Evaluation of the Speed-Oligo Mycobacteria assay for the identification of nontuberculous mycobacteria

Epidemiology and laboratory detection of non-tuberculous mycobacteria

The global incidence of non-tuberculous mycobacteria (NTM) infections is on the rise. This study systematically searched several databases, including PubMed, Web of Science, Google Scholar, and two Chinese libraries (Chinese National Knowledge Infrastructure and Wanfang) to identify relevant published between 2013 and 2023 related to the isolation of NTM in clinical specimens from various countries and provinces of China. Furthermore, a comprehensive literature review was conducted in PubMed and Google Scholar to identify randomized clinical trials, meta-analyses, systematic reviews, and observational studies that evaluated the diagnostic accuracy and impact of laboratory detection methods on clinical outcomes. This review presented the most recent epidemiological data and species distributions of NTM isolates in several countries and provinces of China. Moreover, it provided insights into laboratory bacteriological detection, including the identified strains, advantages and disadvantages, recent advancements, and the commercial Mycobacterium identification kits available for clinical use. This review aimed to aid healthcare workers in understanding this aspect, enhance the standards of clinical diagnosis and treatment, and enlighten them on the existing gaps and future research priorities.

Culture, Identification, and Antimicrobial Susceptibility Testing of Pulmonary Nontuberculous Mycobacteria

Nontuberculous mycobacteria (NTM) typically cause opportunistic pulmonary infections and reliable laboratory results can assist with diagnosis of disease. Microscopy can detect acid-fast bacilli from specimens though it has poor sensitivity. Solid and liquid culture are used to grow NTM, which are identified by molecular or protein-based assays. Because culture has a long turnaround time, some assays are designed to identify NTM directly from sputum specimens. When indicated, phenotypic susceptibility testing should be performed by broth microdilution as per the guidelines from the Clinical Laboratory Standards Institute. Genotypic susceptibility methods may be used to decrease the turnaround time for some antimicrobials.

A cold-blooded tiptoer: non-resolving cellulitis in an immunocompromised patient

Mycobacterium haemophilum is a nontuberculous mycobacteria (NTM) with a predilection for skin and soft tissue infection (SSTI) in the immunocompromised host. We report a case of disseminated M haemophilum infection initially presenting as a nonresolving subacute cellulitis of bilateral lower extremities. Genetic sequencing was used for final identification, while a commercially available polymerase chain reaction test returned a false-positive result for Mycobacterium intracellulare. Consequently, we highlight the importance of M haemophilum as a major differential diagnosis of SSTI in the immunocompromised host and the need for careful interpretation of rapid diagnostic tests.

Profile of Nontuberculous Mycobacteria in Patients Suspected of Tuberculosis and Drug-Resistant Tuberculosis

Objective  Infections due to nontuberculous mycobacteria (NTM) is increasing globally and may present as drug-resistant tuberculosis (DRTB). In India, data on NTM prevalence and species diversity is limited. Present study was conducted to detect the prevalence and profile of NTM among patients suspected of DRTB using paraffin slide culture (PSC)and mycobacteria growth indicator tube (MGIT) culture methods for isolation of NTM. Material and Method  A total of 2,938 samples suspected of TB/DRTB were cultured on PSC and MGIT960. Species identification of mycobacterial isolate was done by sequencing of 16s ribosomal RNA gene. Result  Among 2938 samples, 35 (1.19%) were found positive for NTM by PSC and 9 (0.30%) were found positive by MGIT. The diversity of NTM species was high (13 species). Out of 35 NTM isolates by PSC, maximum 34.29% (12) isolates were found to be Mycobacterium fortuitum , followed by 11.43% (4) Mycobacterium abscessus and Mycobacterium chelonae , and 42.85% (15) were other species viz. 8.57% (3) were Mycobacterium intracellulare and Mycobacterium kansasii , 5.71% (2) were Mycobacterium peregrinum , and 2.85% (1) were Mycobacterium flavescens, Mycobacterium farcinogenes, Mycobacterium moriokanese, Mycobacterium wolinskyi, Mycobacterium simiae, Mycobacterium goodii , and Mycobacterium terrae each. Coinfection of Mycobacterium tuberculosis (MTB) and NTM was found in 60% (21) samples. Conclusion  Prevalence of NTM was low among multidrug resistant tuberculosis/TB suspected patients, similar to other studies done in India. PSC was found better than MGIT for the isolation of NTM, though poor separation of NTM and MTB on subculture may have led to false negativity in cases of coinfection. About 13 species were isolated; M. fortuitum was the most common of all. Since coinfection of NTM and TB can also occur, samples of patients suspected of NTM should be cultured on PSC even if positive for MTB.

Evaluation of Q Gene Mycobacteria: A novel and easy nucleic acid chromatography method for mycobacterial species identification

OBJECTIVES

A simple, rapid, and new diagnostic test for mycobacteria, named Q Gene Mycobacteria, has been developed. It is based on multiplex PCR using primers harbouring DNA tags combined with a dipstick nucleic acid chromatography method, which does not require the denaturation of PCR products for hybridization and can identify five species of mycobacteria including Mycobacterium tuberculosis complex (MTC), Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium kansasii, and Mycobacterium gordonae. This study aimed to evaluate Q Gene Mycobacteria for the accurate identification of these five species.

METHODS

A total of 340 mycobacterial strains/isolates were tested, of which 159 were type strains (four MTC and 155 non-tuberculosis mycobacteria (NTM) including four subspecies) and 181 were clinical isolates (18 M. tuberculosis, two Mycobacterium bovis Bacillus Calmette et Guérin (BCG), and 161 NTM comprising 16 species) collected from eight laboratories and hospitals in Japan. Species identification of NTM isolates was performed using the DNA-DNA hybridization method and/or direct sequencing of 16S rRNA, hsp65, and rpoB genes. Q Gene Mycobacteria was compared with above conventional methods for identifying the five species.

RESULTS

Q Gene Mycobacteria showed excellent concordance for species identification, specifically 99.4% (158/159) for type strains and 99.4% (180/181) for clinical isolates. The two strains that were misidentified as M. gordonae were Mycobacterium paragordonae. As they are genetically close and there is few case reports of M. paragordonae, it might not be a serious critical issue to distinguish M. paragordonae from M. gordonae.

CONCLUSIONS

Q Gene Mycobacteria was able to identify frequently isolated mycobacterial species accurately and easily. Therefore, Q Gene Mycobacteria could be a useful tool for the identification of specific mycobacteria in clinical laboratories.

Mycobacterium avium: an overview

Mycobacterium avium is an environmental microorganism found in soil and water sources worldwide. It is the most prevalent species of nontuberculous mycobacteria that causes infectious diseases, especially in immunocompromised individuals. This review discusses and highlights key topics about M. avium, such as epidemiology, pathogenicity, glycopeptidolipids, laboratory identification, genotyping, antimicrobial therapy and antimicrobial resistance. Additionally, the main comorbidities associated with M. avium infection are discussed.

Recent advances in molecular diagnostics and understanding mechanisms of drug resistance in nontuberculous mycobacterial diseases

Accumulating evidence suggests that human infections caused by nontuberculous mycobacteria (NTM) are increasing worldwide, indicating that NTM disease is no longer uncommon in many countries. As a result of an increasing emphasis on the importance of differential identification of NTM species, several molecular tools have recently been introduced in clinical and experimental settings. These advances have led to a much better understanding of the diversity of NTM species with regard to clinical aspects and the potential factors responsible for drug resistance that influence the different outcomes of NTM disease. In this paper, we review currently available molecular diagnostics for identification and differentiation of NTM species by summarizing data from recently applied methods, including commercially available assays, and their relevant strengths and weaknesses. We also highlight drug resistance-associated genes in clinically important NTM species. Understanding the basis for different treatment outcomes with different causative species and drug-resistance mechanisms will eventually improve current treatment regimens and facilitate the development of better control measures for NTM diseases.

Comparative evaluation of the AdvanSure Mycobacteria GenoBlot assay and the GenoType Mycobacterium CM/AS assay for the identification of non-tuberculous mycobacteria

In this study, to assess the performance of the AdvanSure Mycobacteria GenoBlot assay (AdvanSure assay), we compared its performance with that of the GenoType Mycobacterium CM/AS assay (GenoType assay) for the identification of non-tuberculous mycobacteria (NTM). Twenty-four reference strains and 103 consecutive clinical NTM isolates were analysed. The accuracy rates for the 24 reference strains were 87.5 and 95.8 % for the AdvanSure and GenoType assays, respectively. For the 103 clinical isolates, a 91.3 % (94/103) concordance rate was observed between the two assays. The majority (7/9) of discrepancies were isolates identified as Mycobacterium avium complex (MAC) by only the AdvanSure assay. All of these isolates except one were confirmed as MAC by sequence-based typing. The AdvanSure assay showed comparable performance to the GenoType assay and can be useful as a routine method for NTM identification in the clinical setting, especially where MAC is the main cause of NTM infection.