Biosensors for the detection of Mycobacterium tuberculosis: a comprehensive overview

Advances in the detection and diagnosis of tuberculosis using optical-based devices

Tuberculosis (TB), a bacterial infection caused by Mycobacterium tuberculosis, is highly contagious and can lead to severe health complications if left untreated. This review article discusses the importance of early detection and treatment and its global incidence and epidemiology, emphasizing its impact on vulnerable populations and its role as a major cause of death worldwide. Furthermore, it highlights the challenges faced with diagnosing TB. To overcome these challenges, point-of-care devices have emerged as promising tools for rapid and accurate TB detection. These include devices such as nucleic acid amplification tests (NAATs), lateral flow assays (LFAs), and microfluidic-based assays, which offer advantages such as rapid results, portability, and the ability to detect drug-resistant strains. Optical-based devices, such as photonic micro-ring sensors, silicon platform-based sensors, plasmonic-based platforms, microfluidics, and smartphone imaging, are some of the highlighted optical-based devices with the potential to detect TB. These devices can detect TB in sputum samples with high sensitivity and specificity. Optical-based diagnostic devices have the potential to offer the advantages of detecting low concentrations of target molecules and being adaptable to detect multiple targets simultaneously. Using these devices in a clinical setting makes them suitable for their application in improving access to diagnostic testing that enables earlier detection and treatment of TB. Furthermore, these devices would improve TB's global health issue, which requires comprehensive research, prevention, and treatment efforts.

Evolution of tuberculosis diagnostics: From molecular strategies to nanodiagnostics

Tuberculosis has remained a global concern for public health affecting the lives of people for ages. Approximately 10 million people are affected by the disease and 1.5 million succumb to the disease worldwide annually. The COVID-19 pandemic has highlighted the role of early diagnosis to win the battle against such infectious diseases. Thus, advancement in the diagnostic approaches to provide early detection forms the foundation to eradicate and manage contagious diseases like tuberculosis. The conventional diagnostic strategies include microscopic examination, chest X-ray and tuberculin skin test. The limitations associated with sensitivity and specificity of these tests demands for exploring new techniques like probe-based assays, CRISPR-Cas and microRNA detection. The aim of the current review is to envisage the correlation between both the conventional and the newer approaches to enhance the specificity and sensitivity. A significant emphasis has been placed upon nanodiagnostic approaches manipulating quantum dots, magnetic nanoparticles, and biosensors for accurate diagnosis of latent, active and drug-resistant TB. Additionally, we would like to ponder upon a reliable method that is cost-effective, reproducible, require minimal infrastructure and provide point-of-care to the patients.

Point-of-care test for tuberculosis: a boon in diagnosis

Rapid diagnosis of tuberculosis (TB) is an effective measure to eradicate this infectious disease worldwide. Traditional methods for screening TB patients do not provide an immediate diagnosis and thus delay treatment. There is an urgent need for the early detection of TB through point-of-care tests (POCTs). Several POCTs are widely available at primary healthcare facilities that assist in TB screening. In addition to the currently used POCTs, advancements in technology have led to the discovery of newer methods that provide accurate and fast information independent of access to laboratory facilities. In the present article, the authors tried to include and describe the potential POCTs for screening TB in patients. Several molecular diagnostic tests, such as nucleic acid amplification tests, including GeneXpert and TB-loop-mediated isothermal amplification, are currently being used as POCTs. Besides these methods, the pathogenic component of Mycobacterium tuberculosis can also be utilized as a biomarker for screening purposes through immunological assays. Similarly, the host immune response to infection has also been utilized as a marker for the diagnosis of TB. These novel biomarkers might include Mtb85, interferon-γ inducible protein-10, volatile organic compounds, acute-phase proteins, etc. Radiological tests have also been observed as POCTs in the TB screening POCT panel. Various POCTs are performed on samples other than sputum, which further eases the screening process. These POCTs should not require large-scale manpower and infrastructure. Hence, POCT should be able to identify patients with M. tuberculosis infection at the primary healthcare level only. There are several other advanced techniques that have been proposed as future POCTs and have been discussed in the present article.

Undiagnosed and missed active pulmonary tuberculosis during mass gatherings: a prospective cross-sectional study from the Hajj pilgrimage

Mass gatherings increase the risk of infectious diseases transmission including tuberculosis (TB). The Hajj pilgrimage to Mecca, Saudi Arabia, is attended by over 2 million pilgrims many of whom are from high TB-burden countries, and has been linked to increased risk of TB acquisition among travellers. We investigated the burden of undiagnosed and missed active pulmonary TB (PTB) among Hajj pilgrims symptomatic for cough. The study was conducted among hospitalised and non-hospitalised travellers attending the Hajj pilgrimage in 2016 and 2017. Questionnaires were used to collect relevant data and sputum samples were collected from participants and processed using the Xpert MTB-RIF assay. Non-hospitalised pilgrims (n = 1510) originating from 16 high and medium TB-burden countries were enrolled. Undiagnosed, rifampicin-sensitive, active PTB was identified in 0.7%. Comorbidities (adjOR = 5.9 [95% CI = 1.2-27.8]), close contact with a TB case (adjOR = 5.9 [95% CI = 1.2-27.8]), cough in household (adjOR = 4.46 [95% CI = 1.1-19.5]), and previous TB treatment (adjOR = 10.1 [95% CI = 4.1-98.1]) were independent risk factors for TB. Of the hospitalised pilgrims (n = 304), 2.9% were positive for PTB, and 2.3% were missed, including a rifampicin-resistant case. History of TB treatment was associated with increased risk of TB (adjOR = 8.1 [95% CI = 1.3-48.7]). International mass gatherings may play an important role in the global epidemiology of TB. Preventive measures should be directed to reducing the risk of TB importation and transmission during Hajj and other similar events.

Multicenter Testing of a Simple Molecular Diagnostic System for the Diagnosis of Mycobacterium Tuberculosis

Mycobacterium tuberculosis (MTB) is a communicable disease and still remains a threat to common health. Thus, early diagnosis and treatment are required to prevent the spread of infection. Despite the recent advances in molecular diagnostic systems, the commonly used MTB diagnostic tools are laboratory-based assays, such as mycobacterial culture, MTB PCR, and Xpert MTB/RIF. To address this limitation, point-of-care testing (POCT)-based molecular diagnostic technologies capable of sensitive and accurate detection even in environments with limited sources are needed. In this study, we propose simple tuberculosis (TB) molecular diagnostic assay by combining sample preparation and DNA-detection steps. The sample preparation is performed using a syringe filter with amine-functionalized diatomaceous earth and homobifunctional imidoester. Subsequently, the target DNA is detected by quantitative PCR (polymerase chain reaction). The results can be obtained within 2 h from samples with large volumes, without any additional instruments. The limit of detection of this system is 10 times higher than those of conventional PCR assays. We validated the clinical utility of the proposed method in 88 sputum samples obtained from four hospitals in the Republic of Korea. Overall, the sensitivity of this system was superior to those of other assays. Therefore, the proposed system can be useful for MTB diagnosis in limited-resource settings.

Role of Interferons in Mycobacterium tuberculosis Infection

Considerable measures have been implemented in healthcare institutions to screen for and treat tuberculosis (TB) in developed countries; however, in low- and middle-income countries, many individuals still suffer from TB’s deleterious effects. TB is caused by an infection from the Mycobacterium tuberculosis (M. tb) bacteria. Symptoms of TB may range from an asymptomatic latent-phase affecting the pulmonary tract to a devastating active and disseminated stage that can cause central nervous system demise, musculoskeletal impairments, and genitourinary compromise. Following M. tb infection, cytokines such as interferons (IFNs) are released as part of the host immune response. Three main classes of IFNs prevalent during the immune defense include: type I IFN (α and β), type II IFN (IFN-γ), and type III IFN (IFN-λ). The current literature reports that type I IFN plays a role in diminishing the host defense against M. tb by attenuating T-cell activation. In opposition, T-cell activation drives type II IFN release, which is the primary cytokine mediating protection from M. tb by stimulating macrophages and their oxidative defense mechanisms. Type III IFN has a subsidiary part in improving the Th1 response for host cell protection against M. tb. Based on the current evidence available, our group aims to summarize the role that each IFN serves in TB within this literature review.

Evaluation of modified bleach technique for the detection of acid fast bacilli in lymph node aspirate at the University of Gondar Comprehensive Specialized Hospital, Northwest Ethiopia

Background

Tuberculous Lymphadenitis (TBLN) is the commonest form of extrapulmonary tuberculosis. Definitive diagnosis of TBLN is difficult due to the low efficacy of the routine diagnostic techniques as compared to culture.

Objective

To determine whether prior bleach concentration can improve the detection of acid-fast bacilli when compared with conventional Ziehl-Neelsen (ZN) staining by using culture as the gold standard.

Methods

Cross-sectional study was conducted from March 01, 2015 to May 30, 2015. The study subjects were clinically suspected TBLN patients. Fine needle aspiration (FNA) was performed. Two different smears were prepared directly from the first needle pass for cytology and ZN staining. The remaining aspirate was used for the modified bleach concentration. The second needle pass aspirate was transferred into a sterile container containing sterile normal saline. The sediment was inoculated on the Lowenstein Jensen (LJ) medium. Measurement parameters for reliability and validity were used to analyze the results.

Result

A total of 93 participants were included in the study. Fifty-six out of the 93 (60.2 %) cases were positive for mycobacterium tuberculosis complex on LJ culture. The detection rates of direct ZN staining and modified bleach method were 20.4 % and 44.1 %, respectively. 73.1 % of the cases showed cytomorphological features consistent with TBLN by cytologic examination. The sensitivities of direct ZN staining and modified bleach method and cytomorphology were 32.0 %, 67.8 %, and 92.8 %, respectively.

Conclusion

Implementation of bleach concentration increases the detection rate of AFB over the direct ZN method. The bleach method can also be easily performed and provide a safe working environment by reducing infections.