Application of metagenomic next-generation sequencing for bronchoalveolar lavage diagnostics in patients with lower respiratory tract infections

Metagenomic next-generation sequencing targeted and metagenomic next-generation sequencing for pulmonary infection in HIV-infected and non-HIV-infected individuals

Background

When individuals infected with human immunodeficiency virus (HIV) experience pulmonary infections, they often exhibit severe symptoms and face a grim prognosis. Consequently, early, rapid, and accurate pathogen diagnosis is vital for informing effective treatment strategies. This study aimed to use metagenomic next-generation sequencing (mNGS) and targeted mNGS (tNGS) to elucidate the characteristics of pulmonary infections in HIV and non-HIV individuals.

Methods

This study enrolled 90 patients with pulmonary infection at the Department of Infectious Diseases of The First Hospital of Jilin University from June 2022 to May 2023, and they were divided into HIV (n=46) and non-HIV (n=44) infection groups. Their bronchoalveolar lavage fluid (BALF) was collected for mNGS analysis to evaluate the differences in pulmonary infection pathogens, and tNGS detection was performed on BALF samples from 15 HIV-infected patients.

Results

A total of 37 pathogens were identified in this study, including 21 bacteria, 5 fungi, 5 viruses, 5 mycobacteria, and 1 mycoplasma. The sensitivity of mNGS was 78.9% (71/90), which is significantly higher than that of conventional methods (CTM) (39/90, P=1.5E-8). The combination of mNGS with CTM can greatly enhance the sensitivity of pathogen detection. The prevalence of Pneumocystis jirovecii (82.6% vs. 9.1%), cytomegalovirus (CMV) (58.7% vs. 0%), and Epstein-Barr virus (EBV) (17.4% vs. 2.3%) was significantly higher in the HIV infection group than in the non-HIV infection group (P<0.05). Although no statistically significant difference was observed, the detection rate of Mycobacteria was higher in HIV-infected patients (17.4%) than in the non-HIV group (6.8%). Furthermore, the tNGS results of BALF from 15 HIV-infected patients were not entirely consistent with the mNGS results., and the concordance rate of tNGS for the detection of main pathogens reached 86.7% (13/15).

Conclusion

Next-generation sequencing (NGS) can accurately detect pathogens in the BALF of patients with pulmonary infection. The sensitivity of tNGS is comparable to that of mNGS. Therefore, this technique should be promoted in the clinic for better patient outcomes.

Application of Second-Generation Sequencing Technology in Lower Respiratory Tract Infection

BACKGROUND

Lower respiratory tract infection (LRTI) has long been an important threat to people's life and health, so the rapid diagnosis of LRTI is of great significance in clinical treatment. In recent years, the development of the sequencing technology provides a new direction for the rapid diagnosis of LRTI. In this review, the advantages and disadvantages of second-generation sequencing techniques represented by metagenomics next-generation sequencing (mNGS) and droplet digital polymerase chain reaction (ddPCR) in LRTI were reviewed. Furthermore, it offers insights into the future trajectory of this technology, highlighting its potential to revolutionise the field of respiratory infection diagnostics.

OBJECTIVE

This review summarises developments in mechanistic research of second-generation sequencing technology their relationship with clinical practice, providing insights for future research.

METHODS

Authors conducted a search on PubMed and Web of Science using the professional terms 'Lower respiratory tract infection' and 'droplet digital polymerase chain reaction' and 'metagenomics next generation sequencing'. The obtained literature was then roughly categorised based on their research content. Similar studies were grouped into the same sections, and further searches were conducted based on the keywords of each section.

RESULTS

Different studies discussed the application of second-generation sequencing technology in LRTI from different angles, including the detection of pathogens of LRTI by mNGS and ddPCR, the prediction ability of drug-resistant bacteria, and comparison with traditional methods. We try to analyse the advantages and disadvantages of the second-generation sequencing technology by combing the research results of mNGS and ddPCR. In addition, the development direction of the second-generation sequencing technology is prospected.

Metatranscriptomics: A Tool for Clinical Metagenomics

In the field of bioinformatics, amplicon sequencing of 16S rRNA genes has long been used to investigate community membership and taxonomic abundance in microbiome studies. As we can observe, shotgun metagenomics has become the dominant method in this field. This is largely owing to advancements in sequencing technology, which now allow for random sequencing of the entire genetic content of a microbiome. Furthermore, this method allows profiling both genes and the microbiome's membership. Although these methods have provided extensive insights into various microbiomes, they solely assess the existence of organisms or genes, without determining their active role within the microbiome. Microbiome scholarship now includes metatranscriptomics to decipher how a community of microorganisms responds to changing environmental conditions over a period of time. Metagenomic studies identify the microbes that make up a community but metatranscriptomics explores the diversity of active genes within that community, understanding their expression profile and observing how these genes respond to changes in environmental conditions. This expert review article offers a critical examination of the computational metatranscriptomics tools for studying the transcriptomes of microbial communities. First, we unpack the reasons behind the need for community transcriptomics. Second, we explore the prospects and challenges of metatranscriptomic workflows, starting with isolation and sequencing of the RNA community, then moving on to bioinformatics approaches for quantifying RNA features, and statistical techniques for detecting differential expression in a community. Finally, we discuss strengths and shortcomings in relation to other microbiome analysis approaches, pipelines, use cases and limitations, and contextualize metatranscriptomics as a tool for clinical metagenomics.

Clinical metagenomics-challenges and future prospects

Infections lacking precise diagnosis are often caused by a rare or uncharacterized pathogen, a combination of pathogens, or a known pathogen carrying undocumented or newly acquired genes. Despite medical advances in infectious disease diagnostics, many patients still experience mortality or long-term consequences due to undiagnosed or misdiagnosed infections. Thus, there is a need for an exhaustive and universal diagnostic strategy to reduce the fraction of undocumented infections. Compared to conventional diagnostics, metagenomic next-generation sequencing (mNGS) is a promising, culture-independent sequencing technology that is sensitive to detecting rare, novel, and unexpected pathogens with no preconception. Despite the fact that several studies and case reports have identified the effectiveness of mNGS in improving clinical diagnosis, there are obvious shortcomings in terms of sensitivity, specificity, costs, standardization of bioinformatic pipelines, and interpretation of findings that limit the integration of mNGS into clinical practice. Therefore, physicians must understand the potential benefits and drawbacks of mNGS when applying it to clinical practice. In this review, we will examine the current accomplishments, efficacy, and restrictions of mNGS in relation to conventional diagnostic methods. Furthermore, we will suggest potential approaches to enhance mNGS to its maximum capacity as a clinical diagnostic tool for identifying severe infections.

Case report: Acute Talaromyces marneffei mediastinitis in an HIV-negative patient

Talaromyces marneffei (T. marneffei) is one of the most important opportunistic human pathogens endemic in Southeast Asia. Talaromycosis, which was once regarded as an opportunistic infectious disease in patients with acquired immunodeficiency syndrome, is being increasingly reported in HIV-negative populations. Since T. marneffei infection can be localized or disseminated, patients may present with a variety of symptoms. However, mediastinal infection attributed to T. marneffei is extremely rare. We report the case of a 32-year-old female who manifested a large mediastinal mass and was eventually diagnosed as acute T. marneffei mediastinitis. The patient was HIV-negative and had no direct contact with intermediate hosts. We successfully managed to treat the patient with inhaled amphotericin B deoxycholate and observed lesion absorption in subsequent CT examinations. To our knowledge, this is the first published case of T. marneffei mediastinitis and first use of inhaled antifungal monotherapy on patients with T. marneffei infection.