Interferon Gamma Release Assays in Patients with Respiratory Isolates of Non-Tuberculous Mycobacteria - a Preliminary Study

Nontuberculous mycobacteriosis oligoarthritis of the right hand misdiagnosed as rheumatoid arthritis: A case report

Infection with Mycobacterium marinum has several different clinical presentations. Most commonly, it appears as a solitary papulonodular lesion on an extremity. A rare presentation of osteoarticular M. marinum involving multiple small joints and tenosynovitis of the hand, which was misdiagnosed as rheumatoid arthritis, is reported. The patient was initially treated for seronegative rheumatoid arthritis but failed to respond to methotrexate. Magnetic resonance imaging showed arthritis and tenosynovitis. Subsequently, synovial biopsy led to histological and microbiological diagnosis. Antimycobacterial treatment should be started promptly in such cases. The combined use of rifampicin, ethambutol, and clarithromycin appears to be effective, and debridement is indicated in patients with deep-seated infections.

Current status and future landscape of diagnosing tuberculosis infection

Interferon-γ release assays (IGRAs), such as QuantiFERON-TB Gold (QFT) or T-SPOT.TB, are frequently used as tools for the diagnosis of tuberculosis (TB) infection in the 21st century. QFT-Plus recently emerged as the fourth generation of QFT assays and has replaced QFT In-Tube. However, IGRAs have several problems regarding the identification of active, latent, and cured TB infection, and the time-consuming diagnosis of TB infection because of the overnight incubation of clinical specimens or complexity of measuring the level of interferon (IFN)-γ. To easily diagnose TB infection and quickly compare it with conventional IGRAs, many in vitro tests are developed based on assays other than enzyme-linked immunosorbent assay or enzyme-linked immunospot, such as the fluorescent lateral flow assay that requires less manual operation and a shorter time. Simplified versions of IGRAs are emerging, including QIAreach QuantiFERON-TB. On the other hand, to distinguish active TB from latent or cured TB infection, new immunodiagnostic biomarkers beyond IFN-γ are evaluated using QFT supernatants. While IFN-γ or IFN-γ-related chemokine such as IFN-γ induced protein 10 is a potential biomarker in patients with active TB, interleukin-2 or latency-associated antigen such as heparin-binding hemagglutinin may be useful to distinguish active TB from latent or cured TB infection. There are no potential biomarkers to fully distinguish the time-phase of TB infection at present. It is necessary to discover new immunodiagnostic biomarkers to facilitate decisions on treatment selection for active or latent TB infection.

Performance of Interferon-γ Release Assays in Patients with Mycobacterium kansasii Infection

Objective

To evaluate the performance of interferon-γ release assays (IGRAs) in patients with Mycobacterium kansasii infection.

Methods

Consecutive patients between May 2012 and June 2021 who had positive for mycobacterial cultures and who underwent IGRAs (T-SPOT.TB or QuantiFERON-TB Gold [QFT-G]) were included in the analysis. The IGRA positivity rates among patients with M. kansasii isolates were then calculated. If M. kansasii was identified in at least two sputum samples or in sterile samples, M. kansasii disease was then diagnosed. Otherwise, colonisation was considered.

Results

During the study period, 54 patients with M. kansasii infection underwent T-SPOT.TB (n=48) or QFT-G (n=6) assays. The mean age was 44.1±13.4 years, 85.2% (46/54) were male. Eight patients were diagnosed with M. kansasii disease and another 46 patients were considered to have colonisation. Twenty-four patients (T-SPOT.TB, n=23; QFT-G, n=1) were positive for IGRAs, for an overall rate of 44.4% (24/54; T-SPOT.TB, 47.9% [23/48]; QFT-G, 16.7% [1/6]) for IGRAs, 25.0% (2/8) for M. kansasii disease, and 47.8% (22/46) for colonisation.

Conclusion

Positive IGRA rates were relatively low in patients with M. kansasii infection. More efforts are required to improve the performance of IGRAs in diagnosing M. kansasii infection.

Mandibular Nodule Caused by Mycobacterium marinum with False Positive Interferon-γ Release Assay. A Case Report

Mycobacterium marinum is a ubiquitous organism inhabiting both fresh and salt water. It can cause human diseases such as skin and soft tissue infection. The organism is also known to cause a false positive reaction to interferon-γ release assay, the test to diagnose latent tuberculosis infection. Here, we present a case of submandibular nodule caused by M. marinum with positive T-SPOT.TB test, which was likely to be false positive.

Mycobacterium chimaera as an Underestimated Cause of NTM Lung Diseases in Patients Hospitalized in Pulmonary Wards

Mycobacterium chimaera is the newly described species belonging to Mycobacterium avium complex (MAC), with morphology and growth characteristics closely related to Mycobacterium intracellulare. The aim of this retrospective study was to analyze the frequency and clinical significance of M. chimaera identification in the population of patients with previous positive respiratory cultures for M. intracellulare or MAC. 200 strains of M. intracellulare or MAC, isolated from respiratory specimens of patients hospitalized in pulmonary wards, between 2011 and 2020, were retrospectively analyzed with GenoType NTM-DR test. 88 (44%) of strains were re-classified to M. chimaera species. Analysis of clinical data in 30 patients with positive M. chimaera isolates revealed that they were diagnosed with chronic obstructive pulmonary disease (COPD) – 27%, past tuberculosis – 20%, or interstitial lung diseases – 17%, respectively. Non-tuberculous mycobacterial lung disease (NTMLD) caused by M. chimaera has been recognized in 53% of patients, most often in those presenting with post-tuberculous lung lesions. M. chimaera was almost exclusively isolated from respiratory specimens of patients with underlying lung diseases, especially those with COPD and/or past tuberculosis. NTMLD due to M. chimaera was diagnosed predominantly in patients with past tuberculosis.

Management of Infectious Lymphadenitis in Children

Lymphadenopathy is an irregularity in the size and texture of the lymph nodes, which is quite common in childhood. When the enlargement of lymph nodes is caused by inflammatory and infectious processes, it is called lymphadenitis. The main objective of this manuscript is to summarize the common infectious etiologies and presentations of lymphadenitis in children providing a management guide for clinical practice. PubMed was used to search for all of the studies published up to April 2021 using keywords such as "lymphadenitis" and "children". Literature analysis showed that the differential diagnosis for lymphadenitis in pediatrics is broad. Although lymph node enlargement in children is usually benign and self-limited, it is important to exclude malignant etiology. In most cases, history and physical examination allow to identify the correct diagnosis and start a proper treatment with a prompt resolution of the lymphadenopathy. However, particularly in the case of persistent lymphadenitis, determining the cause of lymph node enlargement may be difficult, and the exact etiology may not be identified despite extensive investigations. Further studies should develop and validate an algorithm to assist pediatricians in the diagnosis and timely treatment of lymphadenitis, suggesting situations in which a watchful waiting may be considered a safe approach, those in which empiric antibiotic therapy should be administered, and those requiring a timely diagnostic work-up.

Performance of Interferon-Gamma Release Assays in the Diagnosis of Nontuberculous Mycobacterial Diseases-A Retrospective Survey From 2011 to 2019

There is an urgent need for precise diagnosis to distinguish nontuberculous mycobacterial (NTM) diseases from pulmonary tuberculosis (PTB) and other respiratory diseases. The aim of this study is to evaluate the diagnostic performance of Interferon-gamma (IFN-γ) release assays (IGRAs), including antigen-specific peripheral blood-based quantitative T cell assay (T-SPOT.TB) and QuantiFERON-TB-Gold-Test (QFT-G), in differentiating NTM infections (N = 1,407) from culture-confirmed PTB (N = 1,828) and other respiratory diseases (N = 2,652). At specie level, 2.56%, 10.73%, and 16.49% of NTM-infected patients were infected by Mycobacterium kansasii, M. abscessus, and with M. avmm-intracellulare complex (MAC), respectively. Valid analyses of T-SPOT.TB (ESAT-6, CFP-10) and QFT-G were available for 37.03% and 85.79% in NTM-infected patients, including zero and 100% (36/36) of M. kansasii infection, 21.85% (33/151) and 92.05% (139/151) of M. abscessus infection, and 17.67% (41/232) and 91.24% (211/232) of MAC infection. Based on means comparisons and further ROC analysis, T-SPOT.TB and QFT-G performed moderate accuracy when discriminating NTM from PTB at modified cut-off values (ESAT-6 < 4 SFCs, CFP-10 < 3 SFCs, and QFT-G < 0.667 IU/ml), with corresponding AUC values of 0.7560, 0.7699, and 0.856. At species level of NTM, QFT-G effectively distinguished between MAC (AUC=0.8778), M. kansasii (AUC=0.8834) or M. abscessus (AUC=0.8783) than T-SPOT.TB. No significant differences in discriminatory power of these three IGRA tools were observed when differentiating NTM and Controls. Our results demonstrated that T-SPOT.TB and QFT-G were both efficient methods for differentiating NTM disease from PTB, and QFT-G possessed sufficient discriminatory power to distinguish infections by different NTM species.