Occult Talaromyces marneffei Infection Unveiled by the Novel Mp1p Antigen Detection Assay

Disseminated Talaromyces marneffei infection initially presenting as cutaneous and subcutaneous lesion in an HIV-Negative renal transplant recipient: a case report and literature review

BACKGROUND

The incidence of Talaromyces marneffei (T. marneffei) infection has increased in recent years with the development of organ transplantation and the widespread use of immunosuppressive agents. However, the lack of clinical suspicion leading to delay or misdiagnosis is an important reason for the high mortality rate in non-human immunodeficiency virus (HIV) and non-endemic population. Herein, we report a case of disseminated T. marneffei infection in a non-HIV and non-endemic recipient after renal transplant, who initially presented with skin rashes and subcutaneous nodules and developed gastrointestinal bleeding.

CASE PRESENTATION

We describe a 54-year-old renal transplantation recipient presented with scattered rashes, subcutaneous nodules and ulcerations on the head, face, abdomen, and right upper limb. The HIV antibody test was negative. The patient had no obvious symptoms such as fever, cough, etc. Histopathological result of the skin lesion sites showed chronic suppurative inflammation with a large number of fungal spores. Subsequent fungal culture suggested T. marneffei infection. Amphotericin B deoxycholate was given for antifungal treatment, and there was no deterioration in the parameters of liver and kidney function. Unfortunately, the patient was soon diagnosed with gastrointestinal bleeding, gastrointestinal perforation and acute peritonitis. Then he rapidly developed multiple organ dysfunction syndrome and abandoned treatment.

CONCLUSIONS

The risk of fatal gastrointestinal bleeding can be significantly increased in kidney transplant patients with T. marneffei infection because of the long-term side effects of post-transplant medications. Strengthening clinical awareness and using mNGS or mass spectrometry technologies to improve the detection rate and early diagnosis of T. marneffei are crucial for clinical treatment in non-HIV and non-endemic population.

Evaluation of the yeast phase-specific monoclonal antibody 4D1 and Galanthus nivalis agglutinin sandwich ELISA to detect Talaromyces marneffei antigen in human urine

Talaromyces (Penicillium) marneffei (TM) is an important, but neglected, thermally dimorphic fungus. It is the pathogenic cause of talaromycosis, which is strongly associated with the immunodeficiency state present in individuals with advanced HIV disease. The purpose of this study was to develop a sandwich enzyme-linked immunosorbent assay (sandwich ELISA) for the detection of T. marneffei cytoplasmic yeast antigen (TM CYA) in human urine. Monoclonal antibody (MAb) 4D1 specifically binds to TM CYA. Galanthus nivalis agglutinin (GNA), a mannose -binding lectin, recognizes and binds to mannose residues of TM CYA. For the sandwich ELISA, the microplate was coated with GNA as the capturing molecule for absorbing immune complexes of MAb 4D1-TM CYA. The MAb 4D1-GNA sandwich ELISA did not detect a cross-reaction with other antigens from other fungi or bacteria. Seventy-four urine samples from patients with blood culture -confirmed talaromycosis and 229 urine samples from people without talaromycosis residing in the endemic area were subjected to the MAb 4D1-GNA sandwich ELISA. At an optical density (OD) cutoff value of 0.356, the sensitivity was 89.19% [95% confidence interval (CI): 79.80% -95.22%]; the specificity was 98.69% (95% CI: 96.22% -99.73%). The diagnostic performance of the MAb 4D1-GNA sandwich ELISA was highly consistent with those of blood culture and the Platelia Aspergillus galactomannan (GM) ELISA kit. Collectively, the MAb 4D1-GNA sandwich ELISA is a promising technique for the rapid diagnosis of T. marneffei infection, which would facilitate the early treatment of patients with talaromycosis and it may be used to monitor treatment responses.

Environmentally Resilient Microfluidic Point-of-Care Immunoassay Enables Rapid Diagnosis of Talaromycosis

Point-of-care tests (POCTs) are increasingly being used in field settings, particularly outdoors. The performance of current POCTs─most commonly the lateral flow immunoassay─can be adversely affected by ambient temperature and humidity. We developed a self-contained immunoassay platform─the D4 POCT─that can be conducted at the POC by integrating all reagents in a capillary-driven passive microfluidic cassette that minimizes user intervention. The assay can be imaged and analyzed on a portable fluorescence reader─the D4Scope─and provide quantitative outputs. Here, we systematically investigated the resilience of our D4 POCT to varied temperature and humidity and to physiologically diverse human whole blood samples that span a wide range of physiological hematocrit (30-65%). For all conditions, we showed that the platform maintained high sensitivity (0.05-0.41 ng/mL limits of detection). The platform also demonstrated good accuracy in reporting true analyte concentration across environmental extremes when compared to the manually operated format of the same test to detect a model analyte─ovalbumin. Additionally, we engineered an improved version of the microfluidic cassette that improved the ease-of-use of the device and shortened the time-to-result. We implemented this new cassette to create a rapid diagnostic test to detect talaromycosis infection in patients with advanced HIV disease at the POC, demonstrating comparable sensitivity and specificity to the laboratory test for the disease.

An Overview of Diagnostic and Management Strategies for Talaromycosis, an Underrated Disease

Underrated and neglected, talaromycosis is a life-threatening fungal disease endemic to the tropical and subtropical regions of Asia. In China, it has been reported that talaromycosis mortality doubles from 24 to 50% when the diagnosis is delayed, and reaches 100% when the diagnosis is missed. Thus, the accurate diagnosis of talaromycosis is of utmost importance. Herein, in the first part of this article, we provide an extensive review of the diagnostic tools used thus far by physicians in the management of cases of talaromycosis. The challenges encountered and the perspectives which may aid in the discovery of more accurate and reliable diagnostic approaches are also discussed. In the second part of this review, we discuss the drugs used to prevent and treat T. marneffei infection. Alternative therapeutic options and potential drug resistance reported in the contemporary literature are also discussed. We aim to guide researchers towards the discovery of novel approaches to prevent, diagnose, and treat talaromycosis, and therefore improve the prognosis for those afflicted by this important disease.

An Overlooked and Underrated Endemic Mycosis-Talaromycosis and the Pathogenic Fungus Talaromyces marneffei

Talaromycosis is an invasive mycosis endemic in tropical and subtropical Asia and is caused by the pathogenic fungus Talaromyces marneffei. Approximately 17,300 cases of T. marneffei infection are diagnosed annually, and the reported mortality rate is extremely high (~1/3). Despite the devastating impact of talaromycosis on immunocompromised individuals, particularly HIV-positive persons, and the increase in reported occurrences in HIV-uninfected persons, diagnostic and therapeutic approaches for talaromycosis have received far too little attention worldwide. In 2021, scientists living in countries where talaromycosis is endemic raised a global demand for it to be recognized as a neglected tropical disease. Therefore, T. marneffei and the infectious disease induced by this fungus must be treated with concern. T. marneffei is a thermally dimorphic saprophytic fungus with a complicated mycological growth process that may produce various cell types in its life cycle, including conidia, hyphae, and yeast, all of which are associated with its pathogenicity. However, understanding of the pathogenic mechanism of T. marneffei has been limited until recently. To achieve a holistic view of T. marneffei and talaromycosis, the current knowledge about talaromycosis and research breakthroughs regarding T. marneffei growth biology are discussed in this review, along with the interaction of the fungus with environmental stimuli and the host immune response to fungal infection. Importantly, the future research directions required for understanding this serious infection and its causative pathogenic fungus are also emphasized to identify solutions that will alleviate the suffering of susceptible individuals worldwide.

Clinical performance of metagenomic next-generation sequencing for the rapid diagnosis of talaromycosis in HIV-infected patients

Background

Talaromycosis is an invasive endemic mycosis caused by the dimorphic fungus Talaromyces marneffei (T. marneffei, TM). It mainly affects immunodeficient patients, especially HIV-infected individuals, which causes significant morbidity and mortality. Culture-based diagnosis takes a long turnaround time with low sensitivity, leading to treatment delay. In this study, we aimed to evaluate the performance of Metagenomic Next-Generation Sequencing (mNGS) for the rapid diagnosis of talaromycosis in HIV-infected patients.

Methods

Retrospectively analysis was conducted in HIV-infected cases at Changsha First Hospital (China) from January 2021 to March 2022. Patients who underwent routine microbiological examination and mNGS testing in parallel were enrolled. The clinical final diagnosis was used as a reference standard, and cases were classified into the TM group (60 cases) and the non-TM group (148 cases). The clinical performances of mNGS were compared with culture and serum Galactomannan (GM). The mixed infections detected by mNGS were analyzed. The impact of mNGS detection on treatment was also investigated.

Results

The sensitivity of mNGS test reached 98.3% (95% CI, 89.8-99.9), which was significantly higher than culture (66.7% [95% CI, 53.2-77.9], P < 0.001) and serum GM (83.3% [95% CI, 71.0-91.2], P < 0.05). The specificity of 98.6% (95% CI, 94.7-99.7) was similar to culture (100.0% [95% CI, 96.8-100.0], P = 0.156), and superior to serum GM (91.9% [95% CI, 85.9-95.5], P < 0.05). In bronchoalveolar lavage fluid (BALF) samples, the positive rate of mNGS was 97.6%, which was significantly higher than culture (28.6%, P <0.001). mNGS has excellent performance in the identification of mixed infection in TM group patients. Cytomegalovirus, Epstein-Barr virus and Pneumocystis jirovecii were the most common concurrent pathogens. In summary, 60.0% (36/60) patients were added or adjusted to antimicrobial therapy after mNGS test.

Conclusion

mNGS is a powerful technique with high specificity and sensitivity for the rapid diagnosis of talaromycosis. mNGS of BALF samples may be a good option for early identification of T. marneffei in HIV-infected individuals with manifestations of infection. Moreover, mNGS shows excellent performance in mixed infection, which benefits timely treatment and potential mortality reduction.

Clinical features of patients with talaromycosis marneffei and microbiological characteristics of the causative strains

BACKGROUND

Talaromyces marneffei (T. marneffei) is a temperature-dependent dimorphic fungus that is mainly prevalent in Southeast Asia and South China and often causes disseminated life-threatening infections. This study aimed to investigate the clinical features and improve the early diagnosis of talaromycosis marneffei in nonendemic areas.

METHODS

We retrospectively analyzed the medical records of six cases of T. marneffei infection. We describe the clinical manifestations, laboratory tests, and imaging manifestations of the six patients.

RESULTS

Talaromyces marneffei infection was confirmed by sputum culture, blood culture, tissue biopsy, and metagenomic next-generation sequencing (mNGS). In this study, there were five disseminated-type patients and two HIV patients. One patient died within 24 h, and the others demonstrated considerable improvement after definitive diagnosis.

CONCLUSIONS

Due to the lack of significant clinical presentations of talaromycosis marneffei, many cases may be easily misdiagnosed in nonendemic areas. It is particularly important to analyze the imaging manifestations and laboratory findings of infected patients. With the rapid development of molecular biology, mNGS may be a rapid and effective diagnostic method.

Noninvasive Testing and Surrogate Markers in Invasive Fungal Diseases

Invasive fungal infections continue to increase as at-risk populations expand. The high associated morbidity and mortality with fungal diseases mandate the continued investigation of novel antifungal agents and diagnostic strategies that include surrogate biomarkers. Biologic markers of disease are useful prognostic indicators during clinical care, and their use in place of traditional survival end points may allow for more rapid conduct of clinical trials requiring fewer participants, decreased trial expense, and limited need for long-term follow-up. A number of fungal biomarkers have been developed and extensively evaluated in prospective clinical trials and small series. We examine the evidence for these surrogate biomarkers in this review and provide recommendations for clinicians and regulatory authorities.

Talaromyces marneffei Mp1p Antigen Detection may Play an Important Role in the Early Diagnosis of Talaromycosis in Patients with Acquired Immunodeficiency Syndrome

Talaromycosis is a life-threatening fungal disease commonly seen in patients with acquired immunodeficiency syndrome (AIDS), which is endemic in Southern China and Southeast countries. The diagnostic methods available for talaromycosis are relatively time-consuming and yield a high mortality. Therefore, early diagnosis of talaromycosis is extremely important. We aimed to determine a potential method for assisting in its early diagnosis. A total of 283 patients with AIDS admitted to our hospital were prospectively included in this cross-sectional study and divided into those with Talaromyces marneffei (TSM group, n = 93) and those without Talaromyces marneffei (non-TSM group, n = 190). The diagnostic accuracy of the Mp1p enzyme immunoassay (EIA), galactomannan (GM) assay, and blood culture performed within 3 days of hospitalisation were evaluated, using talaromycosis confirmed by culture and/or pathology as the gold standard. The positivity rates in the Mp1p EIA, GM assay, and blood culture were 72%, 64.5%, and 81.7%, respectively, in the TSM group. The sensitivity, specificity, and positive and negative predictive values of the Mp1p EIA were 72.0% (67/93), 96.8% (184/190), 91.8% (67/73), and 87.6% (184/210), respectively. The Mp1p EIA showed a substantial agreement with the gold standard (kappa: 0.729) and superiority to the GM assay (kappa: 0.603); it also showed a superior diagnostic accuracy in the patients with CD4+ counts of < 50 cells/µL compared to those with CD4+ counts ranged from 50–100 cells/µL. The Mp1p EIA has the advantage of assisting in the early diagnosis of talaromycosis in patients with AIDS, especially those with low CD4+ counts.

A global call for talaromycosis to be recognised as a neglected tropical disease

Talaromycosis (penicilliosis) is an invasive mycosis that is endemic in tropical and subtropical Asia. Talaromycosis primarily affects individuals with advanced HIV disease and other immunosuppressive conditions, and the disease disproportionally affects people in low-income and middle-income countries, particularly agricultural workers in rural areas during their most economically productive years. Approximately 17 300 talaromycosis cases and 4900 associated deaths occur annually. Talaromycosis is highly associated with the tropical monsoon season, when flooding and cyclones can exacerbate the poverty-inducing potential of the disease. Talaromycosis can present as localised or disseminated disease, the latter causing cutaneous lesions that are disfiguring and stigmatising. Despite up to a third of diagnosed cases resulting in death, talaromycosis has received little attention and investment from regional and global funders, policy makers, researchers, and industry. Diagnostic and treatment modalities remain extremely insufficient, however control of talaromycosis is feasible with known public health strategies. This Viewpoint is a global call for talaromycosis to be recognised as a neglected tropical disease to alleviate its impact on susceptible populations.

Serum Sphingolipids Aiding the Diagnosis of Adult HIV-Negative Patients with Talaromyces marneffei Infection

Increasing attention has been directed to Talaromyces marneffei (T. marneffei) infection in HIV-negative patients due to its high mortality rate. However, nonspecific symptoms and biological characteristics similar to those of other common pathogenic fungi complicate the rapid and accurate diagnosis of T. marneffei infection. Sphingolipids (SPLs) are bioactive lipids involved in the regulation of various physiological and pathological processes and have been identified as serum biomarkers for several diseases. This study employed a sphingolipidomic approach established in our previous work to explore the use of serum SPLs in the diagnosis of HIV-negative patients with T. marneffei infection. Additional clinical cohorts of patients infected with other microorganisms were also recruited. We found that sphinganine (Sa) (d16:0) exhibited obvious depletion after infection; moreover, its level in patients with T. marneffei infection was significantly lower than that in patients infected with other microorganisms. Therefore, Sa (d16:0) was considered a specific diagnostic biomarker for T. marneffei infection, and 302.71 nM was selected as the optimal cutoff value with a diagnostic sensitivity of 87.5% and specificity of 100%. These results suggested that determination of serum Sa (d16:0) levels can be used as a new alternative tool for the rapid diagnosis of T. marneffei infection in HIV-negative patients.

Diagnosis of Pulmonary Infections Due to Endemic Fungi

Endemic mycoses including Histoplasma, Blastomyces, Coccidioides, Paracoccidioides, and Talaromyces are dimorphic fungi that can cause a variety of clinical manifestations, including respiratory infections. Their pulmonary presentations are variable, and diagnosis is often delayed as they can mimic other infectious and non-infectious causes of pulmonary disease. Delay in diagnosis can lead to unnecessary antibiotic use, repeat hospitalizations, and increased morbidity and mortality. The diagnosis of endemic fungal pulmonary infections often relies on multiple diagnostic tests including culture, tissue histopathology, antigen assays, and antibody assays. Due to the increased use of immunosuppressive agents and the widening geographic ranges where these infections are being found, the prevalence of endemic fungal infections is increasing. Physicians need to be aware of the clinical manifestations of pulmonary infections due to endemic fungal in order to ensure that the proper diagnostic work up is obtained promptly. A high index of suspicion is particularly important in patients with suspected pulmonary infections who have failed to improve despite antibiotics in the appropriate setting. We present a review diagnostic testing for pulmonary infections due to endemic mycoses.