Simultaneous detection of Mycobacterium tuberculosis complex and nontuberculous mycobacteria in respiratory specimens

Diagnostic Criteria and the Decision to Treat Nontuberculous Mycobacterial Pulmonary Disease

The diagnosis of nontuberculous mycobacterial (NTM) pulmonary disease is based on three criteria: patient's symptoms, radiographic findings, and microbiologic results. The microbiologic criterion is the most complicated because it requires more than one positive sputum acid-fast bacilli culture. Clinicians are challenged to apply the diagnostic criteria in the context of variable patient symptoms, NTM pathogenicity, and host susceptibility. The decision to treat NTM pulmonary disease entails assessment of the risks and benefits of therapy and the patient's wishes and ability to receive treatment.

Mixed infection of three nontuberculous mycobacteria species identified by metagenomic next-generation sequencing in a patient with peritoneal dialysis-associated peritonitis: a rare case report and literature review

BACKGROUND

Peritonitis caused by nontuberculous mycobacteria (NTM) is an infrequent but important complication in patients undergoing peritoneal dialysis (PD). There has been no report of mixed infections with multiple NTM. Peritoneal dialysis-associated peritonitis (PDAP) caused by Mycobacterium abscessus is more common than that caused by M. smegmatis and M. goodii.

CASE PRESENTATION

This case concerns a patient with PDAP caused by gram-positive bacilli, which could not be identified at the species level in successive detections of initial peritoneal effluent. Later, M. smegmatis was detected with no sensitivity results in bacterial culture. However, metagenomic next-generation sequencing (mNGS) and first whole-genome sequences indicated that there were three species coexisting in the culture, including M. smegmatis (24,708 reads), M. abscessus (9224 reads), and M. goodii (8305 reads). This is the first case of PDAP with specific evidence that conventional detection methods isolated a poorly pathogenic NTM, whereas mNGS and first whole-genome sequences identified multiple NTM. Pathogenic bacteria might not be detected using conventional methods due to their lower abundance. This case report is the first description of mixed infections with more than two species of NTM during PDAP.

CONCLUSIONS

PDAP caused by multiple NTM is rare, and the diagnosis is difficult. When NTM are isolated by conventional tests in patients who are suspected of infection, clinicians should be vigilant, and further tests should be performed to determine the presence of rare or even previously unknown bacteria, for which the quantity is relatively low, but the pathogenicity is high. The rare pathogen may be a primary agent in causing such complications.

Performance assessment of SD Bioline TB MPT64 assay for the diagnosis of Mycobacterium tuberculosis complex in Lagos, Nigeria

This study assessed the performance of SD Bioline MPT64 immunochromatographic test for the identification of Mycobacterium tuberculosis complex (MTBC) in Nigeria.A total of 157 mycobacterial isolates, comprising 120 (76.4%) MTBC (M. tuberculosis, 112; M. africanum, 5; M. bovis, 3) and 37 (23.6%) non-tuberculous mycobacteria (NTM) isolates from patients attending six DOTS centers in Lagos between June 2012 and July 2014 were analyzed. All the isolates were grown on Bactec MGIT960 liquid media and identified in parallel by the conventional method and MPT64 immunochromatographic test. Discrepant results were resolved using the line probe assay.The comorbid disease rates for HIV and type 2 diabetes were 20.9% and 8.2%, respectively. Compared to the conventional method, SD Bioline MPT64 identified 117 MTBC isolates correctly, producing a sensitivity of 97.5% (95% CI, 92.9-99.2) at a shorter growing median time of 11 days compared to 26 days by the conventional method. The three undetected MTBC were confirmed by the line probe assay to be M. tuberculosis strains. The test also identified all the NTM correctly producing a specificity of 100% (95% CI, 90.7-100).This study supports the integration of SD Bioline TB MPT64 antigen test into diagnostic workflow for rapid MTBC case identification in Nigeria.

A Novel Method That Allows SNP Discrimination with 160:1 Ratio for Biosensors Based on DNA-DNA Hybridization

Highly sensitive (high SBR) and highly specific (high SNP discrimination ratio) DNA hybridization is essential for a biosensor with clinical application. Herein, we propose a method that allows detecting multiple pathogens on a single platform with the SNP discrimination ratios over 160:1 in the dynamic range of 10¹ to 10⁴ copies per test. The newly developed SWAT method allows achieving highly sensitive and highly specific DNA hybridizations. The detection and discrimination of the MTB and NTM strain in the clinical samples with the SBR and SNP discrimination ratios higher than 160:1 indicate the high clinical applicability of the SWAT.

Whole-Genome Sequencing Analysis to Identify Infection with Multiple Species of Nontuberculous Mycobacteria

Mixed infection with multiple species of nontuberculous mycobacteria (NTM) is difficult to identify and to treat. Current conventional molecular-based methods for identifying mixed infections are limited due to low specificity. Here, we evaluated the utility of whole-genome sequencing (WGS) analysis to detect and identify mixed NTM infections. Analytical tools used included PubMLST, MetaPhlAn3, Kraken2, Mykrobe-Predictor and analysis of heterozygous SNP frequencies. The ability of each to identify mixed infections of NTM species was compared. Sensitivity was tested using 101 samples (sequence sets) including 100 in-silico simulated mixed samples with various proportions of known NTM species and one sample of known mixed NTM species from a public database. Single-species NTM control samples (155 WGS samples from public databases and 15 samples from simulated reads) were tested for specificity. Kraken2 exhibited 100% sensitivity and 98.23% specificity for detection and identification of mixed NTM species with accurate estimation of relative abundance of each species in the mixture. PubMLST (99% and 96.47%) and MetaPhlAn3 (95.04% and 83.52%) had slightly lower sensitivity and specificity. Mykrobe-Predictor had the lowest sensitivity (57.42%). Analysis of read frequencies supporting single nucleotide polymorphisms (SNPs) could not detect mixed NTM samples. Clinical NTM samples (n = 16), suspected on the basis of a 16S-23S rRNA gene sequence-based line-probe assay (LPA) to contain more than one NTM species, were investigated using WGS-analysis tools. This identified only a small proportion (37.5%, 6/16 samples) of the samples as mixed infections and exhibited only partial agreement with LPA results. LPAs seem to be inadequate for detecting mixed NTM species infection. This study demonstrated that WGS-analysis tools can be used for diagnosis of mixed infections with different species of NTM.

Clinical Relevance and Characteristics of Nontuberculous Mycobacterial Pleuritis

Nontuberculous mycobacteria (NTM) disease is of increasing public health concern; however, data regarding pleural effusion in NTM disease patients are limited. The purpose of this study was to investigate the clinical relevance and characteristics of NTM pleuritis. Patients with pleural effusion and NTM disease diagnosed between April 2012 and November 2017 were enrolled and their medical records were retrospectively reviewed. Clinical characteristics and treatment outcomes were analyzed. A total of seven among 100 patients with NTM disease had NTM pleuritis (7%). Flow cytometry of T and B lymphocytes revealed varying degrees of cellular immunodeficiency in five cases (71.4%). NTM pleuritis with pneumothorax occurred in five patients (71.4%) and bronchopleural fistula (BPF) was also found in four of them. All seven patients had delayed diagnosis and the mean time of diagnosis was 7 months (1-24 months). Four patients successfully completed treatment, while three patients (42.8%) succumbed to progressing NTM disease. Low CD4-positive T-cell counts were common in NTM pleuritis patients. Delayed diagnosis and treatment resulted in increased incidence of NTM pleurisy and poor prognosis. Moreover, BPF is perhaps a characteristic feature of Mycobacterium avium complex-associated pleuritis.

Examining the Complex Relationship Between Tuberculosis and Other Infectious Diseases in Children

Millions of children are exposed to tuberculosis (TB) each year, many of which become infected with Mycobacterium tuberculosis. Most children can immunologically contain or eradicate the organism without pathology developing. However, in a minority, the organism overcomes the immunological constraints, proliferates and causes TB disease. Each year a million children develop TB disease, with a quarter dying. While it is known that young children and those with immunodeficiencies are at increased risk of progression from TB infection to TB disease, our understanding of risk factors for this transition is limited. The most immunologically disruptive process that can happen during childhood is infection with another pathogen and yet the impact of co-infections on TB risk is poorly investigated. Many diseases have overlapping geographical distributions to TB and affect similar patient populations. It is therefore likely that infection with viruses, bacteria, fungi and protozoa may impact on the risk of developing TB disease following exposure and infection, although disentangling correlation and causation is challenging. As vaccinations also disrupt immunological pathways, these may also impact on TB risk. In this article we describe the pediatric immune response to M. tuberculosis and then review the existing evidence of the impact of co-infection with other pathogens, as well as vaccination, on the host response to M. tuberculosis. We focus on the impact of other organisms on the risk of TB disease in children, in particularly evaluating if co-infections drive host immune responses in an age-dependent way. We finally propose priorities for future research in this field. An improved understanding of the impact of co-infections on TB could assist in TB control strategies, vaccine development (for TB vaccines or vaccines for other organisms), TB treatment approaches and TB diagnostics.

[The informative value of various methods for identifying acid-fast bacilli in relation to the degree of tuberculosis process activity]

Carbol fuchsin (Ziehl-Neelsen) staining is a major method used since the late nineteenth century to detect Mycobacterium tuberculosis in the tissues. At the same time, the number of mycobacteria does not frequently show a clinical and morphological correspondence to the activity of the infectious process.

OBJECTIVE

To reveal the morphological characteristics of Mycobacterium tuberculosis in patients with long-lasting tuberculosis.

MATERIAL AND METHODS

Twenty-four autopsies of verified fibrous-cavernous tuberculosis were examined. Paraffin sections were stained with hematoxylin and eosin, carbol fuchsin (Ziehl-Neelsen), or auramine-rhodamine (followed by luminescence microscopic examination); an immunohistochemical (IHC) study with serum to PAV (Protein antigen B) was conducted.

RESULTS AND DISCUSSION

The changes characteristic of progressive tuberculosis were revealed in all the cases. The Ziehl-Neelsen staining revealed isolated clusters of acid-fast bacilli (a total of 1,000 in less than 10 fields of view). When stained with auramine-rhodamine, the number of found mycobacteria proved to be significantly larger (a total of 1,000 to 10,000 in 10-50 fields of view) and that was greatest in the IHC study (a total of over 10,000 in more than 50 fields of view). At the same type, all types of studies revealed that the localization of mycobacteria was exclusively extracellular. The Ziehl-Neelsen staining indicated that the proportion of typical bacilli was much higher (85-95%; mean 88.13±2.14) than that (50-85%; mean 64.38±4.24%) identified when stained with auramine-rhodamine and even more significantly more than that (50-70%; mean 57.29±2.78%) detected during the IHC study. The indicators were equally different for the atypical morphological forms of mycobacteria identified in minimal quantities by the Ziehl-Nielsen staining and in large quantities by fluorescence and IHC studies.

CONCLUSION

There is evidence for the ability of mycobacteria to have morphological polymorphism and for the need to clarify the pathogenesis of tuberculosis.

Mixed Infection of Mycobacterium abscessus subsp. abscessus and Mycobacterium tuberculosis in the Lung

A mixed infection of Mycobacterium abscessus subsp. abscessus (Mab) and Mycobacterium tuberculosis (MTB) in the lung is an unusual clinical manifestation and has not yet been reported. A 61-year-old woman had been treated for Mab lung disease and concomitant pneumonia, and was diagnosed with pulmonary tuberculosis (PTB). Despite both anti-PTB and anti-Mab therapy, her entire left lung was destroyed and collapsed. She underwent left pneumonectomy and received medical therapy. We were able to successfully treat her mixed infection by pneumonectomy followed by inhaled amikacin therapy. To the best of our knowledge, thus far, this is the first description of a mixed Mab and MTB lung infection.

Mycobacterium Tuberculosis and Nontuberculous Mycobacteria Coinfection of the Lungs

Tuberculosis is highly prevalent in our country and nontuberculous mycobacteria (NTM) are frequently found in respiratory specimens recently. A 65-year-old woman was admitted with complaints of fever, cough, weight loss, and hemoptysis. On the patient's chest radiography an upper lobe cavity in both lungs and consolidation was detected. Acid-fast bacilli 4+ were observed in smear of sputum and culture results M. intracellulare and M. tuberculosis were observed together. The patient's treatment was arranged. Through this case, we want to emphasize that tuberculosis and nontuberculous mycobacterial disease can coexist.

The performance of interferon-gamma release assay in nontuberculous mycobacterial diseases: a retrospective study in China

Background

The interferon-gamma release assay (IGRA) is more specific than the tuberculin skin test to discriminate between tuberculosis (TB) and nontuberculous mycobacterial (NTM) diseases. Here we performed a retrospective study to evaluate the performance of the T-SPOT.TB in patients with NTM diseases.

Methods

Between March, 2013 and Nov, 2015, a total of 58 patients with NTM diseases had a T-SPOT.TB performed were enrolled, 30 patients had definite NTM diseases, 28 had probable diseases. Their clinicopathological characteristics were reviewed and analyzed. Cultures for mycobacteria were performed. The indirect proportion method with Löwenstein–Jensen (L-J) medium was used for first-line drug susceptibility test. T-SPOT.TB assay was performed according to the manufacturer’s instructions. Data were expressed as mean ± standard deviation (continuous variables) and as numbers and percentages (categorical variables). The χ² test was used for comparisons between proportions.

Results

The average age was 51.8 ± 16.1 years (range 10 to 77 years), 58.6% (34/58) were male. 16.4% (9/55) were TB-PCR positive. 34 (58.6%) isolates were Mycobacterium intracellulare, ten (17.2%) were Mycobacterium chelonae and seven (12.1%) were Mycobacterium fortuitum. Fifty-two (89.7%) patients were NTM lung disease, five (8.6%) were pleural disease, and one (1.7%) lymphadenitis. The total positivity of T-SPOT.TB was 53.4% (31/58) among the whole group (probable and definite). For probable cases, the T-SPOT.TB assay was positive in 53.5% (15/28); for definite cases, 16 (53.3%) of 30 definite cases were positive. There was no statistical difference in the positivity rate between them (P < 0.01).

Conclusions

In the study, we showed that a significant portion of NTM diseases were T-SPOT.TB positive in China. Although T-SPOT.TB is useful diagnostic method for differentiating TB from NTM diseases, in China, the IGRA assay show limited value in the discrimination. In addition, further research is needed to investigate the association between TB infection and treatment for NTM patients.

Performance of an in-house real-time polymerase chain reaction for identification of Mycobacterium tuberculosis isolates in laboratory routine diagnosis from a high burden setting

Brazil is one of the high burden countries for tuberculosis, and a rapid diagnosis is essential for effective control of the disease. In the present study, an in-house real-time polymerase chain reaction (PCR) assay targeting the mpt64 gene for identification of Mycobacterium tuberculosis complex isolates was evaluated under routine diagnosis conditions in a reference laboratory. From May 2011 to July 2012, 1,520 isolates of mycobacteria were prospectively submitted for phenotypic and/or PRA-hsp65 identification and to real-time PCR. The mpt64 real-time PCR showed 99.7% sensitivity and 96% specificity and detected 79.4% of the cases missed by phenotypic and PRA-hsp65 identification. The in-house real-time PCR assay showed high sensitivity and specificity and was successfully implemented in the routine diagnosis of tuberculosis in a reference laboratory from a high burden setting.

Update on pulmonary disease due to non-tuberculous mycobacteria

Non-tuberculous mycobacteria (NTM) are emerging worldwide as significant causes of chronic pulmonary infection, posing a number of challenges for both clinicians and researchers. While a number of studies worldwide have described an increasing prevalence of NTM pulmonary disease over time, population-based data are relatively sparse and subject to ascertainment bias. Furthermore, the disease is geographically heterogeneous. While some species are commonly implicated worldwide (Mycobacterium avium complex, Mycobacterium abscessus), others (e.g., Mycobacterium malmoense, Mycobacterium xenopi) are regionally important. Thoracic computed tomography, microbiological testing with identification to the species level, and local epidemiology must all be taken into account to accurately diagnose NTM pulmonary disease. A diagnosis of NTM pulmonary disease does not necessarily imply that treatment is required; a patient-centered approach is essential. When treatment is required, multidrug therapy based on appropriate susceptibility testing for the species in question should be used. New diagnostic and therapeutic modalities are needed to optimize the management of these complicated infections.

Non-tuberculous mycobacteria: baseline data from three sites in Papua New Guinea, 2010-2012

OBJECTIVE

To determine the proportion of non-tuberculous mycobacteria (NTM) in samples of pulmonary tuberculosis (TB) cases from Papua New Guinea who were diagnosed using acid-fast microscopy.

METHODS

As part of a case detection study for TB, conducted in three provincial hospitals in Papua New Guinea, sputum samples of suspected tuberculous cases aged 15 years or older were collected from November 2010 to July 2012. Mycobacterial species isolated from sputum and grown in culture were examined to distinguish between NTM and the Mycobacterium tuberculosis complex (MTBC).

RESULTS

NTM were detected in 4% (9/225) of sputum samples grown in culture. Five (2.2%) of them were identified as NTM only and four (1.8%) were identified as mixed cultures containing both MTBC and NTM. Four different NTM species were identified; M. fortuitum, M. intracellulare, M. terrae and M. avium.

DISCUSSION

This is the first report from Papua New Guinea identifying NTM in three different locations. As NTM cannot be distinguished from M. tuberculosis through smear microscopy, the presence of NTM can lead to a false-positive diagnosis of tuberculosis. The prevalence of NTM should be determined and a diagnostic algorithm developed to confirm acid-fast bacilli in a smear as M. tuberculosis.

The significance of Mycobacterium abscessus subspecies abscessus isolation during Mycobacterium avium complex lung disease therapy

BACKGROUND

Isolation of Mycobacterium abscessus subspecies abscessus (MAA) is common during Mycobacterium avium complex (MAC) lung disease therapy, but there is limited information about the clinical significance of the MAA isolates.

METHODS

We identified 53 of 180 patients (29%) treated for MAC lung disease who had isolation of MAA during MAC lung disease therapy. Patients were divided into those without (group 1) and those with (group 2) MAA lung disease.

RESULTS

There were no significant demographic differences between patients with and without MAA isolation or between groups 1 and 2. Group 1 and 2 patients had similar total sputum cultures obtained (P = .7; 95% CI, -13.4 to 8.6) and length of follow-up (P = .8; 95% CI, -21.5 to 16.1). Group 2 patients had significantly more total positive cultures for MAA (mean±SD, 15.0 ± 11.1 vs 1.2 ± 0.4; P < .0001; 95% CI, -17.7 to -9.9), were significantly more likely to develop new or enlarging cavitary lesions while on MAC therapy (P > .0001), and were significantly more likely to meet all three American Thoracic Society diagnostic criteria for nontuberculous mycobacterial disease (21 of 21 [100%] vs 0 of 32 [0%]; P < .0001) compared with group 1 patients. Group 1 patients were significantly more likely to have single, positive MAA cultures than group 2 patients (25 of 31 vs 0 of 21; P < .0001).

CONCLUSIONS

Microbiologic and clinical follow-up after completion of MAC lung disease therapy is required to determine the significance of MAA isolated during MAC lung disease therapy. Single MAA isolates are not likely to be clinically significant.

Nontuberculous Mycobacteria in Noncystic Fibrosis Bronchiectasis

During the past decades, a growing interest has been raised in evaluating nontuberculous mycobacteria (NTM) in patients with noncystic fibrosis bronchiectasis (NCFBE). This paper reviews several aspects of the correlations between NTM and NCFBE, including pathogenesis, radiological features, diagnosis, and management. Bronchiectasis and NTM lung disease are connected, but which one comes first is still an unresolved question. The rate of NTM lung disease in NCFBE varies through the studies, from 5% to 30%. The most frequent species isolated is MAC. NCFBE patients affected by NTM infection frequently present coinfections, including both other different NTM species and microorganisms, such as P. aeruginosa. Once a diagnosis of NTM disease has been reached, the initiation of therapy is not always mandatory. NTM species isolated, patients' conditions, and disease severity and its evolution should be considered. Risk factors for disease progression in NCFBE patients with NTM are low body mass index, cavitary disease, consolidations, and macrolide resistance at presentation.

[Identification of mycobacteria to the species level by molecular methods in the Public Health Laboratory of Bogotá, Colombia]

INTRODUCTION

Global epidemiology of non-tuberculous mycobacteria (NTM) is unknown due to the fact that notification is not required in many countries, however the number of infection reports and outbreaks caused by NTM suggest a significant increase in the last years. Traditionally, mycobacteria identification is made through biochemical profiles which allow to differentiate M. tuberculosis from NTM, and in some cases the mycobacteria species. Nevertheless, these methods are technically cumbersome and time consuming. On the other hand, the introduction of methods based on molecular biology has improved the laboratory diagnosis of NTM.

OBJECTIVE

To establish the NTM frequency in positive cultures for acid-fast bacilli (AAFB) which were sent to Laboratorio de Salud Pública de Bogotá over a 12 month period.

MATERIALS AND METHODS

A total of 100 positive cultures for acid-fast bacilli from public and private hospitals from Bogotá were identified by both biochemical methods and the molecular methods PRA (PCR-restriction enzyme analysis) and multiplex-PCR. Furthermore, low prevalence mycobacteria species and non-interpretable results were confirmed by 16SrDNA sequentiation analysis.

RESULTS

Identification using the PRA method showed NMT occurrence in 11% of cultures. In addition, this molecular methodology allowed to detect the occurrence of more than one mycobacteria in 4% of the cultures. Interestingly, a new M. kubicae pattern of PCR-restriction analysis is reported in our study.

CONCLUSION

Using a mycobacteria identification algorithm, which includes the molecular method PRA, improves the diagnostic power of conventional methods and could help to advance both NTM epidemiology knowledge and mycobacteriosis control.

Direct identification of mycobacteria from clinical specimens by multiplex real-time PCR

AIMS

To directly identify clinically relevant mycobacteria from clinical specimens, we have developed a multiplex real-time PCR assay with hydrolysis probes that can identify 20 mycobacterial species.

METHODS AND RESULTS

The assay was initially evaluated using 248 strains, including both reference strains and clinical isolates. Then, the assay was implemented according to a scheme in our laboratory. The scheme based on the clinical differences between the Mycobacterium tuberculosis complex (MTC) and nontuberculous mycobacteria (NTM) consisted of three stepwise PCRs. MTC and NTM were differentially detected in the step 1 PCR, and the NTM species were identified in the step 2 and step 3 PCRs. During a 2·5-year period, 1877 isolates of MTC (1142 directly recovered from clinical specimens) and 596 isolates of NTM (143 directly recovered from clinical specimens) were detected, and the species of 590 (99·0%) of the 596 NTM isolates were identified.

CONCLUSIONS

Our experience shows that this is a new paradigm for rapidly and accurately identifying clinically relevant mycobacteria, in which a multiplex real-time PCR assay is directly applied to clinical specimens in a stepwise fashion.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first report of a multiplex real-time PCR assay for identifying clinically important mycobacterial species directly from clinical specimens and its application in a clinical microbiology laboratory.

The effectiveness of real-time PCR assay, compared with microbiologic results for the diagnosis of pulmonary tuberculosis

Background

The incidence of tuberculosis (TB) in Korea is relatively high compared to the other Organisation for Economic Co-operation and Development (OECD) countries, with a prevalence of 71 per 100,000 in 2012, although the incidence is declining. Real-time polymerase chain reaction (PCR) has been introduced for the rapid diagnosis of TB. Recently, its advantage lies in higher sensitivity and specificity for the diagnosis of TB. This study evaluated the clinical accuracy of real-time PCR using respiratory specimens in a clinical setting.

Methods

Real-time PCR assays using sputum specimens and/or bronchoscopic aspirates from 2,877 subjects were reviewed retrospectively; 2,859 subjects were enrolled. The diagnosis of TB was determined by positive microbiology, pathological findings of TB in the lung and pleura, or clinical suspicion of active TB following anti-TB medication for more than 6 months with a favorable response.

Results

Sensitivity, specificity, and accuracy were 44%, 99%, and 86% from sputum, and 65%, 97%, and 87% from bronchoscopic aspirates, respectively. For overall respiratory specimens, sensitivity was 59%, specificity was 98%, and accuracy increased to 89%.

Conclusion

Positivity in real-time PCR using any respiratory specimens suggests the possibility of active TB in clinically suspected cases, guiding to start anti-TB medication. Real-time PCR from selective bronchoscopic aspirates enhances the diagnostic yield much more when added to sputum examination.