Distribution and association between environmental and clinical isolates of Cryptococcus neoformans in Bogotá-Colombia, 2012-2015

Molecular characterization of clinical and environmental isolates from the Cryptococcus neoformans/C. Gattii species complexes of Maceió, Alagoas, Brazil

Cryptococcosis is one of the major life-threatening opportunistic/systemic fungal diseases of worldwide occurrence, which can be asymptomatic or establish pneumonia and meningoencephalitis mainly in immunosuppressed patients, caused by the Cryptococcus neoformans and C. gattii species complexes. Acquisition is by inhaling fungal propagules from avian droppings, tree hollows and decaying wood, and the association of the molecular types with geographic origin, virulence and antifungal resistance have epidemiological importance. Since data on cryptococcosis in Alagoas are limited, we sought to determine the molecular types of etiological agents collected from clinical and environmental sources. We evaluated 21 isolates previously collected from cerebrospinal fluid and from environment sources (pigeon droppings and tree hollows) in Maceió-Alagoas (Brazil). Restriction fragment length polymorphism of URA5 gene was performed to characterize among the eight standard molecular types (VNI-VNIV and VGI-VGIV). Among isolates, 66.67% (14) were assigned to C. neoformans VNI - 12 of them (12/14) recovered from liquor and 2 from a tree hollow (2/14). One isolate from pigeon droppings (4.76%) corresponded to C. neoformans VNIV, while five strains from tree hollows and one from pigeon droppings (6, 28.57%) to C. gattii VGII. VNI-type was present in clinical and environmental samples and most C. neoformans infections were observed in HIV-positive patients, while types VNIV and VGII were prevalent in environmental sources in Alagoas. This is the first molecular characterization of Cryptococcus spp. in Alagoas, our study provides additional information on the ecoepidemiology of Cryptococcus spp. in Brazil, contributing to a closer view of the endemic species.

The Predominance of a Specific Genotype of Cryptococcus neoformans var. Grubii in China and Japan

Background

The extensive deployment of molecular genotyping methods is the top reliable keyword to characterize the population genetic structure of C. neoformans in the past decade. However, studies involving genotypic analysis of C. neoformans var. grubii from China and Japan are limited.

Objectives

We address this challenge to determine the genotype distribution of C. neoformans var. grubii strains from China and Japan.

Methods

Genotypic analysis of 52 C. neoformans var. grubii isolates was performed using multilocus microsatellite typing (MLMT) based on the sequence analysis of 3 functional genes. In order to place the herein-studied strains into the global picture, 22 strains randomly selected from the 52 strains studied by MLMT were also analyzed by restriction fragment length polymorphism analysis of the orotidine monophosphate pyrophosphorylase gene (URA5-RFLP), M13 PCR-fingerprinting, and multilocus sequence typing (MLST).

Results

MLMT classified 46 (88.5%) of the 52 strains as genotype MLMT-17. The high prevalence of the MLMT-17 type was observed for environmental and clinical isolates from China and Japan. URA5-RFLP analysis, M13 PCR-fingerprinting, and MLST showed that most of these belong to the VNI/ST5 (M5) genotype.

Conclusions

Our study suggests the predominance of a specific genotype of C. neoformans var. grubii in China and Japan.

Amino acid permeases in Cryptococcus neoformans are required for high temperature growth and virulence; and are regulated by Ras signaling

Cryptococcosis is an Invasive Fungal Infection (IFI) caused by Cryptococcus neoformans, mainly in immunocompromised patients. Therapeutic failure due to pathogen drug resistance, treatment inconstancy and few antifungal options is a problem. The study of amino acid biosynthesis and uptake represents an opportunity to explore possible development of novel antifungals. C. neoformans has 10 amino acids permeases, two of them (Aap3 and Aap7) not expressed at the conditions tested, and five were studied previously (Aap2, Aap4, Aap5, Mup1 and Mup3). Our previous results showed that Aap4 and Aap5 are major permeases with overlapping functions. The aap4Δ/aap5Δ double mutant fails to grow in amino acids as sole nitrogen source and is avirulent in animal model. Here, we deleted the remaining amino acid permeases (AAP1, AAP6, AAP8) that showed gene expression modulation by nutritional condition and created a double mutant (aap1Δ/aap2Δ). We studied the virulence attributes of these mutants and explored the regulatory mechanism behind amino acid uptake in C. neoformans. The aap1Δ/aap2Δ strain had reduced growth at 37°C in L-amino acids, reduced capsule production and was hypovirulent in the Galleria mellonella animal model. Our data, along with previous studies, (i) complement the analysis for all 10 amino acid permeases mutants, (ii) corroborate the idea that these transporters behave as global permeases, (iii) are required during heat and nutritional stress, and (iv) are important for virulence. Our study also indicates a new possible link between Ras1 signaling and amino acids uptake.