Nontuberculous Mycobacteria Group Research Articles

Complete genome sequences and multidrug resistance genotypes of nontuberculous mycobacteria isolates from the Central Tuberculosis Reference Laboratory Muhimbili Tanzania

Background: Nontuberculous mycobacteria (NTM) usually comprise a group of environmental bacteria, with emerging but elusive coinfection with tuberculous mycobacteria, causing pulmonary tuberculosis. Whole genome sequencing may give insight into potential antimicrobial resistance genotypes, giving clinicians and policymakers proper directions in clinical applications and management regimens. Methods: WGS was performed on twenty-four gDNA isolates from archival samples at the Central Tuberculosis Reference Laboratory using the MinION Oxford Nanopore Sequencing approach. Out of twenty-four, two were confirmed to belong to the NTM group. Further analysis was done to resolve the complete genomes of two nontuberculous mycobacteria strains isolated from tuberculosis patients. We then combined phylogenomics, reference-based scaffolding and average nucleotide identity (ANI) analysis to delineate each strain's taxonomic position and corresponding features. Results: Our findings reveal that the two strains fit into the genus Mycolicibacterium, and the closest relative is Mycolicibacterium novocastrense. Coupling BacAnt and CARD-based antibiotic resistance analyses revealed multidrug-resistant genotypes of diverse spectra and mechanisms. While the BC02 strain is genetically resistant to beta-lactams, macrolides and rifamycins, the BC05 strain portrays an extended drug resistance genotype encompassing beta-lactams, macrolides, polyamines, and aminoglycosides. Both strains possess a single nucleotide polymorphism (SNP) of the RNA polymerase beta-subunit (rpoB), representing resistance to the first-line rifampicin. Additionally, the BC05 strain genetically portrays resistance to ethambutol, isoniazid and fosfomycin through mechanisms involving target alteration through SNPs, drug inactivation and efflux. Conclusion: Our findings strongly suggest the potential implication of multidrug-resistant NTM clinical isolates in the pathogenesis of pulmonary tuberculosis.

Risk factor of non-tuberculous Mycobacterium infection in patients with rheumatoid arthritis and other autoimmune diseases receiving biologic agents: A multicenter retrospective study

BackgroundEvidence regarding the association of the usage of biologic agents (Etanercept, Tocilizumab, adalimumab and so on), such as anti-tumor necrosis factor α, with the incidence and risk factors of non-tuberculous Mycobacteria (NTM) infection is limited. Therefore, this study aimed to investigate the incidence and risk factors of NTM and their associations with biologic agents’ usage, and also investigated the potential of Mycobacterium avium complex (MAC) antibodies as a predictor of NTM infection development. MethodsThis retrospective study included 672 patients with autoimmune diseases from four hospitals in Nagasaki, Japan, from January 1, 2011, to June 30, 2019, who fulfilled the inclusion criteria. ResultsOf the 672 patients, 9 (1.3%) developed complicated NTM infection, including two with disseminated infection, after the introduction of biologic agents. Of the nine patients, two died due to NTM infection but none tested positive for MAC antibodies prior to initiation of biologic agents. The mortality rate was higher in patients complicated with NTM than without NTM (22.2% vs 2.6%, P = 0.024). The corticosteroids dosage at the time of initiating the biologic agents was significantly higher in the NTM group than in the non-NTM group (median, 17 mg vs 3 mg, P = 0.0038). Conclusion: In the patients undergoing therapy with biologic agents, although NTM complication was rare, it could be fatal. In particular, for patients on a relatively high dose corticosteroids, careful observation is essential for identifying NTM complication, even if the MAC antibody test is negative.

Association of pulmonary nontuberculous mycobacteria with the outcomes of patients with lung cancer: A retrospective matched cohort study with a special emphasis on the impact of chemotherapy.

Nontuberculous mycobacteria (NTM) may be present in the respiratory tract of patients with lung cancer. We investigated the association of pulmonary NTM with the clinical features and outcomes of patients with lung cancer. Between 2015 and 2019, the data of patients diagnosed with lung cancer at a medical center in northern Taiwan were analyzed. Patients whose respiratory specimens were culture-positive for NTM were identified (NTM group). For each patient in the NTM group, a matched control was selected (control group). The survival of the two groups was compared using the Kaplan-Meier method and Cox proportional hazards regression analysis. Among 8718 patients with lung cancer, 5418 (62.1%) underwent a sputum mycobacterial culture. At least one NTM species was isolated from 138 (2.5%) patients. The median age was 72 years (range: 64-80). In the NTM group, 19.8% fulfilled both the microbiological and radiographic criteria for the diagnosis of NTM lung disease. Compared with the control group, the NTM group exhibited a lower body mass index (22.4 vs. 23.6, p=0.025) and a higher prevalence of structural lung disease (38.9% vs. 22.2%, p=0.004). The two-year survival was not significantly different between the two groups (hazard ratio [HR]: 1.110; 95% confidence interval [CI]: 0.702-1.754, p=0.656). In patients receiving chemotherapy, pulmonary NTM was associated with worse survival (HR: 2.497, 95% CI: 1.262-4.943, p=0.009). Except in patients receiving chemotherapy, pulmonary NTM may not be clinically relevant in patients with lung cancer.

Species diversity of microorganisms previously identified as nontuberculous mycobacteria by DNA hybridization.

Over the past 10 years, the clinical importance of opportunistic bacteria of the order Actinomycetales has increased significantly. While many problems for the Mycobacterium tuberculosis complex have been solved, for nontuberculous mycobacteria, some questions remain open. These pathogens have a number of structural features that allow them to persist in the external environment for a long time. The main inclusion criteria were cultural characteristics in assessing the growth of microorganisms on solid egg media. If nontuberculous mycobacteria (NTM) growth was detected, identification signs were carried out using the DNA hybridization method. Subsequently, these cultures were identified using the matrix-assisted laser desorption/ionization-time-of-flight (MALDI-ToF) mass spectrometry method. In case of obtaining unacceptable results of identification from primary inoculations, re-identification to obtain pure cultures was carried out after transferring the material from primary media to agar media: 5% blood agar and universal chromogenic medium. When re-identifying isolated cultures using MALDI-ToF mass spectrometry, all isolated cultures were analyzed, regardless of whether they belonged to the NTM group or not. DNA hybridization, which accounted for 59.5% of the total number of cultures included in the study, performed species identification of 188 strains. Using MALDI-ToF mass spectrometry, 345 strains were identified. The use of methods based on DNA hybridization makes it possible to identify quite accurately some of the most common NTM species. MALDI-ToF mass spectrometry is an important technique to allow species identification of most Actinomycetales. However, algorithms to standardize methods for their isolation from clinical material are needed.

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.

CT Imaging Characteristics of Nontuberculous Mycobacteria Lung Disease, Active Tuberculosis and Multi-Drug Resistant Tuberculosis.

The differential diagnosis of nontuberculous mycobacteria (NTM) lung disease, active tuberculosis (ATB) and multi-drug resistant tuberculosis (MDR-TB) remains difficult. To explore the CT imaging characteristics of NTM lung disease, ATB and MDR-TB for differential diagnosis. Patients with NTM lung disease (n=200), ATB (n=200) and MDR-TB (n=200) who were examined and treated from August 2013 to May 2021 were included. Their chest CT imaging results were retrospectively analyzed, and the imaging characteristics were compared. The proportion of cases complicated with underlying lung disease, cough and hemoptysis was significantly higher in NTM group than those in ATB and MDR-TB groups (P<0.05). Compared with ATB and MDR-TB groups, NTM group had significantly more cases of nodule-bronchus dilation type, but significantly fewer cases of nodule-mass type and other types (P<0.05). In NTM group, the cases of thin-wall cavity, bronchiectasis and centrilobular nodules increased, but the detection rate of thick-wall cavity, lung consolidation, atelectasis, lung damage, lung volume reduction, intrapulmonary calcification, hilar and mediastinal lymph node calcification, acinar nodules, pleural thickening and pleural effusion declined compared with ATB and MDR-TB groups (P<0.05). The detection rates of lesions, cavities and bronchiectasis in the lingual lobe of left lung and middle lobe of right lung were significantly higher in NTM group than those in ATB and MDR-TB groups (P<0.05). The imaging characteristics of NTM lung disease are quite similar to those of ATB and MDR-TB, but they can be differentially diagnosed through the types of cavities and nodules, incidence rate of bronchiectasis, and differences in lung consolidation, lung damage, calcification, pleural thickening and pleural effusion.

Mortality and Prognostic Factors of Nontuberculous Mycobacterial Infection in Korea: A Population-based Comparative Study.

Population-based studies on the mortality burden of nontuberculous mycobacteria (NTM) infection are lacking. We compared the long-term mortality of NTM-infected patients with tuberculosis (TB)-patients and the general population, and investigated mortality-associated factors. We analyzed nationwide-data from the Korean National Health Insurance and Korea-Statistical Office between 2002 and 2017. NTM infection was identified using the International Classification of Disease, Tenth Revision code, with one-to-one matching to TB patients and general population controls. A total of 530 401 individuals were analyzed, including 183 267 with NTM infections; 166 666 with TB; and 180 468 controls. The overall 6-, 10-, and 14-year cumulative survival probabilities in the NTM group were 86.3%, 80.8%, and 77.1%, respectively, which were significantly lower than those of the TB or control groups (log-rank P < .0001). In cases of NTM and TB coinfection, the overall 6-, 10-, and 14-year cumulative survival probabilities were 75.1%, 65.4%, and 57.0%, respectively. Multivariable analysis indicated that old age, male gender, province, and various respiratory or nonrespiratory comorbidities were significantly associated with mortality of NTM infection. The use of a macrolide (more than 1 year) negatively correlated with mortality of NTM infection (adjusted hazard ratio [aHR] 0.61, 95% confidence interval [CI] .53-.71), regardless of azithromycin (aHR 0.60, 95% CI .43-.85) or clarithromycin use (aHR 0.63, 95% CI .53-.75). NTM-infected patients had poor prognosis when compared to TB patients or the general population, especially for NTM and TB coinfection. NTM mortality was associated with certain demographic characteristics, but long-term use of macrolides may provide survival benefits.

Clinical characteristics of non-tuberculous mycobacterial pulmonary infections in Bamako, Mali.

The global spread of non-tuberculous mycobacteria (NTM) may be due to HIV/AIDS and other environmental factors. The symptoms of NTM and tuberculosis (TB) disease are indistinguishable, but their treatments are different. Lack of research on the epidemiology of NTM infections has led to underestimation of its prevalence within TB endemic countries. This study was designed to determine the prevalence and clinical characteristics of pulmonary NTM in Bamako. A cross-sectional study which include 439 suspected cases of pulmonary TB. From 2006 to 2013 a total of 332 (76%) were confirmed to have sputum culture positive for mycobacteria. The prevalence of NTM infection was 9.3% of our study population and 12.3% of culture positive patients. The seroprevalence of HIV in NTM group was 17.1%. Patients who weighed <55 kg and had TB symptoms other than cough were also significantly more likely to have disease due to NTM as compared to those with TB disease who were significantly more likely to have cough and weigh more than 55 kg (OR 0.05 (CI 0.02-0.13) and OR 0.32 (CI 0.11-0.93) respectively). NTM disease burden in Bamako was substantial and diagnostic algorithms for pulmonary disease in TB endemic countries should consider the impact of NTM.

Clinical aspects in patients with pulmonary infection caused by mycobacteria of the Mycobacterium abscessus complex, in the Brazilian Amazon.

ABSTRACTObjective:To describe the clinical manifestations of patients with pulmonary infection caused by mycobacteria of the Mycobacterium abscessus complex (MABSC), and to compare these manifestations with those of patients infected with other nontuberculous mycobacteria (NTM). Methods:This was a retrospective cohort study involving 43 patients divided into two groups: the MABSC group, consisting of patients with pulmonary infection caused by MABSC (n = 17); and the NTM group, consisting of patients with pulmonary infection caused by NTM other than MABSC (n = 26). Patients were previously treated with a regimen of rifampin, isoniazid, pyrazinamide, and ethambutol before the diagnosis of NTM was confirmed by two culture-positive sputum samples. The nucleotide sequences of the hsp65, 16S rRNA, and/or rpoB genes were analyzed to identify the mycobacteria. Data were collected on demographic, clinical, and radiological characteristics, as well as on treatment responses and outcomes. Results:Loss of appetite was the only clinical manifestation that was significantly more common in the MABSC group than in the NTM group (p = 0.0306). The chance of having to use a second treatment regimen was almost 12 times higher in the MABSC group than in the NTM group. Treatment success was significantly higher in the NTM group than in the MABSC group (83.2% vs. 17.6%; p < 0.0001). The chance of recurrence was approximately 37 times higher in the MABSC group than in the NTM group. Conclusions:In the study sample, treatment response of pulmonary disease caused by MABSC was less favorable than that of pulmonary disease caused by other NTM.

The risk factors for developing of chronic pulmonary aspergillosis in nontuberculous mycobacteria patients and clinical characteristics and outcomes in chronic pulmonary aspergillosis patients coinfected with nontuberculous mycobacteria.

Patients with chronic pulmonary aspergillosis (CPA) have a poor prognosis and CPA occurs in patients with various underlying diseases. Recently, the number of patients with CPA complicated by nontuberculous mycobacteria (NTM) has increased. Additionally, complications of both diseases have several problems like drug interactions. Since the impact of NTM on the outcome of CPA is not well understood, we investigated the risk factors for developing CPA and the clinical characteristics of CPA patients with or without NTM. We retrospectively investigated the medical records of NTM and CPA patients who were admitted to Nagasaki University Hospital between April 2008 and September 2013. Comorbid diseases, causative microorganisms, radiological findings, and outcomes were evaluated. During the study period, 82 and 41 patients were diagnosed as having NTM and CPA, respectively. Nine patients were coinfected with NTM and CPA, and cavitary type NTM and steroid usage were independent risk factors of development of CPA. Mortality rates in the coinfection group were significantly higher than those of the NTM without CPA group (P = .003, log-rank test). The rate of treatment initiation in the co-infection group (33.3%) was significantly lower than in the CPA without NTM group (84.4%) (P = .006). However, there were no significant differences in cumulative survival rate between both groups (P = .760, log-rank test). Cavity formation and steroid usage were the independent risk factors for NTM patients to develop CPA within long observation period, and development of CPA made outcomes poor. It is important to diagnose the development of CPA early and initiate treatment for CPA.

Chronic infection with non-tuberculous mycobacteria in patients with non-CF bronchiectasis: Comparison with other pathogens

IntroductionThe aim of this study is to compare characteristics of non-cystic fibrosis bronchiectasis (NCFBE) patients with chronic infections with non-tuberculous mycobacteria (NTM) versus those with Pseudomonas aeruginosa or other colonizations. MethodsThis was an observational, perspective study of consecutive NCFBE adult patients attending the outpatient bronchiectasis clinic at the San Gerardo Hospital in Monza, Italy, during 2012 and 2013. Patients with a chronic infection were included in the study and divided into three groups: those with NTM (Group A); those with P. aeruginosa (Group B); and those with other pathogens (Group C). Patients with both NTM and another pathogen were included in Group A. Comparison among the three study groups was performed using X2 or Fisher exact test for categorical variables or Kruskal–Wallis or Mann–Whitney test for continuous variables. ResultsA total of 146 patients (median age 67years, 40% males) were enrolled: 19 belonged to Group A, 34 to Group B and 93 to Group C. Within group A, 6 patients had only NTM isolation, 7 patients had NTM and P. aeruginosa co-infection and 6 patients had NTM plus another pathogen. The most common isolated pathogens among NTM was Mycobacterium avium complex (15 patients, 79%). A total of 4 patients (21%) with NTM were on active treatment. Patients affected by NTM pulmonary infection had a significantly less severe clinical, functional and radiological involvement compared with patients colonized by P. aeruginosa, see Table.Group A (NTM)n=19Group B (P. aeruginosa)n=34Group C (Others)n=93p Value∗p Value#p Value+Age (years), median (IQR)70 (64–75)74 (67–79)66 (53–72)0.0010.1720.050Male, n (%)8 (42)15 (44)36 (33)0.660––BMI, median (IQR)22 (19–26)24 (21–25)24 (21–27)0.352––BSI, median (IQR)5 (4–9)12 (8.5–16)5 (3–7)0.0010.0010.090Bhalla score, median (IQR)21 (15–34)36 (30.5–40.5)16 (10.5–21.5)0.0010.0160.076Idiopathic etiology, n (%)8 (42)11 (32)37 (40)0.721––Post-infective etiology, n (%)8 (42)16 (47)29 (31)0.244––Exacerbations/y, median (IQR)1 (0–2)2 (1.5–3.5)2 (1–2)0.0400.0240.132FEV1%, median (IQR)85 (59.75–109.5)58.5 (48.25–74)84 (62–102)0.0020.0100.857FVC%, median (IQR)94.5 (70–109.75)65 (56–81.5)88 (69.5–101.5)0.0030.0030.270∗Among the three groups: #Group A vs. Group B; +Group A vs. Group C; BMI: Body mass index; BSI: bronchiectasis severity index; y: year. ConclusionsColonization with P. aeruginosa seems to have the highest impact on the clinical, functional and radiological status of patients with NCFBE. No specific characteristics may help to identify NTM versus other pathogen colonizations. Thus, diagnostics for atypical mycobacteria should be performed on all patients with NCFBE, as suggested by recent international guidelines.

IMPACT OF COEXISTING NONTUBERCULOUS MYCOBACTERIA DURING THE TREATMENT OF PULMONARY TUBERCULOSIS

Nontuberculous mycobacteria (NTM) are often detected in patients undergoing treatment for pulmonary tuberculosis. This clinical status is thought to represent NTM disease, contamination, or colonization, but discriminating between these three conditions is difficult. We examined the clinical characteristics and pathogenicity of coexisting NTM among patients with pulmonary tuberculosis, as well as its impact on clinical practice. The subjects comprised 59 patients with pulmonary tuberculosis treated at the National Hospital Organization Utsunomiya National Hospital between January and December 2013. Patients in whom NTM was detected in one or more cultures were defined as the NTM group (19 patients), and they were compared to the non-NTM group (40 patients). Antiglycopeptidolipid (anti-GPL) core antibody titers were investigated in 18 patients from the NTM group. We observed no significant difference in patient characteristics (age, sex, complications, history of pulmonary tuberculosis, lung disease, chest imaging findings, degree of smear positivity on admission) between the two groups. Mean duration of hospitalization was markedly longer for the NTM group, excluding those with coexisting NTM after discharge (98.8 ± 7.9 days), than for the non-NTM group (58.3 ± 3.5 days; p < 0.001). No anti-GPL core antibodies were detected in any of the 18 patients from the NTM group, including 13 patients who fulfilled the ATS/IDSA criteria. Coexisting NTM observed during treatment for tuberculosis likely results from colonization or contamination and usually has low pathogenicity. However, this finding is related to prolonged hospitalization.

Recent advances on nontuberculous mycobacteria diseases in Asia

The isolation rate of nontuberculous mycobacteria (NTM) species and the prevalence of NTM-associated diseases are on the rise worldwide; however, the species distribution of NTM isolates and the types of diseases caused by NTM species vary from region to region. Treatment of a NTM disease is complicated, and there is no comprehensive guideline regarding the in vitro susceptibility of each antimicrobial agent against NTM. Therefore, appropriate anti-NTM treatment can only be recommended based on individual NTM species and local surveillance studies of anti-NTM resistance. Previous studies on the in vitro susceptibility of Mycobacterium avium complex (MAC) to clarithromycin in some Asian countries have revealed a low rate of resistance to that antimicrobial agent. Thus, a clarithromycin-based anti-MAC regimen should be effective for MAC infections. However, clarithromycin resistance due to the mutation of the 23S rRNA gene in MAC strains has been detected in many countries. Therefore, physicians should avoid monotherapy with clarithromycin and consider the possibility of clarithromycin resistance in patients who do not respond to clarithromycin-based regimens. Rifampicin is the critical component of successful management of Mycobacterium kansasii diseases. Although most M. kansasii isolates are susceptible to rifampicin in Western countries and in Japan, this agent may not work well in Taiwan. Rapidly growing mycobacteria (RGM) is a prevalent NTM group worldwide, particularly in Asia; however, each NTM species in this group may have its own distinct antibiotic susceptibility pattern, and close monitoring of the antibiotic-resistance patterns of RGM is necessary. Most important of all, the in vitro susceptibility may not represent the in vivo activity until the confirmation of the clinical study. Therefore, further investigation of the clinical effectiveness of the anti-NTM agents is warranted.

Different immunosuppressive mechanisms in multi-drug-resistant tuberculosis and non-tuberculous mycobacteria patients

Previous studies have demonstrated that cells from both multi-drug-resistant tuberculosis (MDR-TB) and non-tuberculous mycobacteria (NTM) patients respond poorly to mycobacterial antigens in vitro. In the present study, we compared the in vitro response of cells isolated from sensitive TB (NR-TB)-, MDR-TB- and NTM-infected patients. Analysis of T cell phenotype ex vivo revealed that both MDR-TB and NTM patients present an increased percentage of CD4(+) CD25(+-) forkhead box protein 3 (FoxP3)(+) and CD4(+) CD25(+) CD127(-) regulatory T (T(reg) ) cells when compared to NR-TB. Increased numbers of T(reg) cells and interleukin (IL)-10 serum levels were detected in MDR-TB, whereas elevated serum transforming growth factor (TGF)-β was found in the NTM group. Cells of MDR-TB patients stimulated with early secretory antigenic target (ESAT)-6, but not purified protein derivative (PPD), showed a lower frequency of CD4(+) /interferon (IFN)-γ(+) T cells and enhanced CD4(+) CD25(+) FoxP3(+) , CD4(+) CD25(+) CD127(-) and CD4(+) CD25(+) IL-10(+) T cell population. In addition, increased IL-10 secretion was observed in cultured MDR-TB cells following ESAT-6 stimulation, but not in NR-TB or NTM patients. In vitro blockade of IL-10 or IL-10Rα decreased the CD4(+) CD25(+) FoxP3(+) frequencies induced by ESAT-6 in MDR-TB, suggesting a role of IL-10 on impaired IFN-γ responses seen in MDR-TB. Depletion of CD4(+) CD25(+) T lymphocytes restored the capacity of MDR-TB T cells to respond to ESAT-6 in vitro, which suggests a potential role for T(reg) /T regulatory 1 cells in the pathogenesis of MDR-TB. Together, our results indicate that although the similarities in chronicity, NTM- and MDR-TB-impaired antigenic responses involve different mechanisms.

Nontuberculous mycobacteria in bronchiectasis: prevalence and patient characteristics

The aim of the current study was to investigate the prevalence and clinical associations of nontuberculous mycobacteria (NTM) in a well-characterised cohort of patients with adult-onset bronchiectasis. The sputum of all patients attending a tertiary referral bronchiectasis clinic between April 2002 and August 2003 was examined for mycobacteria as part of an extensive diagnostic work-up. NTM-positive patients subsequently had further sputa examined. A modified bronchiectasis scoring system was applied to all high-resolution computed tomography (HRCT) scans from NTM-positive patients, and a matched cohort without NTM. Out of 98 patients attending the clinic, 10 had NTM in their sputum on first culture; of those, eight provided multiple positive cultures. Three patients were treated for NTM infection. A higher proportion of NTM-positive than -negative patients were subsequently diagnosed with cystic fibrosis (two out of nine versus two out of 75). On HRCT scoring, more patients in the NTM-positive group had peripheral mucus plugging than in the NTM-negative group. In the current prospective study of a large cohort of patients with bronchiectasis, 10% cultured positive for nontuberculous mycobacteria in a random clinic sputum sample. Few clinical parameters were helpful in discriminating between groups, except for a higher prevalence of previously undiagnosed cystic fibrosis and of peripheral mucus plugging on high-resolution computed tomography in the nontuberculous mycobacteria group.

The prevalence and clinical significance of pulmonary infection due to non-tuberculous mycobacteria in Hong Kong

An unexpected increase in positive sputum cultures of non-tuberculous mycobacteria (NTM) was noted in Hong Kong in 1990 compared to previous years, in contrast to a steady decline in the number of positive cultures of Mycobacterium tuberculosis. A retrospective case note study was therefore undertaken to ascertain the clinical importance of the rise in NTM isolates. A representative sample of 183 of the 675 patients with NTM isolates from sputum during 1990 was identified. Cases were assigned to groups according to whether there was evidence of progressive pulmonary disease due to NTM (group 1), persisting colonization without evidence of progressive disease (group 2) or transient isolation of NTM without evidence of progressive disease (group 3). Of 168 cases with adequate clinical and radiological records, 28 (16·7%) represented progressive disease due to NTM and 6 (3·6%) represented persisting colonization. The remainder were both transient and clinically insignificant. Most patients (71%) with progressive pulmonary disease due to NTM had pre-existing lung damage, and 50% had received anti-tuberculous therapy for documented M. tuberculosis previously. The commonest organism involved was the M avium complex. Eighty-six percent of patients with progressive disease and 83% of those with persisting colonization had at least one smear positive sputum specimen, whereas only 2% of patients with sputum contamination had a smear positive sputum sample ( P<0·0001). M. malmoense, M. xenopi and M. fortuitum all appear to be rare causes of significant NTM disease in Hong Kong. However, M. chelonei caused four cases of progressive disease within the study population, two of which were fatal. Although positive sputum cultures of NTM are relatively common in Hong Kong, the majority do not appear to represent clinically significant infection. The spectrum of organisms identified differs from that reported in other regions of the world.