Cryptococcosis: clinical and biological aspects

Intravascular clearance of disseminating Cryptococcus neoformans in the brain can be improved by enhancing neutrophil recruitment in mice

Extrapulmonary dissemination of Cryptococcus neoformans (C. neoformans) is one of the most critical steps in the development of meningoencephalitis. Here, we report that clearance of the disseminating C. neoformans occurs within the brain microvasculature. Interestingly, the efficiency of the intravascular clearance in the brain is reduced compared to that in the lung. Intravascular clearance is mainly mediated by neutrophils, and complement C5a receptor signaling is crucial for mediating neutrophil recruitment in the vasculature. C. neoformans stimulated actin polymerization of neutrophils is critically involved in their recruitment to the lung, which is associated with the unique vascular structure detected in the lung. The relatively lower efficiency of fungal clearance in the brain vasculature correlates with less efficient recruitment of neutrophils. Accordingly, intravascular clearance of C. neoformans in the brain could be remarkably improved by increasing the recruitment of neutrophils. We conclude that neutrophils have the ability to eliminate C. neoformans arrested in the vasculature. However, insufficient recruitment of neutrophils limited the optimal clearance of this microorganism in the brain. These results imply that a therapeutic strategy aimed at enhancing the accumulation of neutrophils could help prevent cryptococcal meningoencephalitis.

Cryptococcosis mimicking cutaneous cellulitis in a patient suffering from rheumatoid arthritis: a case report

Background

Cryptococcus neoformans is an encapsulated yeast and the most frequent cryptococcal species found in humans. Cryptococcosis is considered an opportunistic infection as it affects mainly immunosuppressed individuals. In humans, C. neoformans causes three types of infections: pulmonary cryptococcosis, cryptococcal meningitis and wound or cutaneous cryptococcosis.

Case Presentation

An 81-year-old woman developed severe necrotizing cellulitis on her left arm without any preceding injury. The patient had been treated with systemic corticosteroids over twenty years for rheumatoid arthritis (RA). Skin biopsies of the wound area were initially interpreted as cutaneous vasculitis of unknown etiology. However, periodic acid Schiff staining and smear analysis later revealed structures consistent with Cryptococcus neoformans, and the infection was subsequently confirmed by culture. After the initiation of therapy with fluconazole 400 mg per day the general condition and the skin ulcers improved rapidly and the patient was discharged to a rehabilitation facility. Subsequently surgical debridement and skin grafting were performed.

Conclusions

Opportunistic infections such as cryptococcosis can clinically and histologically mimic cutaneous vasculitis and have to be investigated rigorously as a differential diagnosis in immunosuppressed patients.

A prospective descriptive study of cryptococcal meningitis in HIV uninfected patients in Vietnam - high prevalence of Cryptococcus neoformans var grubii in the absence of underlying disease

Background

Most cases of cryptococcal meningitis occur in patients with HIV infection: the course and outcome of disease in the apparently immunocompetent is much more poorly understood. We describe a cohort of HIV uninfected Vietnamese patients with cryptococcal meningitis in whom underlying disease is uncommon, and relate presenting features of patients and the characteristics of the infecting species to outcome.

Methods

A prospective descriptive study of HIV negative patients with cryptococcal meningitis based at the Hospital for Tropical Diseases, Ho Chi Minh City. All patients had comprehensive clinical assessment at baseline, were cared for by a dedicated study team, and were followed up for 2 years. Clinical presentation was compared by infecting isolate and outcome.

Results

57 patients were studied. Cryptococcus neoformans var grubii molecular type VN1 caused 70% of infections; C. gattii accounted for the rest. Most patients did not have underlying disease (81%), and the rate of underlying disease did not differ by infecting species. 11 patients died while in-patients (19.3%). Independent predictors of death were age ≥ 60 years and a history of convulsions (odds ratios and 95% confidence intervals 8.7 (1 - 76), and 16.1 (1.6 - 161) respectively). Residual visual impairment was common, affecting 25 of 46 survivors (54.3%). Infecting species did not influence clinical phenotype or outcome. The minimum inhibitory concentrations of flucytosine and amphotericin B were significantly higher for C. neoformans var grubii compared with C. gattii (p < 0.001 and p = 0.01 respectively).

Conclusion

In HIV uninfected individuals in Vietnam, cryptococcal meningitis occurs predominantly in people with no clear predisposing factor and is most commonly due to C. neoformans var grubii. The rates of mortality and visual loss are high and independent of infecting species. There are detectable differences in susceptibility to commonly used antifungal drugs between species, but the clinical significance of this is not clear.

Diversity of and yeasts (Basidiomycota) inhabiting arbuscular mycorrhizal roots or spores

The genera Cryptococcus and Dioszegia contain basidiomycetous yeasts found in a wide range of habitats. Primers to amplify the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA (nrDNA) of arbuscular mycorrhizal fungi (AMF) also allow detecting members of this yeast group. Here we report the results of a sequence analysis using maximum parsimony on a set of 50 ITS sequences of yeasts associated with AMF structures (roots of 26 plant species, AM spores) from six field sites in Central Germany. Among 10 separated taxa, respectively five in the Tremellales and two in the Filobasidiales had unknown sequences. Therefore it was not possible to assign these sequences to any known species. The study indicates that exploring the diversity of Cryptococcus and Dioszegia in soil habitats with molecular methods might enlarge the actually estimated biodiversity of the group.

Effects of fluconazole singly and in combination with 5-fluorocytosine or amphotericin B in the treatment of cryptococcal meningoencephalitis in an intracranial murine model

In this study we developed a highly reproducible intracranial murine model of cryptococcosis. Mice (Balb/c, 5-7 weeks old) were challenged intracranially and treated with intermediate (30 mg/kg) or high (90 mg/kg) dose fluconazole, and amphotericin B (0.75 mg/kg), administered singly or in combination with flucytosine (100 mg/kg). Survival and brain CFU analyses were performed. Effect of fluconazole prophylaxis was also determined. Our data show that the developed model mimics clinical signs of cryptococcal meningitis. In single treatment, fluconazole (30 mg/kg) was more efficacious than amphotericin B or flucytosine (P < 0.0001). Combination treatment led to significantly increased anticryptococcal activity, which was highest for high dose fluconazole + flucytosine (P < 0.0001). However, no significant difference was observed between high dose fluconazole treatment with and without flucytosine (P >0.05). Fluconazole prophylaxis led to a significant decrease in brain CFU. In conclusion, high dose fluconazole administered post-infection, or as prophylaxis, may be highly efficacious in the treatment and prevention of meningoencephalitis.