Difficulty in diagnosing chronic meningitis caused by capsule-deficient Cryptococcus neoformans

Capsule-Deficient Cryptococcal Meningitis: A Diagnostic Conundrum

Cryptococcosis is a serious systemic mycosis. Its incidence has escalated in the past four decades. Cryptococcus neoformans causes localized or disseminated infection in immunocompromised and immunocompetent patients. The capsulated form is commonly encountered which can be diagnosed on an India ink preparation or antigen detection. However, the noncapsulated forms are very rare and require a high index of suspicion for correct diagnosis. Herein, we present a case of cryptococcal meningitis due to a noncapsulated strain in an apparently immunocompetent patient with no proven immunodeficiencies along with review of world literature. Such cases are a diagnostic challenge for the clinician as well as microbiologist.

Hidden in plain sight: urinary Cryptococcus neoformans missed by routine diagnostics in a patient with acute leukemia

Cryptococcuria is a rare manifestation of localized cryptococcal disease. We present a case of Cryptococcus neoformans urinary tract infection in an immunocompromised host missed by routine laboratory workup. The patient had negative blood cultures, a negative serum cryptococcal antigen (CrAg), and “non-Candida yeast” growing in urine culture that was initially dismissed as non-pathogenic. The diagnosis was ultimately made by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) from a repeat urine culture after transfer to a tertiary care center. Cryptococcus should be considered in the differential of refractory urinary tract infections growing non-Candida yeast.

Molecular identification of Cryptococcus gattii from cerebrospinal fluid using single-cell sequencing: A case study

A 31-year-old man presented with cryptococcal meningitis (CM) without typical clinical characteristics, but with abnormal walking, difficult leg lifting and frequent falling. He was admitted to Peking Union Medical College Hospital. After multiple tests failed to identify the pathogen, single-cell sequencing (scS) was used to test the cerebrospinal fluid (CSF). Comparing the sequence obtained from single-cell sequencing with the reference database, it was found that the infection was caused by Cryptococcus gattii sensu stricto (AFLP4/VGI genotype). Cryptococcus is difficult to cultivate from complex body fluids. The etiological agent of this patient was identified and the patient was treated. This is the first case in which scS was used to detect and identify fungal pathogen after conventional testing failed to identify the cause of the disease. This report demonstrates that the scS approach can be used to generate fungal genome sequences directly from the CSF of a CM patient. The scS technology could become a powerful tool to precise detect microscopically visible but uncultured pathogens in clinical samples.

Apparent performance of metagenomic next-generation sequencing in the diagnosis of cryptococcal meningitis: a descriptive study

INTRODUCTION

In recent years, metagenomic next-generation sequencing (mNGS) has become widely used in medical microbiology to detect pathogen infection.

AIM

We aimed to assess the diagnostic performance of mNGS of cerebrospinal fluid (CSF) for prediction of cryptococcal meningitis (CM).

METHODOLOGY

A comparative evaluation of mNGS (performed on CSF samples) and conventional methods, including India ink staining, culture for fungi and cryptococcal-antigen (CrAg) detection by enzyme immunoassay, was performed on 12 consecutive non-HIV-infected patients with chronic or subacute CM.

RESULTS

India ink staining and culture of the CSF were positive for Cryptococcus in 83.33 % (10/12) of the samples; 100 % (11/11) were positive via CrAg EIA. The mNGS results of the CSF identified DNA sequences corresponding to Cryptococcus in 75 % of samples (9/12). However, the DNA of both C. neoformans s.l. and C. gattii s.l. was detected concurrently in 33.33 % (4/12).

CONCLUSION

mNGS is helpful for identifying Cryptococcus species. The application of mNGS, together with India ink staining, culture methods, and CrAg, may significantly improve the diagnostic precision in CM, thereby informing choice of appropriate antifungal treatment courses.

Diagnostic Challenges of Cryptococcus neoformans in an Immunocompetent Individual Masquerading as Chronic Hydrocephalus

Cryptococcus neoformans can cause disseminated meningoencephalitis and evade immunosurveillance with expression of a major virulence factor, the polysaccharide capsule. Direct diagnostic assays often rely on the presence of the cryptococcal glucuronoxylomannan capsular antigen (CrAg) or visualization of the capsule. Strain specific phenotypic traits and environmental conditions influence differences in expression that can thereby compromise detection and timely diagnosis. Immunocompetent hosts may manifest clinical signs and symptoms indolently, often expanding the differential and delaying appropriate treatment and diagnosis. We describe a 63-year-old man who presented with a progressive four-year history of ambulatory dysfunction, headache, and communicating hydrocephalus. Serial lumbar punctures (LPs) revealed elevated protein (153–300 mg/dL), hypoglycorrhachia (19–47 mg/dL), lymphocytic pleocytosis (89–95% lymphocyte, WBC 67–303 mg/dL, and RBC 34–108 mg/dL), and normal opening pressure (13–16 cm H₂O). Two different cerebrospinal fluid (CSF) CrAg assays were negative. A large volume CSF fungal culture grew unencapsulated C. neoformans. He was initiated on induction therapy with amphotericin B plus flucytosine and consolidation/maintenance therapy with flucytosine, but he died following discharge due to complications. Elevated levels of CSF Th1 cytokines and decreased IL6 may have affected the virulence and detection of the pathogen.

Pitfalls in Serological Diagnosis of Cryptococcus gattii Infections

The detection of cryptococcal antigen by latex agglutination tests (LATs), enzyme-linked immunoassays (ELISA), or lateral flow assay (LFA) is an important tool for diagnosis of a Cryptococcus infection. Cerebrospinal fluid and/or serum samples of 10 patients with cryptococcosis due to Cryptococcus gattii or a hybrid of Cryptococcus neoformans and C. gattii were examined by three LATs (the IMMY Latex-Crypto(®) test, the Pastorex(TM) Crypto Plus, and the Remel Cryptococcus Antigen Test Kit) and the LFA made by Immuno-Mycologics. LATs based on monoclonal antibodies (mAbs) like the Pastorex(TM) Crypto Plus or the Remel Cryptococcus Antigen Test Kit turned out to have an insufficient sensitivity to detect four out of 10 C. gattii infections, including one infection by a hybrid between C. gattii and C. neoformans. Reflecting the ongoing expansion of C. gattii in geographical zones outside of tropical and subtropical areas like Mediterranean countries, Vancouver Island (British Columbia, Canada) and the Pacific Northwest region (USA), these findings are alarming because of the risk of delayed diagnosis of infections caused by C. gattii. Therefore, the preliminary serological screening for cryptococcal antigen in the case of a suspected Cryptococcus infection should be performed by using an assay with a broad range specificity and sensitivity for C. neoformans and C. gattii, including their hybrids.

Neuroinvasive cryptococcosis in an immunocompetent patient with a negative spinal fluid cryptococcus antigen

58-year-old man presented with headache, nausea, vomiting, and gait disturbance. Brain MRI showed meningeal enhancement and herniation. Serum Cryptococcus antigen was positive but spinal fluid antigen and cultures were negative. A cerebellar biopsy revealed nonencapsulated Cryptococcus. He completed antifungal therapy. Serum Cryptococcus antigen titer decreased. He had a full neurological recovery.

Central nervous system infections in cancer patients and hematopoietic stem cell transplant recipients

Central nervous system (CNS) infections in cancer patients present a diagnostic and therapeutic challenge for clinicians. While CNS infections are not frequent complications of cancer, its therapies, or hematopoietic stem cell transplantation, the importance of CNS infections lies in their propensity to result in profound morbidity and substantial mortality in this vulnerable patient population. With an expanding population of patients with malignant disease undergoing more potent and aggressive therapies and with the advent of newer immunomodulatory agents, the incidence of CNS infectious complications is likely to rise. This chapter will summarize the clinical and diagnostic evaluation of potential infections of the CNS in these patients and will discuss particular pathogens of interest with regard to this at-risk patient population.

A multi-target real-time PCR assay for rapid identification of meningitis-associated microorganisms

A central nervous system (CNS) infection, such as meningitis, is a serious and life-threatening condition. Bacterial meningitis can be severe and may result in brain damage, disability or even death. Rapid diagnosis of CNS infections and identification of the pathogenic microorganisms are needed to improve the patient outcome. Bacterial culture of a patient's cerebrospinal fluid (CSF) is currently considered the "gold standard" for diagnosing bacterial meningitis. From the CSF cultures researchers can assess the in vitro susceptibility of the causative microorganism to determine the best antibiotic treatment. However, many of the culture assays, such as microscopy and the latex agglutination test are not sensitive. To enhance pathogen detection in CSF samples we developed a multi-target real-time PCR assay that can rapidly identify six different microorganisms: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Streptococcus agalactiae, Listeria monocytogenes and Cryptococcus neoformans. In this study we applied this PCR analysis to 296 CSF samples from patients who were suspected of having meningitis. Of the 296 samples that were examined, 59 samples were positive according to the CSF culture and/or molecular assays. Forty-six CSF samples were positive for both the CSF culture and our real-time PCR assay, while 13 samples were positive for the real-time PCR but negative for the traditional assays. This discrepancy may have been caused by the fact that these samples were collected from 23 patients who were treated with antimicrobials before CSF sampling.

Significance of antibody detection in the diagnosis of cryptococcal meningitis

Cryptococcus neoformans is the causative agent of Cryptococcosis, a chronic and life-threatening infection common in AIDS patients. Sonicated proteins of cryptococci were reported to contain antigenic properties. In the present study antigens are prepared from cryptococcal culture filtrate and by sonication. Secretory antigens are prepared by precipitation of culture filtrate using saturated ammonium sulfate followed by dialysis. Prepared antigens are tested for the presence of antibodies in the CSF samples of cryptococcal meningitis cases by ELISA. Comparison is made between India ink staining, latex antigen test, and the antibodies to the sonicated and secretory antigens. The results indicate that although antigen could be detected in the majority of samples, antibody could also be detected to the extent of 80-85%. It is interesting to note that some samples that were negative for India ink staining also showed high antibody responses. Hence, antibody detection could be a valuable marker in association with India ink staining for the early diagnosis of the cryptococcal infection. This test may also counter false positivity encountered in latex antigen test. Antibody detection assay would be a viable alternative, which has 83% sensitivity and 100% specificity. Thus the presently described test aids in immunodiagnosis of cryptococcal infection.

Treatment of indolent, nonencapsulated cryptococcal meningitis associated with hydrocephalus

Infection with cryptococcal meningitis is uncommon in immunocompetent patients. The major virulence factor is the polysaccharide capsule, while nonencapsulated mutants are generally considered nonpathogenic. The authors present a case of hydrocephalus caused by meningitis from an indolent, nonencapsulated Cryptococcus sp. requiring placement and multiple revisions of a ventriculoperitoneal shunt (VPS). The patient presented with progressively worsening occipital headaches. Computed tomography and magnetic resonance imaging showed significant hydrocephalus with no apparent cause. Her symptoms initially resolved after placement of a VPS, but returned four months later. Cultures of the shunt tubing and cerebrospinal fluid (CSF) showed no bacterial infection. When the symptoms failed to resolve, CSF fungal culture revealed Cryptococcus-like yeast, although the organisms were nonencapsulated, and the cryptococcal antigen was negative. After antibiotic therapy, the symptoms resolved. The unusual clinical presentation delayed the diagnosis, highlighting the importance of understanding the detection, diagnosis, and treatment of meningeal infections caused by C. neoformans.

Coccidioides, cryptococcus, or blastomyces? A diagnostic dilemma encountered during frozen section evaluation

Intraoperative consultation via frozen section is an important part of modern day surgical pathology. Recognizing fungi in tissues on frozen and permanent sections is not always a simple task, and correctly identifying the agent can be a significant challenge, even for experienced microscopists. We present a case of a 17-year-old boy with chronic osteomyelitis involving the right proximal ulna. During an irrigation and debridement operation, a frozen section was sent to surgical pathology for evaluation. A limited patient history coupled with sparse organisms present in the frozen section led to the diagnosis of fungal osteomyelitis, favor Coccidioides . Follow-up permanent sections with special staining and successful fungal culture clarified the causal agent to be Blastomyces dermatitidis . The role of frozen sections is not to perfectly speciate the fungal pathogen but to describe the morphology and infectious process and provide a differential diagnosis of the candidate fungi. The importance of intraoperative culture in infectious cases cannot be understated, and it is the responsibility of pathologists to inform surgeons that tissue is needed for culture. A brief overview of Blastomyces , including histopathologic features and key microscopic differences from Coccidioides and Cryptococcus , is discussed.

Comparison of real-time florescence quantitative PCR measurements of VAD1 mRNA with three conventional methods in diagnosis and follow-up treatment of Cryptococcus neoformans infection

This study was to develop a real-time florescence quantitative PCR (RT-FQ-PCR) assay to measure virulence-associated DEAD-box RNA helicase (VAD1) mRNA from Cryptococcus neoformans and evaluate its potential use in diagnosis and follow-up treatment of C. neoformans meningitis (CNM). Cryptococcus neoformans was detected using RT-FQ-PCR, ink staining, fungal culturing and C. neoformans antigen detection in CNM compared with a normal control. VAD1 mRNA was measured in both acute and stable CNM patients. The sensitivity of RT-FQ-PCR (96%) is higher than ink staining (72%) and culture culturing (64%) (P<0.05, P<0.05 respectively), but its sensitivity is the same as antigen detection (96%, P>0.05). The levels of VAD1 mRNA in the acute and stable phase of a C. neoformans infection are 3.042±0.906 and 2.187±0.665 respectively (P<0.01). The levels of VAD1 mRNA are correlated to the numbers of C. neoformans, intracranial pressure and glucose concentration in cerebrospinal fluid (CSF; P<0.01, P<0.01 and P<0.05 respectively). The levels of expression of VAD1 mRNA in the group of patients who received an AmB/5-FC/FZC drug regimen decreased more than in patients taking a 5-FC/AmB or 5-FC/FCZ drug combination. Quantitative measurements of VAD1 mRNA are valuable and reliable in diagnosing C. neoformans infection and evaluating a therapy response.

Difficulty diagnosing chronic cryptococcal meningitis in idiopathic CD4+ lymphocytopenia

A 64-year-old man with idiopathic CD4(+) lymphocytopenia developed cognitive impairment and gait ataxia with isolated obstructive hydrocephalus, which was fatal. Cerebrospinal fluid showed mild pleocytosis, but the etiology was not revealed by extensive analysis. At autopsy, inflammatory cells, CD8(+) lymphocytes and abundant macrophages but not CD4(+) lymphocytes were infiltrating the meninges at the base of the brain. Electron microscopy demonstrated that inflammation was caused by Cryptococcus neoformans, which was localized exclusively within macrophages, where it grew with budding. Our study suggests that, in idiopathic CD4(+) lymphocytopenia, macrophages can efficiently phagocytize but inefficiently digest C. neoformans, thus representing a vehicle of chronic intracellular infection.

Unusual morphologies of Cryptococcus spp. in tissue specimens: report of 10 cases

Ten cases of cryptococcosis due to unusual microscopic forms of Cryptococcus sp. observed over a twenty-eight year period (1981-2009) are presented. The most important clinicopathological and laboratory data are tabulated. The uncommon forms of cryptococcal cells given are: structures resembling germ tube (one case), chains of budding yeasts (one case), pseudohyphae (two cases) and nonencapsulated yeast-like organisms (eight cases). The diagnosis was based on the histopathological findings. The causative organism was isolated and identified in seven cases; five were due to C. neoformans, and two to C. gattii. In addition, the importance of using staining histochemical techniques - Grocott's silver stain (GMS), Mayer's mucicarmine stain (MM) and Fontana-Masson stain (FM) - in the diagnosis of cryptococcosis is argued.

Histopathology, serology and cultures in the diagnosis of cryptococcosis

Cryptococcosis is one of the most common opportunistic fungal infections in patients with acquired immunodeficiency syndrome (AIDS). We report 13 cases of cryptococcal infection based on histopathology, serology and cultures. Epidemiological analysis, histochemical techniques of hematoxilin and eosin (HE) and Grocot's silver (GMS), as well special histochemical techniques such as Mayer's mucicarmine (MM) and Fontana-Masson (FM), cryptococcal antigen test (CrAg) and isolation on fungal media: Sabouraud's (SAB), brain-heart infusion agar (BHI) and canavanine-glycine-bromothymol blue (CGB) agar were analyzed. Unsatisfactory staining results by MM stain associated to negative titers by CrAg test, which FM stain confirmed that capsule-deficient Cryptococcus infections were observed in four cases. Eight isolated cases were identified as follows: six cases were infection with Cryptococcus neoformans and two cases were Cryptococcus gattii.

Real-time polymerase chain reaction detection of Cryptococcus neoformans and Cryptococcus gattii in human samples

We report a TaqMan real-time polymerase chain reaction (PCR) protocol for diagnosing cryptococcosis. Specificity was tested with 33 fungal strains. The 7 clinical samples found positive by culture also tested positive by real-time PCR. No false negatives were found among the 94 clinical samples that were negative by culture for Cryptococcus spp. The sensitivity threshold was about 10 plasmid copies per assay.

False-negative cerebrospinal fluid cryptococcal antigen test due to small-colony variants of Cryptococcus neoformans meningitis in a patient with cystopleural shunt

This is the first report of a small-colony variant Cryptococcus neoformans isolated from the cerebrospinal fluid of a patient with cystopleural shunt associated chronic meningitis. Cryptococcal antigen testing of the cerebrospinal fluid and the serum were both negative. The atypical morphology and the false-negative test may lead to delay of diagnosis and treatment.

Técnicas histopatológicas no diagnóstico de criptococose por Cryptococcus deficiente de cápsula: relato de caso

Caso de criptococose por Cryptococcus deficiente de cápsula, no qual cultivo do espécime clínico e pesquisa do antígeno capsular no líquor e soro foram negativos. As técnicas histopatológicas foram: Hematoxilina-eosina, Grocott, Mucicarmim de Mayer e Fontana-Masson. Confirmou-se o diagnóstico do Cryptococcus deficiente de cápsula pela técnica de Fontana-Masson e pela imunofluorescência direta. É discutida a potencialidade das técnicas histoquímicas.