much of the world, the incidence of non-tuberculous mycobacterial pulmonary infections in immunocompetent hosts is on the rise. These organisms are widespread in the natural environment; the explanation for what appears to be an increased susceptibility among human hosts is uncertain. Among more than 120 known species, the most common pathogenic isolate in the USA is Mycobacterium avium complex. The diagnosis of pulmonary disease caused by M. avium complex requires a compatible history, suggestive radiographic findings (on chest computed tomography) and microbiologic confirmation on culture of respiratory samples (sputum or direct lung sampling). Treatment options have improved with inclusion of macrolide antibiotics in a multi-drug regimen, but failure rates remain high (20-40%) even after a prolonged course of therapy. Newer, less toxic and more effective anti-mycobacterial agents are greatly needed for treatment of this increasingly common respiratory disease.

Prognostic value of American Thoracic Society criteria for non-tuberculous mycobacterial disease: a retrospective analysis of 120 cases with four years of follow-up

BACKGROUND

Non-tuberculous mycobacteria (NTM) cause disease in healthy and immunocompromised patients. The American Thoracic Society (ATS) 2007 diagnostic criteria were devised to distinguish NTM disease from airway colonization. The aim of this study was to evaluate the prognostic value of the ATS criteria.

METHODS

In a 4-y follow-up study that ended on 8 June 2006, we retrospectively analyzed the symptoms, underlying diseases, and mortality of 120 adult non-HIV patients with NTM culture findings obtained between 1990 and 1998. We categorized the patients according to the 2007 ATS NTM case definition into positive and negative groups.

RESULTS

Only 61/120 patients (51%) fulfilled the ATS criteria for NTM disease. As compared to ATS-negative subjects, the ATS-positive group showed lower age, a higher proportion of females, and fewer fatal underlying diseases. Among ATS-negative subjects, 46/59 (78%) did not fulfil the microbiological criteria and 43/59 (73%) did not fulfil the radiological criteria. Mycobacterium avium complex (MAC) comprised 61% of isolations in the ATS-positive and 47% in the ATS-negative group (p = 0.15). No significant difference in median survival time was found between the groups: ATS-positive 7.4 y (95% confidence interval (CI) 0.2-14.6) and ATS-negative 5.3 y (95% CI 3.0-7.6). No significant difference was found in symptoms except fatigue, which was more common in the ATS-positive (56% vs 37%, p = 0.04). Symptoms lasted for less than a year in 48%, which suggests a more rapid disease progression than has previously been reported.

CONCLUSIONS

The fulfillment of ATS criteria was poorly associated with any difference in prognosis, and based on our findings would be a poor prognostic marker.

Radiological features and therapeutic responses of pulmonary nontuberculous mycobacterial disease in rheumatoid arthritis patients receiving biological agents: a retrospective multicenter study in Japan

Objective

This study was performed to evaluate the radiological features of and therapeutic responses to pulmonary disease caused by nontuberculous mycobacteria (NTM) in the setting of biological therapy for rheumatoid arthritis (RA).

Methods

We conducted a retrospective chart review of 13 patients from multiple centers who had developed pulmonary NTM disease during biological therapy for RA, including infliximab, etanercept, adalimumab, and tocilizumab.

Results

Most cases were asymptomatic or resulted in only common-cold-like symptoms. Abnormalities in computed tomography (CT) imaging were protean and frequently overlapped. The most predominant pattern was nodular/bronchiectatic disease (six cases), followed by alveolar infiltrate (three cases), cavitary disease (two cases), and pulmonary nodules (two cases). In most cases, pulmonary NTM disease had spread from a preexisting lesion; in particular, bronchial/bronchiolar abnormalities. In three cases, one or more nodular lesions with or without calcification were a focus of disease. Following the discontinuation of biological agents, most patients responded to anti-NTM therapy. Two patients showed no exacerbation in the absence of any anti-NTM therapy. In one patient, restarting tocilizumab therapy while continuing to receive adequate anti-NTM therapy produced a favorable outcome. In two other patients with a previous history of pulmonary NTM disease, introducing biological therapy led to recurrence, but anti-NTM therapy was effective in these patients.

Conclusion

CT abnormalities of pulmonary NTM disease in RA patients receiving biological therapy were variable, but were not unique to this clinical setting. NTM disease can spread from preexisting structural abnormalities, even if they are minute. Contrary to our expectations, the therapeutic outcomes of pulmonary NTM disease were favorable in these patients.

IL-32 expression in the airway epithelial cells of patients with Mycobacterium avium complex lung disease

Lung disease due to Mycobacterium avium complex (MAC) organisms is increasing. A greater understanding of the host immune response to MAC organisms will provide a foundation to develop novel therapies for these recalcitrant infections. IL-32 is a newly described pro-inflammatory cytokine that enhances host immunity against various microbial pathogens. Cytokines that induce IL-32 such as interferon-gamma, IL-18, IL-12 and tumor necrosis factor-alpha are of considerable importance to mycobacterial immunity. We performed immunohistochemistry and morphometric analysis to quantify IL-32 expression in the lungs of 11 patients with MAC lung disease and 10 controls with normal lung tissues. After normalizing for basement membrane length, there was a profound increase in IL-32 expression in the airway epithelial cells of the MAC-infected lungs compared with controls. Following normalization for alveolar surface area, there was a trend toward increased IL-32 expression in type II alveolar cells and alveolar macrophages in the lungs of MAC patients. Human airway epithelial cells (BEAS-2B) infected with M. avium produced IL-32 by a nuclear factor-kappa B-dependent mechanism. In both BEAS-2B cells and human monocyte-derived macrophages, exogenous IL-32γ significantly reduced the growth of intracellular M. avium. This finding was corroborated by an increase in the number of intracellular M. avium recovered from THP-1 monocytes silenced for endogenous IL-32 expression. The anti-mycobacterial effect of IL-32 may be due, in part, to increased apoptosis of infected cells. These findings indicate that IL-32 facilitates host defense against MAC organisms but may also contribute to the airway inflammation associated with MAC pulmonary disease.

Mycobacterial infections in adult patients with hematological malignancy

We retrospectively analyzed the clinical and microbiological characteristics of adult patients with hematological malignancy and nontuberculous mycobacteria (NTM) infections from 2001 to 2010. During the study period, 50 patients with hematological malignancy and tuberculosis (TB) were also evaluated. Among 2,846 patients with hematological malignancy, 34 (1.2%) patients had NTM infections. Mycobacterium avium-intracellulare complex (13 patients, 38%) was the most commonly isolated species, followed by M. abscessus (21%), M. fortuitum (18%), and M. kansasii (18%). Twenty-six patients had pulmonary NTM infection and eight patients had disseminated disease. Neutropenia was more frequently encountered among patients with disseminated NTM disease (p = 0.007) at diagnosis than among patients with pulmonary disease only. Twenty-five (74%) patients received adequate initial antibiotic treatment. Five of the 34 patients died within 30 days after diagnosis. Cox regression multivariate analysis showed that chronic kidney disease (p = 0.017) and neutropenia at diagnosis (p = 0.032) were independent prognostic factors of NTM infection in patients with hematological malignancy. Patients with NTM infection had higher absolute neutrophil counts at diagnosis (p = 0.003) and a higher 30-day mortality rate (15% vs. 2%, p = 0.025) than TB patients. Hematological patients with chronic kidney disease and febrile neutropenia who developed NTM infection had significant worse prognosis than patients with TB infection.

Role of histology in the diagnosis of infectious causes of granulomatous lung disease

PURPOSE OF REVIEW

Histologic examination and microbiologic cultures are the gold standards for the diagnosis of infectious granulomatous lung diseases. Although biopsies require invasive procedures, they often yield information that cannot be obtained by other methods. The aims of this article are to outline the major infections that cause granulomatous inflammation in the lung and to familiarize clinicians with the utility of histologic examination in their diagnosis.

RECENT FINDINGS

The histopathologic features of acute pulmonary histoplasmosis and granulomatous Pneumocystis pneumonia have been described in detail, the relative contributions of histology and microbiologic cultures in the diagnosis of blastomycosis have been delineated, and Cryptococcus gattii has emerged as a significant cause of granulomatous pulmonary nodules.

SUMMARY

The major infectious causes of granulomatous lung disease are mycobacteria and fungi. Histologic examination is particularly important in the diagnosis of pulmonary granulomatous infections when clinical, radiologic and serologic findings are nonspecific. Histology and microbiology play complementary but distinct roles in diagnosis. For organisms that grow slowly in cultures, histology has the additional advantage of being able to provide a rapid diagnosis.