Clinical Significance of Nontuberculous Mycobacteria Isolated From Respiratory Specimens in a Chinese Tuberculosis Tertiary Care Center

An early and trustable indicator suggestive of non-tuberculosis mycobacteria isolation in a high tuberculosis burden setting

BACKGROUND

Distinguishing between nontuberculous mycobacterial (NTM) lung infections and pulmonary tuberculosis becomes challenging due to their similar clinical manifestations and radiological images. Consequently, instances of delayed diagnosis or misdiagnosis are highly frequent. A feasible and reliable indicator of the existence of NTM in the early stages of the disease would help to solve this dilemma.

METHODS

In this study, we evaluated the potential of smear-positive and Xpert assay (Cepheid, USA) negative outcomes as an early indicator of possible NTM infection in a high TB-burden setting retrospectively and prospectively.

RESULTS

During the study period, 12·77% (138/1081) of the smear-positive cases yielded negative outcomes with the simultaneous Xpert assay. From the 110 patients who yielded smear-positive/Xpert-negative outcomes and cultivated strain as well, 105 (95·45%) were proved to have NTM isolated. By incorporating an additional criterion of a negative result from the Interferon-gamma release assay, the accuracy of the screening method reached 100%. Regarding the NTM presence prediction value, smear-positive/Xpert-negative has a sensitivity of 24·86% (45/181) in all NTM isolated cases but 93·75-96·55% accuracy in retrospective study or 93·75% accuracy in prospective study in smear-positive NTM isolated cases. In addition, the specificity was ∼99·47% (943/948) in smear-positive tuberculosis cases.

CONCLUSION

The clue of the presence of NTM could be obtained on the first day of the hospital visit due to the point of care (POC) feature of smear testing and Xpert assay. About one-fourth of the NTM-isolated patients would benefit from this rapid, convenient, and reliable screening strategy in the given circumstance. Smear-positive/Xpert-negative outcome is an early, trustable indicator that is indicative of NTM isolation.

Global Epidemiology of Nontuberculous Mycobacterial Pulmonary Disease: A Review

Nontuberculous mycobacterial (NTM) isolation and pulmonary disease (NTM-PD) have continued to increase in most regions of the world, driven mainly by Mycobacterium avium. Single-center studies also support increasing trends as well as a persistent burden of undiagnosed NTM among persons suspected of having tuberculosis (TB), in countries with moderate-to-high TB prevalence. Cumulative exposure to water and soil presents an increased risk to susceptible hosts, and trace metals in water supply are recently recognized risk factors. Establishing standard case definitions for subnational and national surveillance systems with mandatory notification of NTM-PD are needed to allow comparisons within and across countries and regions.

T-SPOT with CT image analysis based on deep learning for early differential diagnosis of nontuberculous mycobacteria pulmonary disease and pulmonary tuberculosis

OBJECTIVES

This study aimed to establish a diagnostic algorithm combining T-SPOT with computed tomography image analysis based on deep learning (DL) for early differential diagnosis of nontuberculous mycobacteria pulmonary disease (NTM-PD) and pulmonary tuberculosis (PTB).

METHODS

A total of 1049 cases were enrolled, including 467 NTM-PD and 582 PTB cases. A total of 320 cases (160 NTM-PD and 160 PTB) were randomized as the testing set and were analyzed using T-SPOT combined with the DL model. The testing cases were first divided into T-SPOT-positive and -negative groups, and the DL model was then used to separate the cases into four subgroups further.

RESULTS

The precision was found to be 91.7% for the subgroup of T-SPOT-negative and DL classified as NTM-PD, and 89.8% for T-SPOT-positive and DL classified as PTB, which covered 66.9% of the total cases, compared with the accuracy rate of 80.3% of T-SPOT alone. In the other two remaining groups, where the T-SPOT prediction was inconsistent with the DL model, the accuracy was 73.0% and 52.2%, separately.

CONCLUSION

Our study shows that the new diagnostic system combining T-SPOT with DL based computed tomography image analysis can greatly improve the classification precision of NTM-PD and PTB when the two methods of prediction are consistent.

A glimpse into the genotype and clinical importance of non tuberculous mycobacteria among pulmonary tuberculosis patients: The case of Ethiopia

Laboratory identification of nontuberculous mycobacteria (NTM) species is not regularly performed while, they have a public health importance with a prevalence of more than 5% among pulmonary tuberculosis (PTB) patients in Ethiopia. Hence, this study aimed to identify the NTM species and their clinical significance among PTB patients. A retrospective study was conducted at the Ethiopian Public Health Institution’s (EPHI’s) national TB referral laboratory. Stored NTM isolates were genotyped using GenoType Mycobacterium CM/AS kit (Hain Life science, Germany). Data pertinent to the study was extracted from the EPHI’s database and patients’ medical records. Between January 2 & December 28 of 2017, a total of 3,834 samples were processed from 698 TB patients of whom 50% were female. Among 3,317 samples with mycobacterial culture results 7.3% were NTM and majority of them were identified from smear negative TB patients. M. simiae was the /predominant NTM among the genotyped isolates. All the studied NTM species were not clinically important however, considering the similarity of clinical and radiologic findings between NTM and MTBC infected patients, integrating NTM species identification in the routine TB laboratory diagnosis may augment clinicians’ decision particularly in DR-TB patients. Additional similar prospective study with a larger sample size is recommended. Moreover, urgent improvements on patients’ record keeping practice are required in the studied hospitals.

Identification and characterization of nontuberculous mycobacteria isolated from suspected pulmonary tuberculosis patients in eastern china from 2009 to 2019 using an identification array system

Objective

Nontuberculous mycobacteria (NTM) species are increasingly being isolated and have become a key factor affecting public health by causing pulmonary diseases. Most NTM species do not respond to conventional tuberculosis (TB) drugs. This study aimed to identify NTM isolated from suspected pulmonary TB patients from the Zhejiang province and analyze their distribution in the region.

Methods

A total of 1,113 NTM isolates from patients suspected to be suffering from acid-fast bacilli-positive tuberculosis were identified at the species level, using the CapitalBio Mycobacterium identification array and polymerase chain reaction amplification and sequencing of 16S-23S gene internal transcribed spacer (ITS), 16S rRNA, and hsp65.

Results

Of the 23,138 isolates, we identified 1,102 NTM (4.8%), mainly including Mycobacterium intracellulare (54.81%, 604/1,102), M. chelonae-M. abscessus (16.52%, 182/1,102), M. avium (13.16%, 145/1,102), M. kansasii (8.17%, 90/1,102), and M. gordonae (3.27%, 36/1,102).

Conclusion

The distribution of NTM species observed in patients with suspected pulmonary tuberculosis provides guidance for the diagnosis and treatment of NTM pulmonary diseases.

Disseminated Coinfection by Mycobacterium fortuitum and Talaromyces marneffei in a Non-HIV Case

Background

Mycobacterium fortuitum is a rapidly growing non-tuberculous mycobacterium (NTM) with weak pathogenicity. Here, we present a rare case of disseminated M. fortuitum and Talaromyces marneffei coinfection in a human immunodeficiency virus (HIV) negative patient.

Case Presentation

A 28-year-old female was admitted to our hospital due to 2 months of swelling of lymph nodes on the right side of her cervix, accompanied by repeated low fever for more than 1 month. Biopsy of the right cervical lymph node and endobronchial ultrasound-guided transbronchial fine needle aspiration (EBUS-TBNA) both suggested granulomatous inflammation. The bacterial culture and mycobacteria examination of the lesion as well as HIV antibody test were all negative. Disseminated T. marneffei infection was diagnosed by the quantitative polymerase chain reaction (qPCR) results from the blood showing 1798 copies/ul. In the meantime, treatment with amphotericin B combined with cefoxitin was administered for suspected NTM infection. However, the once-dropped fever recurred and the lymph nodes continued to swell. Metagenomics next-generation sequencing (mNGS) detection of the lymph nodes indicated M. fortuitum. After combination treatment with amphotericin B, voriconazole, linazolamide, and imipenem, the patient's body temperature returned to normal, the lymph node swelling was gradually reduced, and the lung lesion was absorbed.

Conclusion

We report the first case of an HIV-negative patient diagnosed with disseminated M. fortuitum and T. marneffei coinfection with nonspecific clinical manifestation, in order to heighten awareness of these infections.

Challenges in the management of slowly growing non-tuberculous mycobacteria causing pulmonary disease: Perspectives from a high burden country

PURPOSE

There is a dearth of data on epidemiology, diagnosis and management of slow growing non tuberculous mycobacteria(NTM) in India, despite being a TB endemic country. This study aims to describe the geographic distribution, risk factors, and the challenges in management of slow growing NTM causing pulmonary infections.

METHODS

Over a period of 3 years, all slow growing NTM received from pulmonary specimens at a tertiary care centre were further studied from electronic hospital records to correlate non tuberculous mycobacteria species with demographics, geographic location, describe comorbidities including immunosuppression, radiologic findings and treatment regimes.

RESULTS

M.intracellullare was found in the majority of isolates with significant geographic variation and M.simiae the second commonest found exclusively in southern states. Common comorbidities included a previous history of treatment for tuberculosis, structural lung disease as well as systemic risk factors. Disseminated disease only occurred in immunocompromised hosts as was expected, but at a high rate of 44%. Treatment completion and outcomes were difficult to attain in our population.

CONCLUSION

The burden of NTM infection and its management in India remain a challenge. Ensuring it is made a notifiable disease may improve the current situation.

Non-tuberculous mycobacteria immunopathogenesis: Closer than they appear. a prime of innate immunity trade-off and NTM ways into virulence

Introduction

The growing incidence of non‐tuberculous mycobacteria (NTM) and changes in epidemiological factors have indicated that immune dysregulation may be associated with the emergence of NTM. Minireview entails to acknowledge complex interaction and new ways NTM are evolving around diverse immune status.

Methods

In order to perform this review, we selected peer reviewed, NLM database articles under the terms NTM, mycobacterium complex ‘AND’ ‐Host‐ immune response, immunity regulation, Disease, Single Nucleotide Polymorphism (SNP´s), and ‐pathogen‐ followed by a snow ball rolling basis search on immune components and NTM related with diseases distribution.

Results

The universal exposure and diversity of NTM are well‐documented; however, hospitals seldom establish vigilant control of water quality or immunodeficiencies for patients with NTM infections. Depending on the chemical structures and immune mechanisms presented by various NTM varieties, they can trigger different effects in dendritic and natural killer cells, which release interleukin (IL)‐17, tumour necrosis factor‐α (TNF‐α), interferon‐γ (IFN‐γ) and rIL‐1B. The T helper (Th)2‐acquired immune response is responsible for autoimmune responses in patients with NTM infections, and, quite disturbingly, immunocompetent patients have been reported to suffer from NTM infections.

Conclusion

New technologies and a comprehensive view has taught us; to acknowledge metabolic/immune determinants and trade‐offs along transit through mutualism‐parasite continuous.

Prevalence of Nontuberculous Mycobacterial Disease in the Changchun District of China

Rates of nontuberculous mycobacterial (NTM) disease are rapidly increasing throughout the globe. NTM disease, as an emerging infectious disease, it is very important to summarize and analyze the prevalence and main pathogenic bacteria. However, there is no relevant report in Changchun district. In the present report, 8765 clinical samples were collected between January 2017 and December 2019, we reviewed patient electronic medical records and thereby summarized the causative species associated with NTM disease in the Changchun district of China. Of 8765 clinical samples, 1987 samples yielded positive cultures. Of these cultures, 1868 (94.01%) were Mycobacterium tuberculosis, 37 (1.86%) were Mycobacterium bovis, and 82 (4.13%) were NTM. A total of 84 NTM strains were isolated from these 82 cultures, with Mycobacterium intracellulare being the most prevalent isolate therein (44.05%). NTM infection status was associated with location of residence [OR (95% CI) 3.92 (1.20-12.8)]. No apparent correlations were observed between cultured NTM species and patient clinical symptoms. Bronchiectasis was the most prevalent radiographic finding associated with NTM cases [OR (95% CI) 9.00 (1.27-63.89)]. In summary, NTM disease is a growing threat to global public health, and researchers and clinicians should thus focus on the appropriate identification of NTM species and the differentiation between NTM infections and tuberculosis.

Synthesis and activity of BNF15 against drug-resistant Mycobacterium tuberculosis

Aim: Tuberculosis is the leading cause of mortality among infectious diseases worldwide. Finding a new competent anti tubercular therapy is essential. Materials & methods: We screened thousands of compounds and evaluated their efficacy against Mycobacterium tuberculosis. Results: Initially, 2-nitronaphtho[2,3-b]benzofuran-6,11-dione was active against M. tuberculosis. Next, among 15 newly synthesized derivatives, BNF15 showed promising effect against all drug-sensitive and drug-resistant M. tuberculosis (MIC: 0.02-0.78 μg/ml). BNF15 effectively killed intracellular M. tuberculosis and nontuberculous mycobacteria. BNF15 exhibited a prolonged post antibiotic effect superior to isoniazid, streptomycin, and ethambutol and synergistic interaction with rifampicin. In acute oral toxicity test, BNF15 did not show toxic effect at a concentration up to 2000 mg/kg. Conclusion: These results highlight the perspective of BNF15 to treat drug-resistant M. tuberculosis.

Treatment of pulmonary disease caused by Mycobacterium kansasii

As a cause of lung disease (LD), Mycobacterium kansasii is regarded as a highly virulent species among nontuberculous mycobacteria (NTM). Both the frequency of M. kansasii isolates and global prevalence of M. kansasii-LD have increased gradually over recent decades. Treatment of M. kansasii-LD is recommended because of the disease's poor prognosis and fatal outcome. The decision on the optimal time point for treatment initiation should be based on both the benefits and risks posed by multiple antimicrobial agents. For treatment-naïve patients with M. kansasii-LD, rifampin-containing multiple antimicrobial regimens for ≥12 months after culture negative conversion are effective. However, some challenges remain, such as determining the precise length of treatment duration as well as addressing intolerable adverse effects, the uncertain effectiveness of isoniazid and ethambutol in treatment, the uncertain correlation between in vitro drug susceptibility testing and clinical outcomes, and the increasing prevalence of clarithromycin-resistant M. kansasii isolates. Short-course and effective therapies must be developed. New candidate drugs, such as tedizoid and clofazimine, exhibit excellent antimycobacterial activity against M. kansasii in vitro, but in vivo studies of their clinical applications are lacking. This paper reviews the treatment, outcomes and future directions in patients with M. kansasii-LD.

Nontuberculous mycobacterial lung disease epidemiology in Taiwan: A systematic review

Nontuberculous mycobacteria (NTM) are critical emerging global infectious pathogens. Though NTM can be mere colonizers when isolated from human specimens, NTM are also responsible for diverse human infections. NTM-lung disease (NTM-LD) is the most common human disease entity. The present review aims to provide general insight into NTM-LD epidemiology in Taiwan. In reviewing NTM epidemiology in Taiwan, we discovered three distinguishing features. First, NTM disease incidence has increased in Taiwan over the past decade. Second, the distribution of NTM varies geographically in Taiwan. Mycobacterium avium-intracellulare complex (MAC) is the dominant species in northern Taiwan, whereas Mycobacterium abscessus complex and MAC may be equally dominant in southern Taiwan. Third, researchers in Taiwan have published valuable research investigating NTM among special patient populations, including patients in intensive care units, with ventilator dependency, with pulmonary tuberculosis, and who are infected with specific NTM species. The largest obstacle to clarifying NTM epidemiology in Taiwan may be the lack of routine NTM species identification in laboratories. Increased awareness of NTM diseases and acknowledgment that NTM species identification is crucial and guides clinical management are essential steps for facilitating the identification of NTM species in laboratories.

An Intensified Regimen Containing Linezolid Could Improve Treatment Response in Mycobacterium abscessus Lung Disease

Background

Treatment response for the Mycobacterium abscessus (M. abscessus) lung disease remains far from satisfying. An effective regimen is needed to solve the problem.

Methods

We retrospectively reviewed the medical records of all patients with M. abscessus lung disease who received antibiotics regimen at Beijing Chest Hospital Affiliated to Capital Medical University between July 1, 2010, and February 1, 2018. Patients were administered a conventional antibiotics regimen (including macrolide and moxifloxacin, along with an initial 12-week course of low-dose cefoxitin and amikacin) or intensified regimen (including a higher dosage of cefoxitin and linezolid besides conventional drugs), respectively. The time to sputum-culture conversion and proportion of sputum-culture conversion in liquid broth were investigated to evaluate the efficacy and evaluation of safety by performing the classification of adverse events according to the Division of AIDS, National Institute of Allergy and Infectious Disease. Patients were followed for 18 months from baseline.

Results

In the conventional regimen group, the sputum conversion rate at 18 months was 29.4% (10/34), and the median time until sputum conversion was 2 months (IQR, 1-2 mo). Furthermore, in the intensified regimen group, the sputum conversion rate was 81.3% (13/16), and the median time until sputum conversion was 1 month (IQR, 1-1 mo). Leukopenia and drug-induced hepatotoxicity occurred more frequently in the intensified regimen group in contrast with the conventional regimen group patients. However, only 1 adverse event in the intensified regimen group was classified as severe adverse event.

Conclusions

The intensified regimen could improve sputum conversion of M. abscessus lung disease compared with conventional regimen, but close safety surveillance is necessary to monitor adverse events.

Characterization of non-tuberculous mycobacterial pulmonary disease in Nanjing district of China

BACKGROUND

Environmental bacteria, nontuberculous mycobacteria (NTM), are recognized as one of the major human infection pathogens. NTM are prone to be mistaken as multidrug-resistant Mycobacterium tuberculosis and challenge our fight against TB. In addition, treatment of NTM per se is intractable. Remarkably, the distribution of NTM pathogenic species is geographically specific. Thus, it is very important to summarize the prevalent features and clinical symptoms of NTM pulmonary disease. However, In Nanjing district, southeast China, there is no such a report.

METHODS

Through investigating electronic medical records and analyzing data of clinical examination system (Lis), we retrospectively summarized the NTM species from 6012 clinical isolates from May 2017 to August 2018, and analyzed the association between NTM species and clinical symptoms.

RESULTS

Of 6012 clinical specimens, 1461 (24.3%) could grow in the MGIT 960 broth. Among these positive isolates, 1213 (83%) were M. tuberculosis, 22 (1.5%) were M. bovis, and 226 (15.5%) were NTM. After deducting redundancy, those NTM specimens were confirmed from 154 patients, among which, 87 (56.5%) patients met the full ATS/IDSA NTM disease criteria. The most common etiologic agent was M. intracellulare (70.1%). NTM infection was associated with age, based on which 68.6% male patients and 77.8% female patients were over 50 years old. The older patients were more likely to have hemoptysis, but the younger patients were more likely to manifest chest congestion. Male patients were more likely to have shortness of breath and females were more likely to have hemoptysis. The most common radiographic presentation of NTM pulmonary disease was bronchiectasis, accounting for 39.1%. Remarkably, multiple and thin-walled cavities were outstanding. The most frequent comorbidity of NTM disease was previous tuberculosis (64%), followed by clinical bronchiectasis (19.5%), HIV (19.5%), and 6.9% chronic obstructive pulmonary disease (COPD). There was no association between NTM species and clinical symptoms.

CONCLUSION

This study retrospectively investigated the prevalence of NTM pulmonary disease in Nanjing district, southeast China. Similar to Beijing area, north China, M. intracellulare was the major pathogenic NTM species. Clinical symptoms of the disease were not species-specific. Previous TB and HIV infection immensely enhanced risk of NTM disease.

Evaluating the clinical significance of nontuberculous mycobacteria isolated from respiratory samples in Iran: an often overlooked disease

Purpose

Nontuberculous mycobacteria (NTM) infection is an increasing problem worldwide whose clinical significance is still largely unknown. The aim of this study was to investigate the epidemiology of NTM infection from respiratory samples and to determine their clinical significance.

Patients and methods

This cross-sectional study was performed on 7,825 clinical samples from December 2015 to December 2017. Detection was conducted using phenotypic and genotypic (hsp65 PCR-RFLP, rpoB, and 16S rRNA genes sequencing) methods. All clinical information including symptoms and radiological findings was extracted from patients’ records.

Results

A total of 478 were confirmed to have respiratory samples which were culture positive for mycobacteria, with the prevalence of NTM infection obtained as 53 (11.1%). Overall, Mycobacterium (M.) fortuitum was the most frequent NTM isolate, followed by M. simiae, M. kansasii, M. gordonae, and M. conceptionense. There was a relationship between NTM isolates and gender (P=0.039), symptoms (P=0.048), and radiographic findings (P=0.013). Bronchiectasis, infiltration, and cavitary lesion were the most frequent radiological findings in M. fortuitum, M. simiae, and M. kansasii, respectively, with cough being the most frequent symptom.

Conclusion

We reported five different NTM isolates in respiratory samples with a high frequency of M. fortuitum. NTM infections may play an important role in causing pulmonary disease and in tuberculosis management in endemic settings. Nevertheless, more studies are required to further examine the clinical significance of NTM isolates.

Clinical relevance of non-tuberculous mycobacteria isolated from respiratory specimens: seven year experience in a UK hospital

The frequency of isolation of non-tuberculous mycobacteria (NTM) species from respiratory specimens is increasing, however the clinical relevance of such identifications vary by mycobacterial species and geographical location. A retrospective study of 853 NTM isolates from respiratory samples from 386 patients over seven years was performed. Clinical records and radiographic information were examined. Clinical significance was assessed by American Thoracic Society diagnostic criteria. 25% of all patients with respiratory isolates met criteria for non-tuberculous mycobacterial pulmonary disease (NTM-PD). Significant symptoms were weight loss, fever, night sweats, productive cough and haemoptysis. HIV co-infection was a significant risk factor for disease. Cavities, nodules and tree-in-bud were significant radiographic findings. Mycobacterium avium complex (MAC) were the dominant species isolated from this patient cohort. Mycobacterium abscessus (M. abscessus) was the species most likely to cause clinically significant disease and be sputum smear positive, thus warranting particular attention.

Diversity of Nontuberculous Mycobacteria in Kuwait: Rapid Identification and Differentiation of Mycobacterium Species by Multiplex PCR, INNO-LiPA Mycobacteria v2 Assay and PCR Sequencing of rDNA

OBJECTIVE

Nontuberculous mycobacteria (NTM) often cause disease that is clinically indistinguishable from tuberculosis. Specific identification is important as treatment varies according to Mycobacterium species causing the infection. This study used multiplex PCR (mPCR) assay for rapid differentiation of mycobacterial growth indicator tube 960 system (MGIT) cultures as Mycobacterium tuberculosis (MTB) or NTM together with INNO LiPA Mycobacteria v2 assay (LiPA) and/or PCR sequencing of rDNA for species-specific identification of selected MTB and all NTM isolates in Kuwait.

MATERIALS AND METHODS

DNA was extracted from MGIT cultures (n = 1,033) grown from 664 pulmonary and 369 extrapulmonary specimens from 1,033 suspected tuberculosis patients. mPCR was performed to differentiate MTB from NTM. LiPA was performed and results were interpreted according to kit instructions. rDNA was amplified and sequenced by using panmycobacterial primers.

RESULTS

mPCR identified 979 isolates as MTB, 53 as NTM and 1 isolate as mixed culture. LiPA and/or PCR sequencing confirmed 112 of 979 selected isolates as MTB. Mixed culture contained M. tuberculosis and M. fortuitum. LiPA yielded 12 patterns and identified 10 species/species complexes among 47 NTM, M. kansasii + M. scrofulaceum in one culture and 5 isolates only at genus level. PCR sequencing yielded more specific identification for 22 isolates at the species/subspecies level.

CONCLUSIONS

mPCR rapidly differentiated MTB from NTM. LiPA identified 44 of 52 NTM isolates at the species/species complex level and 2 mixed cultures. PCR sequencing yielded more specific identification at the species/subspecies level. Rapid differentiation as MTB or NTM by mPCR, followed by species-specific NTM identification by LiPA/PCR sequencing is suitable for the proper management of mycobacterial infections in Kuwait.

Effect of Cetylpyridinium Chloride (CPC) on Colony Formation of Common Nontuberculous Mycobacteria

Cetylpyridinium chloride (CPC) is widely used to decontaminate water samples for the cultivation of nontuberculous mycobacteria (NTM). The rationale for using CPC is that it kills more non mycobacteria than NTM and thereby prevents the outgrowth and detection of mycobacterial colonies on solid media. The few CPC-susceptibility measurements that have been published, suggest that CPC-decontamination does kill significant numbers of NTM. We confirm that observation here and further demonstrate that CPC-susceptibility varied significantly by one log between representative NTM species and between strains of the same species. CPC-susceptibility was the same for cells collected from cultures or water-acclimated (P = 0.6485, T-test) and CPC-susceptibility was relatively similar over the range of commonly employed CPC dosages. We conclude that use of CPC as decontaminating agent may lead to failure to recover an NTM isolate and considerable underestimates of NTM numbers.

High rates of Mycobacterium fortuitum isolation in respiratory samples from Iranian patients with suspected tuberculosis: is it clinically important?

PURPOSE

Although Mycobacterium fortuitum (M. fortuitum) is not an organism rarely isolated from respiratory samples, its clinical importance is still not fully understood, which therefore prompted our current study.

METHODOLOGY

We evaluated respiratory samples from 6800 patients with suspected tuberculosis from May 2014 to May 2016, for the detection of M. fortuitum using phenotypic and genotyping methods.Results/Key findings. Of the 40 patients with M. fortuitum lung disease, 35 had two or more positive culture results. The mean age of these 35 patients was 50.7±18.4 years, and 20 (57.1 %) were men. Sputum (68.6 %), haemoptysis (51.4 %), cough (45.7 %) and gastroesophageal disease (22.9 %) were the major presenting symptoms. Cystic fibrosis, other bacterial lung diseases and lung cancer were the main underlying pulmonary diseases. Five patients (12.5 %) were human immunodeficiency virus (HIV) positive. The most common chest X-ray findings were reticulonodular opacities (53.3 %). Multivariate logistic regression analysis revealed that cigarette smoking history (OR 0.334, 95 % CI 0.125-0.843, P=0.048) and underlying lung disease (OR 0.393, 95 % CI 0.216-0.588, P=0.023) were significant predictors for positive M. fortuitum infection.

CONCLUSION

These results demonstrated the high frequency of M. fortuitum in respiratory samples and that this bacterium causes transient infection or colonization in patients with underlying pulmonary conditions, such as cystic fibrosis and cigarette smoking-induced. Additionally, it appears that infection with M. fortuitum is particularly common and may be important in patients with HIV.

High rates of nontuberculous mycobacteria isolation from patients with presumptive tuberculosis in Iran

Nontuberculous mycobacteria (NTM) can cause disease which can be indistinguishable from tuberculosis (TB), posing a diagnostic and therapeutic challenge, particularly in low- and middle-income settings. We aimed to investigate the mycobacterial agents associated with presumptive clinical pulmonary TB in Iran. A total of 410 mycobacterial isolates, obtained between March 2014 and January 2016, from 7600 clinical samples taken from consecutive cases of presumptive diagnosis of TB were identified. Phenotypic and molecular tests were used to identify the isolated organisms to the species level. Single-locus and multilocus sequence analysis based on 16S rRNA, rpoB, hsp65 and ITS locus were used to confirm the results. Of 410 consecutive strains isolated from suspected TB subjects, 62 isolates (15.1%) were identified as NTM. Patients with positive NTM cultures met American Thoracic Society diagnostic criteria for NTM disease. Mycobacterium simiae was the most frequently encountered (38.7%), followed by Mycobacterium fortuitum (19.3%), M. kansasii (17.7%) and M. avium complex (8.0%). Isolation of NTM, including M. simiae, from suspected TB cases is a serious public health problem and merits further attention by health authorities, physicians and microbiologists.