Cross-reactivity of Nocardia spp. in the fungal (1-3)-β-d-glucan assay performed on cerebral spinal fluid

ß-D-Glucan Assay in the Cerebrospinal Fluid for the Diagnosis of Non-cryptococcal Fungal Infection of the Central Nervous System: A Retrospective Multicentric Analysis and a Comprehensive Review of the Literature

BACKGROUND

Except for cryptococcosis, fungal infection of the central nervous system (FI-CNS) is a rare but severe complication. Clinical and radiological signs are non-specific, and the value of conventional mycological diagnosis is very low. This study aimed to assess the value of β1,3-D-glucan (BDG) detection in the cerebrospinal fluid (CSF) of non-neonatal non-cryptococcosis patients.

METHODS

Cases associated with BDG assay in the CSF performed in 3 French University Hospitals over 5 years were included. Clinical, radiological, and mycological results were used to classify the episodes as proven/highly probable, probable, excluded, and unclassified FI-CNS. Sensitivity and specificity were compared to that calculated from an exhaustive review of the literature.

RESULTS

In total, 228 episodes consisting of 4, 7, 177, and 40 proven/highly probable, probable, excluded, and unclassified FI-CNS, respectively, were analysed. The sensitivity of BDG assay in CSF to diagnose proven/highly probable/probable FI-CNS ranged from 72.7% [95% confidence interval {CI}: 43.4%‒90.2%] to 100% [95% CI: 51%‒100%] in our study and was 82% in the literature. For the first time, specificity could be calculated over a large panel of pertinent controls and was found at 81.8% [95% CI: 75.3%‒86.8%]. Bacterial neurologic infections were associated with several false positive results.

CONCLUSIONS

Despite its sub-optimal performance, BDG assay in the CSF should be added to the diagnostic armamentarium for FI-CNS.

Nocardiosis and elevated beta-d-glucan in solid organ transplant recipients

Beta-D-glucan (BDG) testing can expedite the diagnosis of invasive fungal infections in immunocompromised hosts. Elevated BDG levels have been reported in both in-vitro studies assessing cross-reactivity with Nocardia spp. and published cases of patients with nocardiosis, but there is little data on this association in solid organ transplantation (SOT) recipients. To explore this association, we conducted a case series of SOT recipients with culture-proven nocardiosis and BDG testing who received their care at our institution between 2016 and 2021. We found thirteen cases of nocardiosis in SOT recipients, of which three cases met our case definition of an elevated BDG. Their clinical courses are detailed in the present report. We found that BDG may be elevated in SOT with nocardiosis with no identified cause of false positive BDG, though a causal association cannot be determined. Future prospective studies that better evaluate the association between nocardiosis and BDG are warranted, as are studies that better characterize the possible variability in reactivity amongst Nocardia spp.

Specificity Influences in (1→3)-β-d-Glucan-Supported Diagnosis of Invasive Fungal Disease

(1→3)-β-glucan (BDG) testing as an adjunct in the diagnosis of invasive fungal disease (IFD) has been in use for nearly three decades. While BDG has a very high negative predictive value in this setting, diagnostic false positives may occur, limiting specificity and positive predictive value. Although results may be diagnostically false positive, they are analytically correct, due to the presence of BDG in the circulation. This review surveys the non-IFD causes of elevated circulating BDG. These are in the main, iatrogenic patient contamination through the use of BDG-containing medical devices and parenterally-delivered materials as well as translocation of intestinal luminal BDG due to mucosal barrier injury. Additionally, infection with Nocardia sp. may also contribute to elevated circulating BDG. Knowledge of the factors which may contribute to such non-IFD-related test results can improve the planning and interpretation of BDG assays and permit investigational strategies, such as serial sampling and BDG clearance evaluation, to assess the likelihood of contamination and improve patient care.

Elevated serum βglucan levels in cavitary pulmonary nocardiosis

An 86-year-old woman with Borrmann type III colorectal cancer (Union for International Cancer Control pT4aN2bM1c, pStage IVc) had received dexamethasone for the last 6 months as palliative care. She presented with a low-grade fever, chest pain and cough. Chest radiography on admission showed cavities and consolidations bilaterally in the upper lobes. A blood examination on admission revealed highly elevated serum β-d-glucan levels. The diagnosis by bronchoscopy was pulmonary nocardiosis. With trimethoprim/sulfamethoxazole and imipenem/cilastatin, the β-d-glucan levels were decreased, and chest X-ray showed improvement after 1 month. β-d-glucan is known to be a biomarker of fungal infection. It is possible that β-d-glucan levels also indicate a pulmonary infection by Nocardia.

[Cerebral and pulmonary nocardiosis to Nocardia abscessus in an immunocompetent Algerian patient]

Nocardial brain abscess is often occurring in immunocompromised patients. It is uncommon in immunocompetent individuals. Here, the authors describe a case of cerebral and pulmonary nocardiosis mimicking a metastatic tumor in an apparently health 40-year-old Algerian male. The patient presented multiple brain abscess revealed by inaugural epileptic seizure. He was afebrile and presented with left hemiparesis. Staging imaging showed a nodular lung lesion in the apical segment of the right lower lobe. The patient underwent double craniotomy for resection of the lesion. Culture of the resected specimen isolated Nocardia abscessus. The patient was initially started on intravenous trimethoprim-sulfamethoxazole and intravenous amikacine. He was switched to oral trimethoprim-sulfamethoxazole. He finished seven months of antibiotic therapy with a good clinical response. Imaging revealed reduction in the brain abscess and a complete resolution of the lung lesion. Cotrimoxazole was stopped after twelve months of therapy. After two years, the health status of our patient improves day after day. He is however regularly under medical supervision for control exams.

Nocardia infections in solid organ and hematopoietic stem cell transplant recipients

PURPOSE OF REVIEW

Nocardia spp. is a gram-positive bacteria that may cause infections in humans. Nocardiosis has been described since the early years of transplantation. This review aims to provide an overview of present knowledge regarding posttransplant nocardiosis, with a focus on recent findings.

RECENT FINDINGS

Nocardiosis is not rare among transplant recipients, especially after thoracic transplantation and/or in case of intense immunosuppressive regimen or use of tacrolimus. Low-dose cotrimoxazole is not effective to prevent nocardiosis. Although lung is the most common site of infection, more than 40% of organ transplant patients have a disseminated infection. As central nervous system involvement is frequent (about 1/3 of the patients) and possibly asymptomatic, brain imaging is mandatory. Diagnosis relies on direct examination and culture; molecular species identification is useful to guide treatment. Although cotrimoxazole is the drug for which we have the strongest clinical experience, other antibiotics such as linezolid, parenteral cephalosporins, carbapenems, and amikacin can be used to treat nocardiosis. Although treatment duration has historically been set to at least 6 months, shorter durations (<120 days) seem associated with a good outcome in selected patients.

SUMMARY

Physicians in charge of transplant patients should be aware of nocardiosis. Diagnosis and management of transplant recipients with nocardiosis require a multidisciplinary approach.

Use of 1,3-β-D-glucan in invasive fungal diseases in hematology patients

INTRODUCTION

Invasive fungal diseases (IFD) remain a leading cause of morbidity and mortality in hematology patients. Within a diagnostic-driven approach, the use of the serum (1,3)-ß-D-glucan (BDG) test represents a valid tool for the early diagnosis and treatment of IFD. Areas covered: The available literature on the use of BDG in hematology patients was systematically retrieved. Then, it was reviewed and discussed, to identify key issues pertaining to a clinically-oriented narrative presentation of the topic. Expert commentary: The use of BDG in hematology patients at risk for invasive aspergillosis (IA) is secondary to the use of galactomannan. However, since BDG is not specific for IA, it offers an advantage of diagnosing also other IFD, such as candidiasis and pneumocystosis. The limitations of BDG include high costs and lower sensitivity in hematology patients compared to other cohorts. The risk of false positive results is possibly lower in real life than in theory, since glucan-free equipment is available and modern dialysis membranes and blood products usually do not release BDG. Thus, in experienced hands and selected clinical situations, BDG is a useful diagnostic tool, particularly due to short turnover time to results and versatility in diagnosing different IFD.

Elevated Serum Beta-D-Glucan with Pseudomonas, Aspergillus, and a Partially Acid-Fast Organism in Respiratory Cultures: A Case of Hickam's Dictum Over Occam's Razor

We describe a case of a man with ectopic Cushing's syndrome, elevated serum beta-D-glucan, and respiratory cultures with Pseudomonas, Aspergillus, and a partially acid-fast organism. Our case highlights challenges in diagnosis and management of coinfection in an immunocompromised host.

Detection of high serum levels of β-D-Glucan in disseminated nocardial infection: a case report

Background

β-D-glucan (BDG) is a helpful diagnostic marker for many invasive fungal infections, but not for nocardiosis. Here, we reported the first case of nocardial infection with high serum level of BDG.

Case presentation

A 73-year-old man was hospitalized because of fever, headache, and appetite loss after 10 months of steroid and immunosuppressive therapy for cryptogenic organizing pneumonia. With a diagnosis of bacterial pneumonia, treatment with ampicillin/sulbactam was initiated. There was improvement on chest radiograph, but fever persisted. Further work-up revealed multiple brain abscesses on cranial magnetic resonance imaging (MRI). Serum galactomannan and BDG were elevated at 0.6 index and 94.7 pg/ml, respectively. Voriconazole was initiated for presumed aspergillus brain abscess. However, fever persisted and consciousness level deteriorated. Drainage of brain abscess was performed; based on the Gram stain and Kinyoun acid-fast stain, disseminated nocardiosis was diagnosed. Voriconazole was then shifter to trimethoprim/sulfamethoxazole. The presence of Nocardia farcinica was confirmed by the 16S rRNA gene sequence. Treatment course was continued; BDG level normalized after 1 month and cranial MRI showed almost complete improvement after 2 months.

Conclusion

BDG assay is widely used to diagnose invasive fungal infection; therefore, clinicians should be aware that Nocardia species may show cross-reactivity with BDG assay on serum.

Detection of (1→3)-β-d-Glucan in Eumycetoma Patients

Mycetoma can be caused by bacteria (actinomycetoma) or fungi (eumycetoma). Here, we demonstrated in 45 eumycetoma patients, 30 actinomycetoma patients, and 30 healthy controls that (1→3)-β-d-glucan detection in serum cannot reliably be used to discriminate between the two types of mycetoma.

Prospective Evaluation of Serum β-Glucan Testing in Patients With Probable or Proven Fungal Diseases

We evaluated the positivity of (1-3)-β-D-glucan, a serum marker of invasive fungal diseases (IFD), at diagnosis and during treatment. (1-3)-β-D-Glucan may not be an early marker but could prove useful for diagnosis of chronic IFD.

Background. Early diagnosis and treatment are crucial in invasive fungal diseases (IFD). Serum (1-3)-β-d-glucan (BG) is believed to be an early IFD marker, but its diagnostic performance has been ambiguous, with insufficient data regarding sensitivity at the time of IFD diagnosis (TOD) and according to outcome. Whether its clinical utility is equivalent for all types of IFD remains unknown.

Methods. We included 143 patients with proven or probable IFD (49 invasive candidiasis, 45 invasive aspergillosis [IA], and 49 rare IFD) and analyzed serum BG (Fungitell) at TOD and during treatment.

Results. (1-3)-β-d-glucan was undetectable at TOD in 36% and 48% of patients with candidemia and IA, respectively; there was no correlation between negative BG results at TOD and patients' characteristics, localization of infection, or prior antifungal use. Nevertheless, patients with candidemia due to Candida albicans were more likely to test positive for BG at TOD (odds ratio = 25.4, P = .01) than patients infected with other Candida species. In 70% of the patients with a follow-up, BG negativation occurred in >1 month for candidemia and >3 months for IA. A slower BG decrease in patients with candidemia was associated with deep-seated localizations (P = .04). Thirty-nine percent of patients with rare IFD had undetectable BG at TOD; nonetheless, all patients with chronic subcutaneous IFD tested positive at TOD.

Conclusions. Undetectable serum BG does not rule out an early IFD, when the clinical suspicion is high. After IFD diagnostic, kinetics of serum BG are difficult to relate to clinical outcome.