An official ATS/IDSA statement: diagnosis, treatment, and prevention of nontuberculous mycobacterial diseases

Spinal infection caused by Mycobacterium avium complex in a patient with no acquired immune deficiency syndrome: a case report

Spinal infection caused by Mycobacterium avium complex (MAC) is rarely seen in people who do not have acquired immune deficiency syndrome. We report such a case in a 60-year-old man who underwent anterior spinal fusion after treatment with antibiotics had failed. The presentation of MAC spinal infection is different from that seen in MAC lung infection, with more than half presenting with urgent or semi-urgent neurological deficits. Younger patients who are not immunocompromised can also be infected. It should be considered as a differential diagnosis in patients with tuberculosis of the spine. The use of antibiotics should be based on the cultured organism's sensitivity results. Indications for surgery are progressive bony destruction, abscess formation, and neurological compression.

Guidelines on the diagnosis and treatment of pulmonary non-tuberculous mycobacteria infection

While the prevalence of Mycobacterium tuberculosis continues to decline in the developed world, the same cannot be said for non-tuberculous mycobacteria (NTM). These organisms are increasing in incidence and prevalence throughout the world. This is probably because of a combination of increased exposure, improved diagnostic methods and an increase in the prevalence of risk factors that predispose individuals to infection. Considerable confusion can arise in determining in the wide range of species whether an isolated NTM is in fact a contaminant or a pathogenic organism when isolated in sputum or bronchoalveolar lavage. This confusion combined with increasing requests for advice on the treatment of disease has led to the development of guidelines to assist the clinician in diagnosing and treating infection accurately.

Acute respiratory failure involving an R variant of Mycobacterium abscessus

We report the case of a cystic fibrosis patient colonized with a smooth-morphotype form of Mycobacterium abscessus who developed acute respiratory failure with the emergence of an isogenic rough (R) variant while he was recovering from peritonitis-induced shock. This report emphasizes the role of R forms in severe M. abscessus infections.

Virulence of Mycobacterium avium complex strains isolated from immunocompetent patients

Mycobacterium avium complex (MAC) disease has been increasing worldwide not only in immunocompromised but also in immunocompetent humans. However, the relationship between mycobacterial strain virulence and disease progression in immunocompetent humans is unclear. In this study, we isolated 6 strains from patients with pulmonary MAC disease. To explore the virulence, we examined the growth in human THP-1 macrophages and pathogenicity in C57BL/6 mice. We found that one strain, designated 198, which was isolated from a patient showing the most progressive disease, persisted in THP-1 cells. In addition, strain 198 grew to a high bacterial load with strong inflammation in mouse lungs and spleens 16 weeks after infection. To our knowledge, strain 198 is the first isolated MAC strain that exhibits hypervirulence consistently for the human patient, human macrophages in vitro, and even for immunocompetent mice. Other strains showed limited survival and weak virulence both in macrophages and in mice, uncorrelated to disease progression in human patients. We demonstrated that there is a hypervirulent clinical MAC strain whose experimental virulence corresponds to the serious disease progression in the patients. The existence of such strain suggests the involvement of bacterial virulence in the pathogenesis of pulmonary MAC disease in immunocompetent status.

Isolamento de micobactérias não-tuberculosas em São José do Rio Preto entre 1996 e 2005

OBJETIVO: Estudar a ocorrência de micobactérias não-tuberculosas e a variabilidade das espécies isoladas na região atendida pelo Instituto Adolfo Lutz-Regional de São José do Rio Preto-no período entre 1996 e 2005, assim como mostrar a importância do diagnóstico laboratorial. MÉTODOS: A partir de amostras pulmonares e extrapulmonares, foi realizado o isolamento de micobactérias, e estas foram identificadas por métodos fenotípicos e pelo método molecular polymerase chain reaction-restriction enzyme analysis. RESULTADOS: Foram isoladas 317 cepas de micobactérias não-tuberculosas: complexo Mycobacterium avium, 182 (57,4%); M. gordonae, 33 (10,4%); M. fortuitum, 25(7,9%); M. chelonae, 8 (2,5%); complexo M. terrae, 8 (2,5%); M. kansasii, 7 (2,2%); e espécies menos freqüentes, 54 (17%). No período, foram caracterizados 72 casos (33,3%) de micobacterioses, de acordo com os critérios bacteriológicos estabelecidos pela American Thoracic Society (2007).Desses, complexo M. avium foi responsável por 56 casos, sendo que 29 (51,8%) foram caracterizados como doença disseminada. M. fortuitum foi responsável por 6 casos; M. gordonae, 3; M. chelonae, 2; M. abscessus, 1; M. kansasii, 1; M. intracellulare, 1; M. malmoense, 1; e Mycobacterium ssp., 1. CONCLUSÕES: Os resultados obtidos mostraram a importância do diagnóstico bacteriológico das micobacterioses, pois a identificação das espécies possibilita a introdução de um tratamento adequado precocemente.

Multicenter cross-sectional study of nontuberculous mycobacterial infections among cystic fibrosis patients, Israel

This 2-year cross-sectional evaluation of nontuberculous mycobacterial (NTM) infections involved all Israeli medical centers that treat cystic fibrosis patients. The study comprised 186 patients whose sputum was analyzed for NTM. The prevalence of NTM isolates was 22.6%, and 6.5% and 10.8% of the patients fulfilled the 1997 and 2007 American Thoracic Society criteria for NTM lung disease, respectively. Mycobacterium simiae (40.5%), M. abscessus (31.0%), and M. avium complex (14.3%) were the most prevalent. Presence of Aspergillus spp. in sputum and the number of sputum specimens processed for mycobacteria were the most significant predictors for isolation of NTM (odds ratio [OR] = 5.14, 95% confidence interval [CI] 1.87-14.11 and OR = 1.47, 95% CI 1.17-1.85, respectively). The incidence of NTM pulmonary infections is increasing among cystic fibrosis patients, reflecting the increase in longevity of such patients as well as environmental exposure to various species of mycobacteria.

Mycobacterium chelonae necrotizing pneumonia after allogeneic hematopoietic stem cell transplant: report of clinical response to treatment with tigecycline

We present a case of progressive Mycobacterium chelonae ssp. chelonae necrotizing pneumonia after hematopoietic stem cell transplantation (HSCT) in the presence of chronic graft-versus-host disease. The patient failed to respond to standard combination therapy with multiple agents and developed resistance to most drugs over the course of treatment. Tigecycline, a new glycylcycline antimicrobial agent with in vitro activity against M. chelonae, was then used with a clinical response to treatment. To our knowledge, this is the first reported case demonstrating tigecycline to have a degree of clinical effectiveness to treat refractory pulmonary infection with M. chelonae in an HSCT recipient.

An unusual case of a cervical mass due to nontuberculous mycobacterium fortuitum infection

Mycobacterium fortuitum, of the class of nontuberculous mycobacteria, rarely causes cervical lymphadenopathy and head and neck masses. However, we treated a woman with a neck mass that was indeed caused by a mycobacterial infection. Our case is unique in that prompt recognition of the infection and treatment with antimicrobials averted surgery. Generally, both antibiotics and surgery are recommended, and in rare instances, infections can resolve with antibiotics alone. Nontuberculous M fortuitum infection should be included in the differential diagnosis of cervical masses, particularly in immunocompromised patients or those for whom standard antibiotics are not effective for treating abscess or lymphadenitis.

Clinical and immunologic features of an atypical intracranial mycobacterium avium complex (MAC) infection compared with those of pulmonary MAC infections

Members of the Mycobacterium avium complex (MAC) may cause chronic pulmonary infections in otherwise healthy elderly persons but rarely invade parts of the body outside of the lungs in immunocompetent hosts. We present a case of an isolated intracranial MAC infection in an apparently immunocompetent individual and review previous reports. We studied the T-cell and monocyte responses in healthy volunteers, individuals with a pulmonary MAC infection, and one individual with an isolated intracranial MAC infection. Genomic DNA from the individual with the brain MAC infection was studied for gamma interferon (IFN-gamma) receptor mutations. Individuals with localized pulmonary MAC infections showed increased activation of monocytes and enhanced monocyte and T-cell tumor necrosis factor alpha (TNF-alpha) production in response to lipopolysaccharide and MAC antigens but defects in T-cell IFN-gamma secretion. The individual with an intracranial MAC infection showed a lack of monocyte activation and deficiencies in both monocyte and T-cell TNF-alpha production and monocyte interleukin-12 (IL-12) production but had preserved T-cell IFN-gamma production. Mutations or deletions in the IFN-gamma receptor were not detected in the individual with the intracranial MAC infection. Our data suggest that distinct immune defects characterize two different manifestations of MAC infection. A relative defect in IFN-gamma production in response to MAC may predispose an individual to localized but partially controlled lung disease, whereas defects leading to reduced IL-12 and TNF-alpha production may allow the dissemination of MAC. Further studies delineating the potential role of TNF-alpha in limiting the spread of MAC outside the lung are warranted.

Late-onset posttraumatic skin and soft-tissue infections caused by rapid-growing mycobacteria in tsunami survivors

BACKGROUND

In the tsunami catastrophe in Thailand in 2004, several thousand Swedish tourists were injured, with contaminated crush trauma of the legs being the main cause of injury among the survivors.

METHODS

Patient and laboratory data for those who received hospital care in Stockholm and Gothenburg and contracted late-onset infections due to rapid-growing mycobacteria were reviewed retrospectively. Also, concomitant infections were recorded.

RESULTS

Fifteen patients with late-onset skin and soft-tissue infections due to rapid-growing mycobacteria are described here. Mycobacterium abscessus was isolated in 7 cases, Mycobacterium fortuitum was isolated in 6 cases, and Mycobacterium peregrinum and Mycobacterium mageritense were isolated in 1 case each. The infections appeared after a delay of 20-105 days (median, 60 days) after the trauma, targeting undamaged skin located near primary sutured wounds or skin grafts. Antimycobacterial drugs were given to 9 (60%) of the patients. The course of infection was protracted, but all infections due to rapid-growing mycobacteria healed within 12 months. Concomitant subcutaneous infections due to other microorganisms, such as Burkholderia pseudomallei or Cladophialophora bantiana, appeared early or late after the trauma.

CONCLUSIONS

Repeated cultures of abscess and wound specimens for Mycobacterium species may be needed to find the etiologic agents causing contaminated skin and soft-tissue infections, such as those that developed after traumas that occurred during the tsunami. These cultures are especially necessary when symptoms appear late and when conventional bacterial culture results are negative. A biopsy is recommended for the best yield and for complementary histopathological examination.

An association between Mycobacterium malmoense and coal workers' pneumoconiosis

An association between Mycobacterium malmoense and underlying lung disease has been described. The purpose of this study was to further explore this relationship and in particular to identify any relationship between Coal Workers' Pneumoconiosis (CWP) and M. malmoense infection. Patient charts were reviewed of all patients who had a positive sputum or bronchoalveolar lavage for M. malmoense from 1999 to 2006 in a large district general hospital in South Yorkshire, UK. We also performed a literature review in search of this association; one case report was found. Four patients had positive sputum cultures for M. malmoense but only three of these fulfilled the ATS 1997 criteria for diagnosis of disease. Of these three patients, all had clinical and radiologic evidence of CWP. This study strengthens the evidence of a link between nontuberculous mycobacteria and underlying lung disease but more importantly highlights an association between M. malmoense and CWP which has been rarely reported and is poorly understood.

Nontuberculous mycobacterial infections

CONTEXT

Nontuberculous mycobacteria include numerous acid-fast bacilli species, many of which have only recently been recognized as pathogenic. The diagnosis of mycobacterial disease is based on a combination of clinical features, microbiologic data, radiographic findings, and histopathologic studies.

OBJECTIVE

To provide an overview of the clinical and pathologic aspects of nontuberculous mycobacteria infection, including diagnostic laboratory methods, classification, epidemiology, clinical presentation, and treatment.

DATA SOURCES

Review of the pertinent literature and published methodologies.

CONCLUSIONS

Nontuberculous mycobacteria include numerous acid-fast bacilli species, many of which are potentially pathogenic, and are classified according to the Runyon system based on growth rates and pigment production. Their slow growth hinders cultures, which require special medium and prolonged incubation. Although such methods are still used, newer nucleic acid-based technologies (polymerase chain reaction and hybridization assays) can rapidly detect and speciate some mycobacteria--most notably, distinguishing Mycobacterium tuberculosis from other species. Infections caused by these organisms can present as a variety of clinical syndromes, not only in immunocompromised patients but also in immunocompetent hosts. Most common among these are chronic pulmonary infections, superficial lymphadenitis, soft tissue and osteoarticular infections, and disseminated disease. Treatment of nontuberculous mycobacterial infections is difficult, requiring extended courses of multidrug therapy with or without adjunctive surgical intervention.

Pulmonary nontuberculous mycobacterial disease: prospective study of a distinct preexisting syndrome

RATIONALE

Pulmonary nontuberculous mycobacterial (PNTM) disease is increasing, but predisposing features have been elusive.

OBJECTIVES

To prospectively determine the morphotype, immunophenotype, and cystic fibrosis transmembrane conductance regulator genotype in a large cohort with PNTM.

METHODS

We prospectively enrolled 63 patients with PNTM infection, each of whom had computerized tomography, echocardiogram, pulmonary function, and flow cytometry of peripheral blood. In vitro cytokine production in response to mitogen, LPS, and cytokines was performed. Anthropometric measurements were compared with National Health and Nutrition Examination Survey (NHANES) age- and ethnicity-matched female control subjects extracted from the NHANES 2001-2002 dataset.

MEASUREMENTS AND MAIN RESULTS

Patients were 59.9 (+/-9.8 yr [SD]) old, and 5.4 (+/-7.9 yr) from diagnosis to enrollment. Patients were 95% female, 91% white, and 68% lifetime nonsmokers. A total of 46 were infected with Mycobacterium avium complex, M. xenopi, or M. kansasii; 17 were infected with rapidly growing mycobacteria. Female patients were significantly taller (164.7 vs. 161.0 cm; P < 0.001) and thinner (body mass index, 21.1 vs. 28.2; P < 0.001) than matched NHANES control subjects, and thinner (body mass index, 21.1 vs. 26.8; P = 0.002) than patients with disseminated nontuberculous mycobacterial infection. A total of 51% of patients had scoliosis, 11% pectus excavatum, and 9% mitral valve prolapse, all significantly more than reference populations. Stimulated cytokine production was similar to that of healthy control subjects, including the IFN-gamma/IL-12 pathway. CD4(+), CD8(+), B, and natural killer cell numbers were normal. A total of 36% of patients had mutations in the cystic fibrosis transmembrane conductance regulator gene.

CONCLUSIONS

Patients with PNTM infection are taller and leaner than control subjects, with high rates of scoliosis, pectus excavatum, mitral valve prolapse, and cystic fibrosis transmembrane conductance regulator mutations, but without recognized immune defects.

Nontuberculous mycobacterial pulmonary disease

PURPOSE OF REVIEW

Pulmonary disease caused by nontuberculous mycobacteria is occurring with greater frequency, and previously unrecognized manifestations of nontuberculous mycobacteria are being identified. Paralleling this increase, improvements in laboratory techniques now allow for more precise identification of nontuberculous mycobacteria and recognition of new species. Consequently, clinicians are more often confronted with diagnostic and therapeutic challenges relevant to the care of patients with nontuberculous mycobacterial lung disease.

RECENT FINDINGS

In response to this burgeoning clinical need, the American Thoracic Society and Infectious Disease Society of America jointly published an updated consensus statement on nontuberculous mycobacterial pulmonary disease in 2007. This document, in conjunction with original investigations in the field, has advanced our understanding of the pathogenesis of nontuberculous mycobacterial lung disease, its clinical manifestations, and the efficacy of medical and surgical therapy.

SUMMARY

The present article will review our current understanding of nontuberculous mycobacterial pulmonary disease with particular emphasis on pathogenesis, diagnosis, and therapeutic decision making. Areas of clinical controversy in which current data are inadequate to guide our decision making will be highlighted.

Mycobacterial and other serious infections in patients receiving anti-tumor necrosis factor and other newly approved biologic therapies: case finding through the Emerging Infections Network

We present the results of a nationwide survey of infectious disease consultants to identify mycobacterial and other serious infections in patients receiving anti-tumor necrosis factor compounds and other novel targeted therapies. Nontuberculous mycobacterial infections, histoplasmosis, and invasive Staphylococcus aureus infection were all reported more frequently than was tuberculosis disease in this context.

Association between microsatellite polymorphisms in intron II of the human Toll-like receptor 2 gene and nontuberculous mycobacterial lung disease in a Korean population

This study evaluated the association between the guanine-thymine (GT) repeat polymorphism in intron II of the Toll-like receptor 2 (TLR2) gene and lung disease caused by nontuberculous mycobacteria (NTM). Polymerase chain reaction and gene scans were used to determine the numbers of GT repeats for 193 patients with the nodular bronchiectatic form of NTM lung disease, including 110 patients with Mycobacterium avium-intracellulare (MAC) infection, 82 patients with Mycobacterium abscessus infection, and 1 patient with co-infection of both organisms. These values were compared with the results for 191 controls. Genotypes with shorter GT repeats were more common among patients with NTM lung disease (50.8 vs 37.7%, p=0.01). In the subgroup analysis, genotypes that included S alleles were more common in the patients with MAC lung disease (53.6%, p=0.01, OR, 1.91; 95% CI, 1.16, 3.16) than in healthy controls, whereas this difference was not statistically significant in patients with M. abscessus lung disease (47.6%, p=0.13). In conclusion, these results suggest that the GT repeat microsatellite polymorphisms in intron II of the human TLR2 gene contribute to the development of NTM lung disease, especially MAC lung disease, in a Korean population.

Rapid speciation of 15 clinically relevant mycobacteria with simultaneous detection of resistance to rifampin, isoniazid, and streptomycin in Mycobacterium tuberculosis complex

OBJECTIVE

To design and standardize an in-house reverse line blot hybridization (RLBH) assay for the accurate identification of 15 clinically relevant species of mycobacteria and for the detection of drug resistance to rifampin (RIF), isoniazid (INH), and streptomycin (STR) in Mycobacterium tuberculosis complex (MTB).

MATERIAL AND METHODS

Oligonucleotides specific for 15 different species of mycobacteria and wild type and mutant alleles of selected codons in the rpobeta, inhA, katG, rpsL, and rrs genes were designed and immobilized on a membrane. A multiplex PCR was standardized to amplify all target genes. The assay was optimized using ATCC and known mutant strains. Three hundred MTB isolates, 85 non-tuberculous mycobacteria (NTM) isolates, and 48 smear-positive specimens were analyzed. Results were confirmed by PCR restriction enzyme assay and sequencing.

RESULTS

Upon RLBH analysis, among the NTM, 14% were identified as Mycobacterium fortuitum, 16% were identified as Mycobacterium abscessus, 20% showed 99% homology with Mycobacterium intracellulare, and 31% showed 98% homology with Mycobacterium simiae. Of the 300 MTB isolates analyzed, 75% RIF-resistant isolates had Ser531Leu mutation in the rpobeta gene. Of the INH-resistant isolates, 89% showed Ser315Thr mutation in the katG gene, whereas 16% showed -15 C-->T mutation in the promoter region of the inhA gene. Among STR-resistant isolates, 75% had A-->G mutation in the rpsL gene at codon 43. RLBH results showed 96-99% concordance with phenotypic culture results.

CONCLUSION

This is a first attempt at combining speciation with detection of drug resistance to RIF, INH, and STR in MTB for accurate and rapid management of mycobacterial infections as well as for compiling genotypic epidemiological data.

Association between 16S-23S internal transcribed spacer sequence groups of Mycobacterium avium complex and pulmonary disease

Organisms within the Mycobacterium avium complex (MAC) may have differential virulence. We compared 33 subjects with MAC pulmonary disease to 75 subjects with a single positive culture without disease. M. avium isolates were significantly more likely to be associated with MAC pulmonary disease (odds ratio = 5.14, 95% confidence interval = 1.25 to 22.73) than M. intracellulare.

Cavitary pulmonary disease

A pulmonary cavity is a gas-filled area of the lung in the center of a nodule or area of consolidation and may be clinically observed by use of plain chest radiography or computed tomography. Cavities are present in a wide variety of infectious and noninfectious processes. This review discusses the differential diagnosis of pathological processes associated with lung cavities, focusing on infections associated with lung cavities. The goal is to provide the clinician and clinical microbiologist with an overview of the diseases most commonly associated with lung cavities, with attention to the epidemiology and clinical characteristics of the host.

Identification of non-tuberculous mycobacteria from the Central Public Health Laboratory from Mato Grosso do Sul and analysis of clinical relevance

Non-tuberculous mycobacteria isolated at the Central Public Health Laboratory from Mato Grosso do Sul in 2003 and 2004 were identified by conventional phenotypic methods (TI) and by PCR-Restriction Enzyme Analysis (PRA) using the hsp65 gene as target (PRA-hsp65). With 15 of the 32 analysed isolates, results of both methods were concordant, being 8 Mycobacterium avium, 3 M. fortutium, 1 M. kansasii, 1 M. flavescens, 1 M. peregrinum and 1 Nocardia brasiliensis. TI of 12 isolates was inconclusive. Novel PRA-hsp65 patterns were observed with 11 isolates. Medical data were evaluated for inference of clinical relevance of these isolates.

Surgical treatment of pulmonary diseases due to nontuberculous mycobacteria

Although the treatment of pulmonary diseases due to nontuberculous mycobacteria (NTM) requires the long-term use of antibiotics in combination, the treatment success rates are unsatisfactory. We evaluated the clinical characteristics and surgical outcomes of 23 patients with NTM lung diseases who had underwent pulmonary resection. The median age of the patients was 45 yr. Of the 23 patients, 10 had Mycobacterium avium-intracellulare complex infection, 12 had M. abscessus infection, and one had M. xenopi infection. The indications for surgery were antibiotic therapy failure (n=11), remnant cavitary lesion with high probability of relapse (n=8), and massive hemoptysis (n=4). The most common procedure was lobectomy (48%). Postoperative complications occurred in eight patients (35%), including postoperative pneumonia (n=3) and late bronchopleural fistula (n=2). Negative sputum culture conversion was achieved and maintained in all except two mortalities. Although it is associated with a relatively high complication rate, patients with NTM lung disease whose disease is localized to one lung and who can tolerate resectional surgery might be considered for surgery, if there has been poor response to drug therapy or if the patients develop significant disease-related complications such as hemoptysis.

Non-tuberculous mycobacterial infection of the parotid gland in an immunosuppressed adult

Infections of the parotid gland with non-tuberculous mycobacteria (NTM) are rarely described. Here, we report on an infection of the parotid gland caused by Mycobacterium avium and give a literature-based overview about this entity. In the light of a global increase of mycobacterial infections, unusual manifestations have to be considered and should be included in the differential diagnosis when dealing with solid lesions of uncertain aetiology in the head and neck region.

Mycobacterium haemophilum epididymal abscess in a renal transplant patient

Mycobacterium haemophilum is an established cause of cutaneous lesions in immunocompromised hosts. We report the first known case of epididymal abscess, which highlights the need to work up all specimens that are acid-fast bacillus-positive for M. haemophilum from immunocompromised hosts, regardless of body site.

Interleukin-12 receptor beta1 polymorphisms and nontuberculous mycobacterial lung diseases

The pathway involving interferon-gamma and interleukin (IL)-12 plays an important role in host defense against mycobacterial infections. Recent studies have indicated that IL-12 receptor beta1 (IL-12Rbeta1) gene polymorphisms are associated with susceptibility to pulmonary tuberculosis. However, there have been no reports of an association between IL-12Rbeta1 gene polymorphism and lung disease caused by nontuberculous mycobacteria (NTM). The present study involved 128 patients with the nodular bronchiectatic form of NTM lung disease (75 patients with Mycobacterium avium-intracellulare complex infection and 53 patients with Mycobacterium abscessus infection) and 240 healthy controls. Single nucleotide polymorphisms of the IL-12Rbeta1 gene at positions +705A/G, +1158T/C, and +1196G/C were determined by direct sequencing of polymerase chain reaction products. Comparisons of the NTM lung disease patients with healthy controls did not identify any significant differences in relation to the genotype, allele, and haplotype frequencies of the IL-12Rbeta1 +705A/G, +1158T/C, and +1196G/C polymorphisms. These IL-12Rbeta1 gene polymorphisms do not appear to be responsible for host susceptibility to NTM lung disease, at least in this Korean population.

Pulmonary Mycobacterium simiae infection: comparison with pulmonary tuberculosis

To identify the clinical and radiological features distinguishing Mycobacterium simiae respiratory infection from pulmonary tuberculosis, the demographics, underlying conditions, and clinical and radiological findings of 121 consecutive patients with pulmonary tuberculosis and 102 with M. simiae respiratory infection were compared retrospectively. In the M. simiae group, the patients were older (mean age 69 +/- 16 years vs. 47 +/- 21 years, p = 0.0001), with a female predominance (62% vs. 45%, p = 0.008). Only 4% were of Ethiopian origin compared to 25% of the tuberculosis group (p = 0.0001). M. simiae infection was associated with significantly higher rates of smoking history, underlying chronic obstructive pulmonary disease, zero human immunodeficiency virus (HIV) infection compared to 10% in the tuberculosis group (p = 0.001), blunted symptoms, and noncavitary infiltrates in the lower/middle lobes on chest X-ray. HIV-negative patients with M. simiae respiratory infection are distinguishable from patients with pulmonary tuberculosis by several demographic, clinical, and radiological features. These findings have important diagnostic and therapeutic implications.