Host susceptibility factors in mycobacterial infection. Genetics and body morphotype

Association of Toll-like Receptors 1, 2, 4, 6, 8, 9 and 10 Genes Polymorphisms and Susceptibility to Pulmonary Tuberculosis in Sudanese Patients

Background

Genetic factors are important contributors to the development of a wide range of complex disease. Polymorphisms in genes encoding for toll-like receptors (TLRs) usually influence the efficiency of the immune response to infection and are associated with disease susceptibility and progression. Therefore, we aim to describe the first association between TLR1, TLR2, TLR4 TLR6, TLR8, TLR9 and TLR10 genes polymorphisms and susceptibility to pulmonary tuberculosis (PTB) in Sudanese patients.

Methodology

Here we performed a case study which included 160 tuberculosis patients and 220 healthy matched controls from Sudan. In the study population, we evaluated the possible association between 86 markers in TLR1, TLR2, TLR4 TLR6, TLR8, TLR9 and TLR10 genes polymorphisms and susceptibility to PTB disease in Sudanese population using polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP).

Results

From our results it appeared that in the PTB population the TLR1 (rs5743557, rs4833095, rs5743596), TLR2 (rs5743704, rs5743708, rs3804099), TLR4 (rs4986790, rs4986791), TLR6 (rs5743810), TLR8 (rs3764879, rs3764880), TLR9 (rs352165, rs352167, rs187084) and TLR10 (rs4129009) were significantly more often encountered (p<0.0001) than in the control population and were associated with PTB in the Sudanese population. For the other polymorphisms tested, no association with PTB was found in the population tested.

Conclusion

The work describes novel mutations in TLR1, TLR2, TLR4, TLR6, TLR8, TLR9 and TLR10 genes and their association with PTB infection in Sudanese population. These results will enhance our ability to determine the risk of developing the disease by targeting specific TLR pathways to reduce the severity of the disease. Future studies are needed in a larger sample to replicate our findings and understand the mechanism of association of TLR polymorphism in PTB.

Mycobacterium abscessus: It’s Complex

Mycobacterium abscessus (M. abscessus) is an opportunistic pathogen usually colonizing abnormal lung airways and is often seen in patients with cystic fibrosis. Currently, there is no vaccine available for M. abscessus in clinical development. The treatment of M. abscessus-related pulmonary diseases is peculiar due to intrinsic resistance to several commonly used antibiotics. The development of either prophylactic or therapeutic interventions for M. abscessus pulmonary infections is hindered by the absence of an adequate experimental animal model. In this review, we outline the critical elements related to M. abscessus virulence mechanisms, host–pathogen interactions, and treatment challenges associated with M. abscessus pulmonary infections. The challenges of effectively combating this pathogen include developing appropriate preclinical animal models of infection, developing proper diagnostics, and designing novel strategies for treating drug-resistant M. abscessus.

Nontuberculous mycobacterial lung infections in patients with eating disorders: plausible mechanistic links in a case series

Nontuberculous mycobacteria (NTM) are widely distributed in the environment and are almost always acquired into the lungs by bioaerosol inhalation or aspiration of NTM-contaminated water, biofilms, and soil. NTM are increasingly recognized as causes of lung diseases in immunocompetent hosts, a not insignificant number of whom have a life-long or nearly life-long slender body habitus as well as thoracic cage abnormalities such as scoliosis and pectus excavatum. While several hypotheses have been offered to explain the purported increase in susceptibility to NTM lung disease in such individuals, the precise explanation remains unknown. We described three patients with eating disorders associated with severe malnutrition and either purging behaviors or other risks for aspiration who were diagnosed with NTM lung infections-the largest number of such patients to date in a single report. We discuss the clinical and experimental evidence that low body weight and chronic vomiting with attendant jeopardy for aspiration, as seen in patients with eating disorders, may represent risk factors for NTM lung disease. We also speculate the possibility of occult and undiagnosed eating disorders in some of the slender NTM lung disease patients with no known risk factors for the opportunistic infection other than their low body weight.

Association of Toll like receptor 2 and 9 gene variants with pulmonary tuberculosis: exploration in a northern Indian population

Tuberculosis (TB) is a disease of global importance. There is an increasing recognition of the role of Toll like receptors, important pattern recognition receptors of host immune system, in determining the susceptibility or resistance to TB in various populations. In an attempt to examine the importance of Toll like receptors in immune response to Mycobacterium tuberculosis infection, we explored two variants each of TLR2 and TLR9 in a population residing in Uttar Pradesh, India. Genotyping was performed to detect -196 to -174 del polymorphism and G2258A SNP (Arg753Gln, rs5743708) in TLR2 gene and -T1237C (rs5743836) and G2848A (rs352140) SNP in TLR9 gene in patients with pulmonary TB and healthy controls. The A allele of G2848A SNP in TLR9 gene was found with a marginally higher frequency among TB patients as compared to healthy controls, suggesting that A allele at position 2848 of TLR9 gene may be associated with susceptibility to TB in North Indian population [p = 0.05, Mantel-Haenszel OR = 1.34, 95% CI (1.0-1.82)].

Association of Interferon-γ Receptor-1 Gene Polymorphism with Nontuberculous Mycobacterial Lung Infection among Iranian Patients with Pulmonary Disease

Nontuberculous mycobacteria (NTM) cause significant pulmonary infections in humans. Researchers have reported an association between interferon-gamma receptor-1 (IFN-γR1 or IFNGR1) deficiency and susceptibility to NTM, but the relevance of polymorphism within these genes is not yet clear. In this study, a single nucleotide polymorphism (SNP), T to C, at position-56 in NTM patients with pulmonary disease was investigated. Molecular identification of Mycobacterium isolates was performed with hsp65 genes using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Then, the host genomic DNA from confirmed NTM patients (N = 80) and control subjects (N = 80) were screened for SNPs of IFNGR1 (T-56C) by PCR-RFLP. The results indicated that NTM patients had higher TC (26/80; 32.5%) or CC (46/80; 57.5%) genotypes in comparison with control groups (TC genotypes [22/80, 27.5%]; CC genotypes [6/80, 7.5%]) (P < 0.05). In this regard, all the patients infected with rapid-growing Mycobacterium (RGM, i.e., Mycobacterium chelonae and Mycobacterium fortuitum) had CC genotypes (100%). In contrary, only 50.7% (35/69) of infected patients with slow-growing Mycobacterium (i.e., Mycobacterium simiae, Mycobacterium kansasii, and Mycobacterium avium-intracellulare) had CC genotypes. Thus, patients with CC mutation in IFNGR1 at position-56 are more likely to develop RGM infection. In overall, there is a significant association between SNP of IFNGR1 at position-56 and susceptibility to NTM infection. Based on these data, we propose SNP of IFNGR1 at position-56 as a suitable "biomarker" for identifying populations at higher risk of infection.

Protein tyrosine phosphatase nonreceptor type 22 (PTPN22) gene polymorphism in pulmonary tuberculosis in the Indian population

A variant of the protein tyrosine phosphatase nonreceptor type 22 (PTPN22) gene is known to be associated with susceptibility to autoimmune diseases and bacterial infections as it acts as an important regulator of T-cell activation. The objective of this study was to evaluate whether PTPN22-C1858T polymorphism is associated with the resistance to pulmonary tuberculosis (PTB). Single-nucleotide polymorphism of PTPN22-C1858T (rs2476601) was genotyped in 124 patients with PTB and 130 healthy controls from India using restriction fragment length polymorphism and direct sequencing of the amplified DNA. The frequencies of genotypes CC, CT, and TT were 100%, 0%, and 0%, respectively, in PTB; and 99.2%, 0.8% and 0%, respectively, in healthy control individuals. These values did not differ significantly between the patients and controls. The mutant allele C1858T was found to be a rare allele in Indian population.

A genetic perspective on granulomatous diseases with an emphasis on mycobacterial infections

Identification of the genetic factors predisposing to mycobacterial infections has been a subject of intense research activities. Current knowledge of the genetic and immunological basis of susceptibility to mycobacteria largely comes from natural human and experimental models of Bacille Calmette Guérin (BCG) and nontuberculous mycobacterial infections. These observations support the central role of the IL-12/IFN-γ pathway in controlling mycobacterial infection. In this review, we discuss the knowledge that associates both simple and complex inheritance with susceptibility to mycobacterial diseases. We place a special emphasis on monogenic disorders, since these clearly pinpoint pathways and can adduce mechanism. We also describe the clinical, immunological, and pathological features that may steer clinical investigation in the appropriate directions.

Experimental Reactivation of Pulmonary Mycobacterium avium Complex Infection in a Modified Cornell-Like Murine Model

The latency and reactivation of Mycobacterium tuberculosis infection has been well studied. However, there have been few studies of the latency and reactivation of Mycobacterium avium complex (MAC), the most common etiological non-tuberculous Mycobacterium species next to M. tuberculosis in humans worldwide. We hypothesized that latent MAC infections can be reactivated following immunosuppression after combination chemotherapy with clarithromycin and rifampicin under experimental conditions. To this end, we employed a modified Cornell-like murine model of tuberculosis and investigated six strains consisting of two type strains and four clinical isolates of M. avium and M. intracellulare. After aerosol infection of each MAC strain, five to six mice per group were euthanized at 2, 4, 10, 18, 28 and 35 weeks post-infection, and lungs were sampled to analyze bacterial burden and histopathology. One strain of each species maintained a culture-negative state for 10 weeks after completion of 6 weeks of chemotherapy, but was reactivated after 5 weeks of immunosuppression in the lungs with dexamethasone (three out of six mice in M. avium infection) or sulfasalazine (four out of six mice in both M. avium and M. intracellulare infection). The four remaining MAC strains exhibited decreased bacterial loads in response to chemotherapy; however, they remained at detectable levels and underwent regrowth after immunosuppression. In addition, the exacerbated lung pathology demonstrated a correlation with bacterial burden after reactivation. In conclusion, our results suggest the possibility of MAC reactivation in an experimental mouse model, and experimentally demonstrate that a compromised immune status can induce reactivation and/or regrowth of MAC infection.

Investigation of Toll-Like Receptor-2 (2258G/A) and Interferon Gamma (+874T/A) Gene Polymorphisms among Infertile Women with Female Genital Tuberculosis

BACKGROUND

Toll-like receptor 2 (TLR2) and interferon-gamma (IFN-γ) coordinate with a diverse array of cellular programs through the transcriptional regulation of immunologically relevant genes and play an important role in immune system, reproductive physiology and basic pathology. Alterations in the functions of TLR2 2258G (guanine)/ A, IFN-γ (+874T/A) and signalling molecules that result from polymorphisms are often associated with susceptibility or resistance, which may, in turn, establish the innate host response to various infectious diseases. Presently, we proposed to investigate the risk of common single nucleotide polymorphism (SNP) of TLR2 and IFN-γ genes, for their effect on infertility in women with female genital tuberculosis (FGTB) and healthy women as controls.

METHODOLOGY/PRINCIPAL FINDINGS

Genotyping of TLR2 and IFN-γ gene polymorphisms was performed by amplification refractory mutation system multi-gene/multi-primer polymerase chain reaction followed by restriction fragment length polymorphism in 175 FGTB patients and 100 healthy control women (HCW). The TLR2 polymorphism [adenine (A) allele] was observed in 57.7 and 58.0% of FGTB patients and HCW, respectively. The IFN-γ (+874T/A) polymorphism (A allele) was significant in 74.3 and 71.0% of FGTB patients and HCW, respectively, while the odds ratios for the AA and TA genotypes for predisposition of FGTB were found to be 0.304 and 1.650 in HCW, respectively. The SNP of TLR2 was not associated with FGTB but the SNP of IFN-γ was found to be associated with mycobacteria infections and to induce infertility.

CONCLUSIONS/SIGNIFICANCE

At present, we hypothesize that infertile women with FGTB and HCW without tuberculosis (TB) have identical frequency of TLR variants, which may be adequate in the production of IFN-γ in response to Mycobacterium tuberculosis infections. Thus, the study appears to be the first of its kind reporting a mutation in the IFN-γ gene [+874 T (thymine) to A] responsible for susceptibility to TB infections and further inducing infertility.

Host susceptibility to non-tuberculous mycobacterial infections

Non-tuberculous mycobacteria cause a broad range of clinical disorders, from cutaneous infections, such as cervical or intrathoracic lymphadenitis in children, to disseminated infections at all ages. Recognition of the underlying immune defect is crucial for rational treatment, preventive care, family screening, and, in some cases, transplantation. So far, at least seven autosomal mutations (in IL12B, IL12RB1, ISG15, IFNGR1, IFNGR2, STAT1, and IRF8) and two X-linked mutations (in IKBKG and CYBB), mostly presenting in childhood, have been reported to confer susceptibility to disseminated non-tuberculous mycobacterial infection. GATA2 deficiency and anti-interferon γ autoantibodies also give rise to disseminated infection, typically in late childhood or adulthood. Furthermore, isolated pulmonary non-tuberculous mycobacterial infection has been increasing in prevalence in people without recognised immune dysfunction. In this Review, we discuss how to detect and differentiate host susceptibility factors underlying localised and systemic non-tuberculous mycobacterial infections.

Severe vitamin D deficiency is associated with non-tuberculous mycobacterial lung disease: a case-control study

BACKGROUND AND OBJECTIVE

Previous studies have found evidence of an association between tuberculosis and vitamin D deficiency (VDD). However, the association between VDD and infection caused by non-tuberculous mycobacteria (NTM) has never been studied. This study evaluated the prevalence and severity of VDD in NTM lung disease and attempted to identify predictive factors.

METHODS

Age- and sex-matched case-control study was conducted to assess the prevalence and severity of VDD in patients with NTM lung disease.

RESULTS

After adjusting for potential confounding factors, the adjusted mean serum level of 25-hydroxyvitamin D (25(OH)D) levels was lower in 104 patients with NTM lung disease (10.7 ng/mL, 95% confidence interval (CI) 4.5-16.8 ng/mL) than that of 312 controls (13.7 ng/mL, 95% CI 7.4-19.5 ng/mL) (P = 0.012). Although the prevalence of VDD defined as serum 25(OH)D level <20 ng/mL was not different, severe VDD defined as serum 25(OH)D level <10 ng/mL was more prevalent in patients (P < 0.001). In multivariate analysis, severe (but not mild) VDD was independently associated with NTM lung disease (adjusted odds ratio 3.9, 95% CI 1.9-8.5, P < 0.001).

CONCLUSIONS

Patients with NTM lung disease have a high prevalence of severe VDD and VDD was independently associated with NTM lung disease. Further studies are needed to examine causality.

Changes in serum immunomolecules during antibiotic therapy for Mycobacterium avium complex lung disease

Little information is available regarding changes in immune status for patients with Mycobacterium avium complex (MAC) lung disease during antibiotic therapy. Serum immunomolecules from 42 patients with MAC lung disease were assayed comparatively using an array-based system according to (i) patients with MAC lung disease at the time of diagnosis versus healthy controls and (ii) alterations after 12 months of antibiotic therapy in the MAC lung disease group. In addition, cytokine analyses were performed to determine whether cytokine responses were associated specifically with the disease phenotype, treatment outcome and aetiological agent. Notably, the serum concentrations of type 1 cytokine-associated molecules, such as CD40L, interferon (IFN)-γ, interleukin (IL)-8 and IL-23, were decreased significantly in patients at the time of diagnosis, suggesting that these molecules may serve as indicators of host susceptibility to MAC disease. Although the overall serum level of T helper type 1 (Th1)-related molecules, such as CD40L and IFN-γ, was restored after treatment, Th17-related cytokines, such as IL-17 and IL-23, were down-regulated significantly at 12 months post-treatment compared to pretreatment. Furthermore, these cytokine patterns differed among patient subgroups. Decreased serum concentrations of IL-17 and/or IL-23 were associated with failure of sputum conversion, the fibrocavitary disease phenotype and M. intracellulare lung disease. Thus, the reciprocal balance between Th1 and Th17 immunity during antibiotic therapy for MAC lung disease is critical for dictating the treatment response. In conclusion, a low level of Th1-related immunomolecules may perpetuate MAC lung disease, and the serum concentrations of Th17-related cytokines can reflect the treatment outcome, disease phenotype and aetiological agent.

Management of nontuberculous mycobacterial infection in the elderly

The incidence of nontuberculous mycobacteria (NTM) has increased over the last decades. Elderly people are more susceptible to NTM and experience increased morbidities. NTM incidence is expected to rise due to an increasing elderly population at least up to 2050. Given the importance of NTM infection in the elderly, an increasing interest exists in studying NTM characteristics in the aged population. In this review, we summarize the characteristics of NTM infection among elderly patients. We focus on epidemiology, clinical presentation, and treatment options of NTM in this age group. We highlight the differences in the diagnosis and treatment between rapid and slow growing mycobacterial infections. The current recommendation for treatment of NTM is discussed. We debate if in vitro susceptibility testing has a role in the treatment of NTM. Drug-drug interaction between antibiotics used to treat NTM and other medications, particularly warfarin, is another important issue that we discuss. Finally, we review the prognosis of NTM disease in elderly patients.

Complement C4 deficiency--a plausible risk factor for non-tuberculous mycobacteria (NTM) infection in apparently immunocompetent patients

Background

Non-tuberculous mycobacteria (NTM) are ubiquitous in the environment and they infect mainly persons with underlying pulmonary diseases but also previously healthy elderly women. Defects in host resistance that lead to pulmonary infections by NTM are relatively unknown. A few genetic defects have been associated with both pulmonary and disseminated mycobacterial infections. Rare disseminated NTM infections have been associated with genetic defects in T-cell mediated immunity and in cytokine signaling in families. We investigated whether there was an association between NTM infections and deficiencies of complement components C4A or C4B that are encoded by major histocompatibility complex (MHC).

Methods

50 adult patients with a positive NTM culture with symptoms and findings of a NTM disease were recruited. Patients' clinical history was collected and symptoms and clinical findings were categorized according to 2007 diagnostic criteria of The American Thoracic Society (ATS). To investigate the deficiencies of complement, C4A and C4B gene copy numbers and phenotype frequencies of the C4 allotypes were analyzed. Unselected, healthy, 149 Finnish adults were used as controls.

Results

NTM patients had more often C4 deficiencies (C4A or C4B) than controls (36/50 [72%] vs 83/149 [56%], OR = 2.05, 95%CI = 1.019–4.105, p = 0.042). C4 deficiencies for female NTM patients were more common than for controls (29/36 [81%] vs 55/100 [55%], OR = 3.39, 95% CI = 1.358–8.460, p = 0.007). C4 deficiences seemed not to be related to any specific underlying disease or C4 phenotype.

Conclusions

C4 deficiency may be a risk factor for NTM infection in especially elderly female patients.

R620W functional polymorphism of protein tyrosine phosphatase non-receptor type 22 is not associated with pulmonary tuberculosis in Zahedan, southeast Iran

The protein tyrosine phosphatase non-receptor type 22 (PTPN22) gene, which encodes an intracellular lymphoid-specific phosphatase, is considered an important regulator of T-cell activation. We investigated a possible association between the PTPN22 C1858T (R620W) polymorphism and pulmonary tuberculosis in an Iranian population. Single nucleotide polymorphisms of PTPN22 C1858T (rs2476601) were genotyped in 172 pulmonary tuberculosis cases and 204 normal subjects from Zaheden, Iran. Frequencies of genotypes CC, CT and TT of the PTPN22 C1858T polymorphism were 98.3, 1.7 and 0% in the pulmonary tuberculosis patients, and 96.1, 3.9 and 0% in the control group, respectively (P = 0.239). The frequency of the minor (T) allele was 0.8% in pulmonary tuberculosis patients and 2.0% in controls. Significant differences were not observed in genotype or allele frequencies of PTPN22 C1858T in the comparison between pulmonary tuberculosis patients and healthy subjects in our Iranian population sample.

Impaired Expression of MAPK Is Associated with the Downregulation of TNF-α, IL-6, and IL-10 in Mycobacterium abscessus Lung Disease

Background

Healthy individuals who develop nontuberculous mycobacteria (NTM) lung disease are likely to have specific susceptibility factors which can lead to a NTM infection. The aim of the present study was to investigate the mechanism underlying innate immune responses, including the role of mitogen-activated protein kinase (MAPK), in Mycobacterium abscessus lung disease.

Methods

Extracellular signal-regulated kinase (ERK1/2) and p38 MAPK expression in monocytes from peripheral blood mononuclear cells were measured by Western blot analysis after stimulation by Mycobacterium avium in five patients with M. abscessus lung disease and seven healthy controls. A M. avium-induced cytokine assay was performed after inhibition of ERK1/2 and p38 MAPK pathways.

Results

Mycobacterium avium induced p38 and ERK1/2 expression in monocytes from healthy controls and subsequently upregulated tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 production. In monocytes from patients with M. abscessus lung disease, however, induction of p38 and ERK1/2 expression, and the production of TNF-α, IL-6, and IL-10 were significantly lower.

Conclusion

Decreased activity of MAPK and cytokine secretion in monocytes from patients with M. abscessus lung disease may provide an explanation regarding host susceptibility to these uncommon infections.

Análise de restrição enzimática do gene hsp65 de isolados clínicos de pacientes com suspeita de tuberculose pulmonar em Teresina, Piauí

OBJETIVO: Identificar as espécies de micobactérias encontradas no escarro de pacientes com suspeita de tuberculose pulmonar e analisar o impacto dessas identificações na abordagem terapêutica. MÉTODOS: Foram avaliados 106 pacientes com suspeita de tuberculose pulmonar encaminhados para o serviço de pneumologia de um hospital público em Teresina, Piauí. Espécimes de escarro matinal foram avaliados quanto à presença de micobactérias por baciloscopia e cultura. Foram utilizadas PCR e análise de restrição enzimática do gene hsp65 (PRA-hsp65) para a identificação das cepas de micobactérias isoladas em cultura. RESULTADOS: Foram analisadas 206 amostras de escarro. A idade dos pacientes variou de 15 a 87 anos, sendo 67% do gênero masculino. Tosse ocorreu em 100% dos casos. O padrão radiográfico predominante foi de lesão moderada, observada em 70%. A positividade no esfregaço foi de 76%, e isolamento em cultura ocorreu em 91% das culturas executadas. Testes tradicionais identificaram micobactérias não tuberculosas (MNT) em 9% dos isolados. O método PRA-hsp65 confirmou esses dados, mostrando sete padrões de bandas capazes de identificar as espécies de MNT isoladas: Mycobacterium kansasii; M. abscessus 1; M. abscessus 2; M. smegmatis; M. flavescens 1; M. gordonae 5 e M. gordonae 7. Todos os pacientes com MNT tinham mais de 60 anos, e observaram-se bronquiectasias em 88% das radiografias. Houve dois casos de reinfecção, identificados inicialmente como infecção por M. abscessus e M. kansasii. CONCLUSÕES: As MNT causam infecção pulmonar em pacientes imunocompetentes, e a identificação das MNT é importante para estabelecer o diagnóstico correto e a decisão terapêutica mais adequada. O método PRA-hsp65 é útil para identificar espécies de MNT e pode ser implantado em laboratórios de biologia molecular não especializados em micobactérias.

Slender, older women appear to be more susceptible to nontuberculous mycobacterial lung disease

BACKGROUND

Nontuberculous mycobacteria (NTM) are environmental microbes that are associated with a variety of human diseases, particularly chronic lung infections. Over the past several decades, NTM lung disease has been increasingly seen in postmenopausal women with slender body habitus.

OBJECTIVE

This article reviewed the clinical and experimental evidence that supports the observation that thin older women (aged 50-80 years) are predisposed to NTM lung disease. We posited 3 potential pathways for this predisposition: relative estrogen deficiency, abnormal levels of adipokines that alter immune responses, and abnormal expression of transforming growth factor-beta (TGF-beta) related to fibrillin anomalies similar to Marfan syndrome (MFS).

METHODS

Using the PubMed database, a literature search was performed (all publications up to July 2009) by pairing the key phrase nontuberculous mycobacteria with weight, malnutrition, female gender, body habitus, leptin, adipokines, estrogen, menopause, postmenopausal, or body mass index. Non-English-language articles were included if their abstracts were in English. Relevant articles were also identified from the abstracts.

RESULTS

Published case reports and series indicate that in the past 20 years, NTM lung disease has been recognized in disproportionately increased numbers in postmenopausal women. Among these patients, slender body habitus and thoracic cage abnormalities, such as pectus excavatum and scoliosis, are commonly described. Notably, no long-term prospective clinical studies exist to corroborate that low weight is an independent risk factor for NTM lung disease. However, based on the findings of a limited number of experimental studies, we hypothesize that decreased leptin, increased adiponectin, and/or decreased estrogen in older women with slender body habitus may account for their increased susceptibility to NTM infections. We further speculate that in some patients with features mindful of MPS (slender, scoliosis, pectus excavatum, or mitral valve prolapse), there may be anomalies of fibrillin, similar to MFS, that lead to the expression of the immunosuppressive cytokine TGP-beta further increasing their susceptibility to NTM.

CONCLUSIONS

It is likely that both sufficient environmental exposure and host susceptibility are required for the establishment of NTM lung disease. The observation that NTM lung infections are more common in slender, older women without any overt immune defects suggests that abnormal expression of adipokines, sex hormones, and/or TGF-beta may play an important role in their susceptibility.

Host immune response to rapidly growing mycobacteria, an emerging cause of chronic lung disease

Rapidly growing mycobacteria (RGM) are environmental organisms classified under the broader category of nontuberculous mycobacteria. The most common RGM to cause human diseases are Mycobacterium abscessus, Mycobacterium chelonae, Mycobacterium fortuitum, and Mycobacterium massiliense. Infections due to the RGM are an emerging health problem in the United States. Chronic pulmonary disease and skin/soft-tissue infections are the two most common disorders due to these organisms. Clinical outcomes in the treatment of M. abscessus infections are generally disappointing. Because less is known about the nature of the immune response to M. abscessus than for tuberculosis, we herein highlight the major clinical features associated with infections due to M. abscessus and other RGM, and review the known host immune response to RGM, drawing from experimental animal and clinical studies. Based on in vitro and in vivo murine models, Toll-like receptor 2, dectin-1, tumor necrosis factor (TNF)-α, IFN-γ, leptin, T cells, and possibly neutrophils are important components in the host defense against RGM infections. However, excessive induction of TNF-α by the R morphotype of M. abscessus may allow it to be more pathogenic than the S morphotype. Clinical observations and/or genetic studies in humans corroborate many of the findings in animals in that those with cell-mediated immunodeficiency, genetic defects in IFN-γ-IL-12 axis, and those individuals on TNF-α blockers are at increased risk for nontuberculous mycobacteria infections, including the RGM. However, much remains to be discovered on why seemingly healthy individuals, particularly slender postmenopausal women with thoracic cage anomalies, appear to be at increased risk.

HLA antigens and nontuberculous mycobacterial lung disease in Korean patients

BACKGROUND

Human leukocyte antigen (HLA) molecules are known to play an important role in host-defense mechanisms. The aim of this study was to evaluate the association between HLA alleles and lung disease caused by nontuberculous mycobacteria (NTM) in Korean patients.

METHODS

Seventy-eight patients with NTM lung disease (48 patients with Mycobacterium avium-intracellulare complex [MAC] infection and 30 patients with Mycobacterium abscessus infection) were included in the study. HLA-A, -B, and -DRB1 genotyping was performed by polymerase chain reaction using sequence-specific primers. Data from 485 healthy Korean individuals were used as a control.

RESULTS

When compared to controls, patients with NTM lung disease showed an increased frequency of DRB1*11 (OR = 1.91, 95% confidence interval [CI] = 1.01-3.64, p = 0.045, corrected p [pC] > 0.05). In the subgroup analysis, patients with MAC lung disease had an increased frequency of B*46 (OR = 2.23, 95% CI = 1.05-4.73, p = 0.044, pC > 0.05).

CONCLUSIONS

Our data suggest that in a Korean population, patients with NTM lung disease and healthy subjects differ in the frequencies of some HLA alleles. However, when considering corrected p values, our findings are inconclusive.

Acute forms of tuberculosis in adults

Although typically considered a chronic disease, tuberculosis (TB) has protean acute manifestations, the major forms of which are reviewed in this article. The pathogenesis of acute TB, although still incompletely understood, may be related to both epidemiologic and genetic host factors. Miliary TB manifests as a nonspecific clinical syndrome with a high mortality rate. The most well-known form of acute TB is meningitis, characterized by fever, nuchal rigidity, and a lymphocytic pleocytosis of the cerebrospinal fluid. Acute abdominal TB may present with obstruction or less commonly as perforated viscus or peritonitis. Critically ill patients may have acute respiratory distress syndrome, shock, or disseminated intravascular coagulopathy. The spectrum of disease makes diagnosis of acute TB difficult unless clinical suspicion of disease is high, but the high mortality mandates its consideration. Early initiation of therapy is crucial to optimize clinical outcome.

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.

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.

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.

Adjuvant interferon gamma in patients with pulmonary atypical Mycobacteriosis: a randomized, double-blind, placebo-controlled study

BACKGROUND

High antibiotic resistance is described in atypical Mycobacteriosis, mainly by Mycobacterium avium complex (MAC).

METHODS

A randomized, double-blind, placebo-controlled clinical trial was carried out in two hospitals to evaluate the effect of interferon (IFN) gamma as immunoadjuvant to chemotherapy on patients with atypical mycobacteria lung disease. Patients received placebo or 1 x 106 IU recombinant human IFN gamma intramuscularly, daily for one month and then three times per week up to 6 months as adjuvant to daily oral azithromycin, ciprofloxacin, ethambutol and rifampin. Sputum samples collection for direct smear observation and culture as well as clinical and thorax radiography assessments were done during treatment and one year after. Cytokines and oxidative stress determinations were carried out in peripheral blood before and after treatment.

RESULTS

Eighteen patients were included in the IFN group and 14 received placebo. Groups were homogeneous at entry; average age was 60 years, 75% men, 84% white; MAC infection prevailed (94%). At the end of treatment, 72% of patients treated with IFN gamma were evaluated as complete responders, but only 36% in the placebo group. The difference was maintained during follow-up. A more rapid complete response was obtained in the IFN group (5 months before), with a significantly earlier improvement in respiratory symptoms and pulmonary lesions reduction. Disease-related deaths were 35.7% of the patients in the placebo group and only 11.1% in the IFN group. Three patients in the IFN group normalized their globular sedimentation rate values. Although differences in bacteriology were not significant during the treatment period, some patients in the placebo group converted again to positive during follow-up. Significant increments in serum TGF-beta and advanced oxidation protein products were observed in the placebo group but not among IFN receiving patients. Treatments were well tolerated. Flu-like symptoms predominated in the IFN gamma group. No severe events were recorded.

CONCLUSION

These data suggest that IFN gamma is useful and well tolerated as adjuvant therapy in patients with pulmonary atypical Mycobacteriosis, predominantly MAC. Further wider clinical trials are encouraged.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN70900209.

Mycobacterium ulcerans infection as a cause of chronic diarrhea in an AIDS patient: A case report

Chronic diarrhea is one of the most frequent gastro-intestinal manifestations in acquired immunodeficiency syndrome (AIDS). Protozoa and nontuberculous mycobacteria (NTM) are opportunistic pathogens that can easily infect these patients. Among the NTM, Mycobacterium avium complex (MAC) is the most frequently observed pathogen in HIV-infected patients. However, NTMs other than MAC have not been reported as a gastrointestinal pathogen as yet. We present a case of chronic diarrhea in an AIDS patient in whom Mycobacterium ulcerans and cryptosporidium co-infection is evidenced from colonic tissue.

Prevalence of Gastroesophageal Reflux Disease in Patients With Nontuberculous Mycobacterial Lung Disease

BACKGROUND

Knowledge of the relationship between respiratory disorders and gastroesophageal reflux disease (GERD) is increasing. However, the association between GERD and pulmonary disease caused by nontuberculous mycobacteria (NTM) has not been studied in detail. We investigated the prevalence of GERD in patients with the nodular bronchiectatic form of NTM lung disease.

METHODS

Fifty-eight patients with the nodular bronchiectatic form of NTM lung disease underwent ambulatory 24-h esophageal pH monitoring. Of the 58 patients, 27 patients were identified as having Mycobacterium avium complex infection (15 with Mycobacterium intracellulare and 12 with M avium), and 31 patients had Mycobacterium abscessus pulmonary infection.

RESULTS

The prevalence of GERD in patients with the nodular bronchiectatic form of NTM lung disease was 26% (15 of 58 patients). Only 27% (4 of 15 patients) had typical GERD symptoms. No statistically significant differences were found between patients with GERD and those without GERD with regard to age, sex, body mass index, or pulmonary function test results. However, patients with GERD were more likely to have a sputum smear that was positive for acid-fast bacilli (12 of 15 patients, 80%), compared with patients without GERD (19 of 43 patients, 44%) [p = 0.033]. In addition, bronchiectasis and bronchiolitis were observed in more lobes in patients with GERD than in patients without GERD (p = 0.008 and p = 0.005, respectively).

CONCLUSIONS

Patients with the nodular bronchiectatic form of NTM lung disease have a high prevalence of increased esophageal acid exposure, usually without typical GERD symptoms.

Interferon-γ gene+874T–A polymorphism is associated with tuberculosis and gamma interferon response

Interferon-gamma is the most important cytokine in resistance to mycobacterial diseases and common variants of interferon-gamma gene could be related to tuberculosis susceptibility. We tested the hypothesis that the interferon-gamma+874T-A polymorphism is associated with tuberculosis disease, and affects the interferon-gamma response. We determined by pyrosequencing the distribution of the interferon-gamma+874T-A polymorphism in a Turkish population of 319 patients with pulmonary tuberculosis, 42 children with severe forms of tuberculosis and 115 healthy donors. We also analysed whether any correlation exists between this polymorphism and interferon-gamma response to Mycobacterium tuberculosis antigens by ELISPOT in 58 pulmonary tuberculosis cases, and the results were analysed according to the genotypes. We found that the minor allele (T) frequency was significantly lower in patients with pulmonary tuberculosis when compared to controls (P=0.024, OR=0.7), a similarly significant decrease in the frequency of TT genotype was observed in patients with pulmonary tuberculosis, compared to the control group (P=0.02, OR=0.49). IFN-gamma responses to PPD antigen in TT genotype was found to be significantly higher than the AA group (P>0.001). Non-parametric correlation analysis of ELISPOT data showed significant reverse correlation in PPD, CFP10 and ESAT6 values and IFN-gamma +874 genotypes. These results show that the IFN-gamma +874T-A polymorphism is related to the IFN-gamma response and the magnitude of the response decreases during transition from TT- to TA and to AA genotypes. Our data suggest that similar to various Caucasian populations, in a Turkish population the IFN-gamma+874 T-A polymorphism is also associated with tuberculosis disease and affects the magnitude of the IFN-gamma response.

Polymorphisms of interferon-gamma and interferon-gamma receptor 1 genes and non-tuberculous mycobacterial lung diseases

Interferon-gamma (IFN-gamma) is crucial for host defense against mycobacterial infections. Recent studies have indicated that IFN-gamma and IFN-gamma receptor 1 (IFN-gammaR1) gene polymorphisms are associated with susceptibility to pulmonary tuberculosis. The aim of this study was to test the hypothesis that IFN-gamma and IFN-gammaR1 gene polymorphisms influence susceptibility to lung disease caused by non-tuberculous mycobacteria (NTM). Seventy-six patients with the nodular bronchiectatic form of NTM lung disease (37 patients with Mycobacterium avium complex infection and 39 patients with Mycobacterium abscessus infection) and 80 controls were included. Polymorphisms of the IFN-gamma gene at position +874 were determined by the amplification refractory mutation system (ARMS) polymerase chain reaction assay and IFN-gammaR1 gene at positions -611, -270, -56 and +95 was genotyped by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry using genomic DNA. IFN-gammaR1 -270 and +95 polymorphisms were not present in any of the patients or controls. The patients with NTM lung disease showed no significant difference from controls in genotype and allele frequencies of the IFN-gamma +874 and IFN-gammaR1 -611 and -56 polymorphisms. The IFN-gamma +874 and IFN-gammaR1 -611 and -56 polymorphisms do not appear to be responsible for host susceptibility to NTM lung disease, at least in the Korean population.

Prospective analysis of cystic fibrosis transmembrane regulator mutations in adults with bronchiectasis or pulmonary nontuberculous mycobacterial infection

BACKGROUND

Bronchiectasis and pulmonary infection with nontuberculous mycobacteria (NTM) may be associated with disease-causing mutations in the cystic fibrosis transmembrane regulator (CFTR).

METHODS

Fifty adult patients at Stanford University Medical Center with a diagnosis of bronchiectasis and/or pulmonary NTM infection were prospectively characterized by sweat chloride measurement, comprehensive mutational analysis of CFTR, and sputum culture results.

RESULTS

A de novo diagnosis of cystic fibrosis (CF) was established in 10 patients (20%). Patients with CF were more likely than those without CF to have mucus plugging seen on chest high-resolution CT, and women with a CF diagnosis were thinner, with a significantly lower mean body mass index than the non-CF subjects. Thirty CFTR mutations were identified in 24 patients (50% prevalence). Sweat chloride concentration was elevated > 60 mEq/dL (diagnostic of CF) in seven patients (14%), and from 40 to 60 mEq/dL in eight patients (16%). The frequency of CFTR mutations was elevated above that expected in the general population: heterozygous DeltaF508 (12% vs 3%), R75Q (14% vs 1%), and intron 8 5T (17% vs 5 to 10%). Other known CFTR mutations identified were V456A, G542X, R668C, I1027T, D1152, R1162L, W1282X, and L183I. Three novel CFTR mutations were identified: A394V, F650L, and C1344S.

CONCLUSIONS

Mutations in CFTR that alter RNA splicing and/or functional chloride conductance are common in this population, and are likely to contribute to the susceptibility and pathogenesis of adult bronchiectasis and pulmonary NTM infection. Careful clinical evaluation for disease cause should be undertaken in this clinical context.

Partial interferon-gamma receptor deficiency and non-tuberculous mycobacterial lung disease

Interferon-gamma (IFN-gamma) plays a key role in the host defense response against mycobacterial disease, and a complete or partial deficiency in IFN-gamma receptor 1 (IFN-gammaR1) or IFN-gamma receptor 2 (IFN-gammaR2) has been reported to contribute to susceptibility to disseminated infection with non-tuberculous mycobacteria (NTM). However, IFN-gammaR1 and IFN-gammaR2 deficiencies have not yet been studied in adult patients with isolated NTM lung disease. The purpose of the present study was to evaluate whether partial IFN-gammaR1 and IFN-gammaR2 deficiency are associated with human susceptibility to NTM lung disease. We studied 40 patients with NTM lung disease (Mycobacterium avium complex infection, 20 patients; Mycobacterium abscessus infection, 20 patients) for partial IFN-gammaR1 and IFN-gammaR2 deficiency. Genomic DNA was amplified by polymerase chain reaction and sequenced for revealing mutations of the IFN-gammaR1 and IFN-gammaR2 gene. None of the patients had previously reported homozygous recessive missense mutation causing an amino-acid substitution in the extracellular domain of the receptor (I87T) and hotspot for small deletions (818delT, 818del4) of the IFN-gammaR1 or homozygous missense mutation (R114C) of the IFN-gammaR2. In conclusion, in adult patients with isolated NTM lung disease, there is no evidence for previously known genetic defects of partial deficiencies of IFN-gammaR1 and IFN-gammaR2 to correlate with disease.

Toll-like receptor 2 polymorphisms and nontuberculous mycobacterial lung diseases

To investigate the occurrence of the Toll-like receptor 2 (TLR2) polymorphisms in patients with pulmonary disease caused by nontuberculous mycobacteria (NTM), TLR2 Arg677Trp and Arg753Gln polymorphisms were examined. TLR2 polymorphisms do not appear to be responsible for host susceptibility to NTM lung disease, at least in the Korean population.

Lung Disease Due to the More Common Nontuberculous Mycobacteria

As the prevalence of tuberculosis (TB) declines in the developed world, the proportion of mycobacterial lung disease due to nontuberculous mycobacteria (NTM) is increasing. It is not clear whether there is a real increase in prevalence or whether NTM disease is being recognized more often because of the introduction of more sensitive laboratory techniques, and that more specimens are being submitted for mycobacterial staining and culture as the result of a greater understanding of the role of NTM in conditions such as cystic fibrosis, posttransplantation and other forms of iatrogenic immunosuppression, immune reconstitution inflammatory syndrome, fibronodular bronchiectasis, and hypersensitivity pneumonitis. The introduction of BACTEC liquid culture systems (BD; Franklin Lakes, NJ) and the development of nucleic acid amplification and DNA probes allow more rapid diagnosis of mycobacterial disease and the quicker differentiation of NTM from TB isolates. High-performance liquid chromatography, polymerase chain reaction, and restriction fragment length polymorphism analysis have helped to identify new NTM species. Although treatment regimens that include the newer macrolides are more effective than the earlier regimens, failure rates are still too high and relapse may occur after apparently successful therapy. Moreover, treatment regimens are difficult to adhere to because of their long duration, adverse effects, and interactions with the other medications that these patients require. The purpose of this article is to review the common presentations of NTM lung disease, the conditions associated with NTM lung disease, and the clinical features and treatment of the NTM that most commonly cause lung disease.

Non-tuberculous mycobacteria disease as a cause of hospitalization in HIV-infected subjects

OBJECTIVES

The present study characterized and determined the prevalence of mycobacterial diseases (tuberculosis (TB) and non-tuberculous mycobacteria (NTM)) as a cause of hospitalization among HIV-infected subjects consecutively admitted to a large metropolitan hospital during 2001/2002.

METHODS

Hospital discharge diagnoses were established for 521 HIV-positive patients.

RESULTS

Respiratory disease accounted for 49% of the admissions. Community acquired pneumonia (CAP) was the main cause of respiratory disease (52%) followed by Pneumocystis carinii (PCP, 24%), non-tuberculous mycobacteria (NTM, 11%) and Mycobacterium tuberculosis (TB, 9%). Mycobacterium tuberculosis disease was established using bacteriological, clinical and radiographic criteria. NTM disease was defined following the American Thoracic Society criteria. NTM was disseminated in the majority of cases (19 Mycobacterium avium complex (MAC), one Mycobacterium kansasii). Nine patients had respiratory disease (seven MAC, one Mycobacterium fortuitum, one Mycobacterium kansasii) and one had gastrointestinal disease caused by MAC. Mortality was 10% for NTM disseminated cases; none of the TB patients died over the course of the study. The length of hospitalization for NTM patients was longer (15+/-13 days) than for other respiratory cases (10+/-10, p=0.04).

CONCLUSIONS

NTM disease along with its related mortality is a significant pathology as a cause of hospitalization among HIV-infected individuals.

NRAMP1 gene polymorphism and susceptibility to nontuberculous mycobacterial lung diseases

STUDY OBJECTIVES

Pulmonary disease caused by nontuberculous mycobacteria (NTM) may occur in patients with no underlying lung disease and no known immunodeficiency. The purpose of this study was to evaluate a potential role for natural-resistance-associated macrophage protein 1 (NRAMP1) gene polymorphisms for human susceptibility to the NTM lung disease.

DESIGN

A case-control study.

SETTING

Tertiary university medical center.

PARTICIPANTS

Forty-one adult patients with NTM lung disease (Mycobacterium avium complex infection, 18 patients; Mycobacterium abscessus infection, 23 patients) were included in the study population. The diagnosis of NTM lung disease was made when the patients fulfilled the diagnostic criteria published by the American Thoracic Society. All patients had findings on high-resolution CT scans, such as bilateral bronchiectasis combined with multiple small nodules and branching linear structures, that were characteristic of the nodular bronchiectatic form of NTM lung disease. Fifty healthy individuals were selected as control subjects.

RESULTS

Heterozygotes at intron 4 (469 + 14G/C) [INT4], codon 543 in exon 15 (D543N), and 3' untranslated region (3'UTR) were observed at significantly higher frequencies in patients with NTM lung disease than in control subjects. The odds ratios (ORs) were 2.78 (95% confidence interval [CI], 1.12 to 6.89; p = 0.026) for INT4 G/C, 5.74 (95% CI, 1.48 to 22.30; p = 0.006) for D543 G/A, and 9.54 (95% CI, 2.49 to 36.53; p < 0.001) for 3'UTR TGTG+/del. Subjects who were heterozygous for two NRAMP1 polymorphisms in INT4 and D543N were particularly overrepresented among those with NTM lung disease, compared with those with the most common NRAMP1 genotype (OR, 10.88, 95% CI, 1.18 to 100.45; p = 0.035). There were no significant differences in the frequencies of INT4, D543N, and 3'UTR polymorphisms between the patients with M avium complex infection and those with M abscessus infection.

CONCLUSIONS

These findings suggest that the NRAMP1 genetic polymorphisms are associated with human susceptibility to NTM lung disease.

Usefulness of various antibiotics against Mycobacterium avium-intracellulare, measured by their mutant prevention concentration

This study looked the selection of resistant mutants in Mycobacterium avium-intracellulare during antibiotic treatment. The mutant prevention concentration (MPC) of 20 Mycobacterium avium and 12 Mycobacterium intracellulare isolates was determined. Fifty percent of Mycobacterium avium strains had MPC (MPC50) values lower than 16, 64, 40, 55 and 60 mg/L for rifabutin, rifampicin, ciprofloxacin, levofloxacin and moxifloxacin, respectively. In the case of Mycobacterium intracellulare, 50% had MPC (MPC50) values below 60, 30, 35, 16, 2.5 and 14 mg/L for linezolid, rifabutin, levofloxacin, gatifloxacin, moxifloxacin and clarithromycin, respectively. The high capacity for selecting resistant mutants of all the antibiotics studied emphasises the need to restore the immune system if necessary and to administer combined treatments in order to cure patients.

Variable presentation of disseminated nontuberculous mycobacterial infections in a family with an interferon-gamma receptor mutation

A previously healthy 13-year-old child who had disseminated Mycobacterium avium infection is described. Further history revealed disseminated mycobacterial infections in the patient's father and uncle, starting at 9 years old and 1 year old, respectively. Autosomal dominant interferon- gamma receptor mutation was subsequently identified. Clinical variability among the affected members of the same family is consistent with previous reports suggesting substantial variability in the clinical course of this disorder.

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.

Pulmonary disease caused by rapidly growing mycobacteria

The rapidly growing mycobacteria (RGM) differ from slow-growing mycobacteria such as Mycobacterium tuberculosis by virtue of their more rapid growth in culture media and their in vitro resistance to standard antituberculosis drugs. The RGM can produce numerous infections including chronic lung disease. The most common causes of pulmonary disease are Mycobacterium abscessus and Mycobacterium fortuitum. This article reviews the management of patients with lung disease caused by RGM.