Molecular epidemiology and antifungal susceptibility profiles of clinical Cryptococcus neoformans/Cryptococcus gattii species complex

A Comprehensive Review of Identification Methods for Pathogenic Yeasts: Challenges and Approaches

Given the increasing incidence of yeast infections and the presence of drug-resistant isolates, accurate identification of the pathogenic yeasts is essential for the management of yeast infections. In this review, we tried to introduce the routine and novel techniques applied for yeast identification. Laboratory identification methods of pathogenic yeast are classified into three categories; I. conventional methods, including microscopical and culture-base methods II. biochemical/physiological-processes methods III. molecular methods. While conventional and biochemical methods require more precautions and are not specific in some cases, molecular diagnostic methods are the optimum tools for diagnosing pathogenic yeasts in a short time with high accuracy and specificity, and having various methods that cover different purposes, and affordable costs for researchers. Nucleotide sequencing is a reference or gold standard for identifying pathogenic yeasts. Since it is an expensive method, it is not widely used in developing countries. However, novel identification techniques are constantly updated, and we recommend further studies in this field. The results of this study will guide researchers in finding more accurate diagnostic method(s) for their studies in a short period of time.

The clinic-based predictive modeling for prognosis of patients with cryptococcal meningitis

BACKGROUND

Cryptococcal meningitis (CM) is the most common fungal infection of the central nervous system that can cause significant morbidity and mortality. Although several prognostic factors have been identified, their clinical efficacy and use in combination to predict outcomes in immunocompetent patients with CM are not clear. Therefore, we aimed to determine the utility of those prognostic factors alone or in combination in predicting outcomes of immunocompetent patients with CM.

METHODS

The demographic and clinical data of patients with CM were collected and analyzed. The clinical outcome was graded by the Glasgow outcome scale (GOS) at discharge, and patients were divided into good (score of 5) and unfavorable (score of 1-4) outcome groups. Prognostic model was created and receiver-operating characteristic curve analyses were conducted.

RESULTS

A total of 156 patients were included in our study. Patients with higher age at onset (p = 0.021), ventriculoperitoneal shunt placement (p = 0.010), Glasgow Coma Scale (GCS) score of less than 15(p< 0.001), lower CSF glucose concentration (p = 0.037) and immunocompromised condition (p = 0.002) tended to have worse outcomes. Logistic regression analysis was used to create a combined score which had a higher AUC (0.815) than those factors used alone for predicting outcome.

CONCLUSIONS

Our study shows that a prediction model based on clinical characteristics had satisfactory accuracy in prognostic prediction. Early recognition of CM patients at risk of poor prognosis using this model would be helpful in providing timely management and therapy to improve outcomes and to identify individuals who warrant early follow-up and intervention.

Trend of pediatric cryptococcosis in a tertiary care centre and review of literature

PURPOSE

Cryptococcosis is one of the most significant systemic fungal infections worldwide. Epidemiological data for pediatric cryptococcosis is very limited. Therefore, we planned this study to determine the burden of cryptococcosis in the pediatric population at our tertiary care center and performed review of literature.

MATERIAL AND METHODS

In this retrospective study, all the patients less than 18 years of age were diagnosed with cryptococcosis, from January 2015-June 2021 were included. Demographic, clinical, and laboratory details of all the patients were noted. Furthermore, PubMed and MedLine databases were comprehensively searched for cases of pediatric cryptococcosis till June 2021.

RESULTS

Of the total 5420 samples from suspected cryptococcosis cases processed at mycology laboratory, a total of 21 episodes of cryptococcosis (0.39%) were identified in 15 pediatric patients. The majority of the patients were apparently immunocompetent (10/15). Central nervous system (CNS) cryptococcosis was the most common presentation, followed by disseminated disease. All the isolates were identified as Cryptococcus neoformans (formerly referred to as C. neoformans var grubii), except one that was identified as Papiliotrema laurentii (formerly referred to as Cryptococcus laurentii). A standard treatment regimen inclusive of induction and maintenance therapy was provided in only five patients. The literature review revealed a total of 125 studies describing 1134 cases, of which 76.4% are reported from outside Asia, the majority (65.7%) restricted to CNS with C. neoformans as the commonest species. The management profile divulged a significantly higher use of standard drug regimen in Asia as compared to the rest of the world. Mortality of 13.32% was noted worldwide.

CONCLUSION

To the best of our knowledge, this is the first clinico-epidemiological study of pediatric cryptococcosis from India and the largest retrospective study worldwide. The rising incidence among immunocompetent individuals, especially in Asia, is a matter of concern. Clinical suspicion and early diagnosis are the cornerstones for the management of cases.

Anthraquinones from Aloe spp. inhibit Cryptococcus neoformans sensu stricto: effects against growing and mature biofilms

This study aimed to evaluate the in vitro effect of aloe emodin, barbaloin and chrysophanol on growing and mature biofilms of Cryptococcus neoformans sensu stricto. The compounds were added at the moment of inducing biofilm growth or after growth for 72 h to evaluate their effects on growing and mature biofilms, respectively. Then, biofilm biomass was evaluated by crystal violet staining and metabolic activity by the XTT reduction assay. Morphological alterations were also evaluated by laser scanning confocal microscopy. Aloe emodin and barbaloin affected growing biofilms and disrupted mature biofilms, reducing metabolic activity by > 60% and biomass by > 70%. Chrysophanol only inhibited mature biofilms, but to a lesser extent. In conclusion, anthraquinones, especially aloe emodin and barbaloin, show a relevant effect against growing and mature biofilms of C. neoformans sensu stricto.

HOG1 has an essential role in the stress response, virulence and pathogenicity of Cryptococcus gattii

Cryptococcus gattii (C. gattii) is a lethal pathogen that causes the majority of cryptococcosis cases in previously healthy individuals. This pathogen poses an increasing threat to global public health, but the mechanisms underlying the pathogenesis have remained to be fully elucidated. In the present study, the role of high-osmolarity glycerol (HOG)1 in the stress reaction and virulence control of C. gattii was characterized by deleting the HOG1 gene using the clinical isolate strain CZ2012, and finally, the virulence and pathogenic traits of the deletion strain were defined. Deletion of the HOG1 gene resulted in notable growth defects under stress conditions (high salt and antifungal drugs), but different traits were observed under oxidative stress conditions (hydrogen peroxide). Similarly, the C. gattii hog1Δ strains (deletion of HOG1) also displayed decreased capsule production and melanin synthesis. Furthermore, mice infected with the hog1Δ strain had longer survival times than those infected with the wild-type strain and the reconstituted strain. The hog1Δ strain recovered from infected organs exhibited significant growth defects in terms of decreased colony count and size. The present results suggested that HOG1 has a significant role in the virulence of C. gattii and these results may help to elucidate the pathogenesis of C. gattii.

Clinical features and para-clinical findings of cryptococcal meningitis in the North of Iran during 2011-19

Background and Purpose:

Cryptococcal meningitis (CM) is a serious fungal infection that especially affects patients with human immunodeficiency virus (HIV). In this regard, the present retrospective study aimed to analyze the clinical and laboratory features and therapeutic outcomes of patients with CM admitted to two teaching referral centers in the north of Iran during 2011-19.

Materials and Methods:

This study was performed on all the hospitalized patients diagnosed with CM in two therapeutic centers of infectious diseases in the north of Iran. The required data, such as demographic characteristics and clinical and paraclinical features of patients, were extracted and entered in the information forms. Finally, the collected data were analyzed in SPSS software (version 16).

Results:

For the purpose of the study, records of 12 confirmed CM patients were evaluated in this research. Based on the results, 75% of the patients were male. Moreover, the average age of the subjects was 40.33± 8.93 years old and 66.6% of them (n=8) were HIV-positive. Other underlying diseases among HIV-positive patients included infection with hepatitis C virus (25%) and a history of tuberculosis (25%). In total, three HIV-negative patients suffered from Hodgkin lymphoma (25%), sarcoidosis (25%), and asthma (25%) and one patient (25%) had no underlying disease. Headache (75%), weakness, and fatigue (75%) were the most common symptoms among the participants. The cluster of differentiation 4 (CD4) count in all HIV-positive patients was less than 100 cells/μl. There was no significant difference between symptoms in HIV-positive and HIV-negative patients. Besides, no significant difference was observed between the groups of HIV-positive and HIV-negative patients regarding the period between the onset of symptoms and diagnosis of CM, the length of hospital stay, and the duration of antifungal medication consumption. In total, three patients (25%) expired, and six patients recovered. The CM recurred in two HIV-negative and one HIV-positive subjects; the two HIV-negative patients were treated, while the HIV-positive patient expired due to this recurrence.

Conclusion:

Clinical features and cerebrospinal fluid parameters were not different in HIV-positive and HIV-negative participants. Despite the fact that CM is not common in Iran, due to the increasing number of immunosuppressive patients, the differential diagnosis of CM should be considered for patients with signs and symptoms of infection in the central nervous system.

Molecular typing, in vitro susceptibility and virulence of Cryptococcus neoformans/Cryptococcus gattii species complex clinical isolates from south-eastern Brazil

BACKGROUND

Cryptococcus neoformans/ Cryptococcus gattii species complex is composed of encapsulated yeast species that are causative agents of cryptococcosis. The characterisation of pathogenic Cryptococcus species provides useful data for epidemiological studies as well as the clinical diagnosis and treatment of patients.

OBJECTIVES

This study aimed to characterise the epidemiology, antifungal susceptibility and virulence of 72 clinical strains isolated from cryptococcosis cases between 2012 and 2017 in a tertiary reference hospital in south-eastern Brazil.

METHODS

Species and molecular types were molecularly assessed by PCR and PCR-restriction fragment length polymorphism (RFLP) of the URA5 gene. Antifungal susceptibility testing was performed according to the CLSI protocols. The virulence was studied in a Galleria mellonella infection model.

RESULTS

The most frequently isolated strain was C. neoformans molecular type VNI (61/72; 84.7%), although C. neoformans molecular type VNII (3/72; 4.2%) was also isolated. Additionally, C. deuterogattii molecular type VGII (8/72; 11.1%) was present, but most frequently from non-HIV-infected patients. Non-wild-type phenotype to the antifungals was observed in 26.4% (19/72) of the C. neoformans and C. deuterogattii clinical isolates, and the latter demonstrated higher MIC to fluconazole and itraconazole than C. neoformans clinical isolates. Finally, the virulence of C. neoformans and C. deuterogattii clinical isolates was diverse in G mellonella larvae and uncorrelated with the virulence factors of melanin and capsule.

CONCLUSIONS

The assessment of the spread of cryptococcal species and molecular types as well as the pattern of corresponding antifungal susceptibility and virulence aids in surveil the emergence of resistant strains, ensuring more accurate management of the cryptococcal infection.

Antifungal effect of anthraquinones against Cryptococcus neoformans: detection of synergism with amphotericin B

The emergence of tolerant Cryptococcus neoformans strains to antifungals has been described. It has directed researchers to screen for new antimicrobial compounds. In this context, several plant-derived compounds, such as anthraquinones (aloe emodin, barbaloin, and chrysophanol), have been investigated for their antimicrobial properties. This study aimed to evaluate the in vitro effect of aloe emodin, barbaloin and chrysophanol on C. neoformans in vitro growth. In addition, the interaction between these anthraquinones and amphotericin B and itraconazole was evaluated. Initially, the minimum inhibitory concentrations (MIC) of these compounds were determined against 17 strains of C. neoformans by the broth microdilution method and then pharmacological interaction assays were performed with 15 strains by the checkerboard method. Aloe emodin, barbaloin, and chrysophanol showed minimum inhibitory concentrations of 236.82-473.65 μM (64-128 μg/mL), 153-306 μM (64-128 μg/ml) and ≥1007 μM (≥256 μg/ml), respectively. Furthermore, aloe emodin (11/15), barbaloin (13/15), and chrysophanol (12/15) showed pharmacological synergism (FICI < 0.5) with amphotericin B at subinhibitory concentrations (MIC/4). The itraconazole-aloe emodin interaction was additive (1/15) (0.5 < FICI < 1.0). The itraconazole-barbaloin interaction were synergistic (2/15) and additive (5/15); whereas itraconazole-chrysophanol interactions were additive (2/15). Anthraquinones, especially aloe emodin and barbaloin, present in vitro antifungal activity against C. neoformans and potentiate the antifungal activity of amphotericin B.

Multi-locus Sequence Typing and Whole Genome Sequence Analysis of Cryptococcus neoformans Isolated from Clinical Specimens in Vajira Hospital, Bangkok, Thailand

The basidiomycete yeast Cryptococcus neoformans causes disease in immunocompromized patients. Whole genome sequencing (WGS) technology provides insights into the molecular epidemiology of C. neoformans. However, the number of such studies is limited. Here we used WGS and multilocus sequence typing (MLST) to determine the genetic diversity of C. neoformans isolates and genetic structures of their populations among patients admitted to a single hospital in Bangkok, Thailand. Seven isolates from six patients collected during 1 year were identified as C. neoformans sensu stricto according to colony morphology, microscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nucleotide sequence analysis of internal transcribed sequences. These isolates were sensitive to the antifungal drugs amphotericin B, fluconazole, 5-flucytosine, voriconazole, itraconazole and posaconazole and were mating type α and molecular type VNI. MLST analysis identified ST4, ST5 and ST6. We further employed WGS to determine the genetic diversity and relationships of C. neoformans isolated here combined with C. neoformans sequences data acquired from a public database (n = 42). We used the data to construct a phylogenetic tree. WGS provided additional genomics data and achieved high discriminatory power for identifying C. neoformans isolates isolated in Thailand. This report further demonstrates the applicability of WGS analysis for conducting molecular epidemiology and provides insight into the genetic diversity of C. neoformans isolates from one hospital in Thailand.

Multicenter Cryptococcal Antigen Screening of HIV-Infected Patients in Iran

Early diagnosis and targeted preemptive antifungal treatment are crucial in reducing cryptococcal meningitis (CM)-related mortality in individuals living with human immunodeficiency virus (HIV). The present study was performed to determine cryptococcal antigenemia and outcomes among HIV-infected patients in Iran. This multicenter prospective study was conducted between October 2016 and December 2018. For the purpose of the study, blood samples were randomly collected from 177 profoundly immunosuppressed (CD4+ counts < 200 cells/µL) HIV-positive individuals in six major cities of Iran. The patients were antiretroviral therapy-naive or had received inadequate medication. The stored sera were screened for cryptococcal antigen (CrAg), using point-of-care lateral flow assay (IMMY® diagnostics, Norman, OK, US). Overall, out of the 174 asymptomatic patients, 3 (1.72%) cases were CrAg-positive using the LFA in serum. Accordingly, the prevalence of cryptococcal antigenemia was 7.14%, 0%, and 1.2% in the patients with the CD4+ counts of < 50, 50-100, and 100-200 cells/μL, respectively. The median age of the patients with antigenemia was 36 years (age range 8-55 years). The median CD4+ count of the cohort was 98 cells/μL (range 14-200 cells/μL). Routine screening of Iranian HIV-infected patients with CD4+ count of < 50 cells/µL before initiating antiretroviral therapy is justified. It is suggested to conduct more inclusive research throughout the whole country on more patients to recommend screening cryptococcal antigen strongly.

Impaired consciousness and decreased glucose concentration of CSF as prognostic factors in immunocompetent patients with cryptococcal meningitis

Background

Cryptococcal meningitis (CM) is the most common fungal infection of the central nervous system and has high morbidity and mortality. Almost studies about prognostic factors have largely focused on the immunocompromised population rather than immunocompetent patients. So that we sought to conduct a retrospective study to determine prognostic factors which predict the outcomes in immunocompetent patients with CM.

Methods

We retrospectively collected and analyzed the demographic and clinical data of 76 apparently immunocompetent patients with cryptococcal meningitis from January 2003 to June 2019 in China. The clinical outcome was graded by the Glasgow outcome scale (GOS) at discharge, and patients were divided into good (score of 5) and unfavorable (score of 1–4) outcome groups, potential prognostic factors were analyzed.

Results

Non-parametric test confirmed that unfavorable outcome was associated with lower glucose level of CSF(P = 0.001), and Pearson’s χ2 analysis confirmed that unfavorable outcome was associated with opening pressure of CSF(>300mmH20, P = 0.038), impaired consciousness (P = 0.001), hydrocephalus(P = 0.045), and Shunt surgery (P = 0.045), and then multiple logistic regression analysis confirmed that impaired consciousness(P = 0.015) and lower glucose concentration of CSF(P = 0.012) increased the likelihood of unfavorable outcome in CM patients.

Conclusion

Impaired consciousness and decreased glucose concentration of CSF were independently prognostic factors which predict the unsatisfactory outcome in immunocompetent patients with CM.