Yeast Cryptococcus Neoformans Research Articles

Discovery of a Modified Tetrapolar Sexual Cycle in Cryptococcus amylolentus and the Evolution of MAT in the Cryptococcus Species Complex

Sexual reproduction in fungi is governed by a specialized genomic region called the mating-type locus (MAT). The human fungal pathogenic and basidiomycetous yeast Cryptococcus neoformans has evolved a bipolar mating system (a, α) in which the MAT locus is unusually large (>100 kb) and encodes >20 genes including homeodomain (HD) and pheromone/receptor (P/R) genes. To understand how this unique bipolar mating system evolved, we investigated MAT in the closely related species Tsuchiyaea wingfieldii and Cryptococcus amylolentus and discovered two physically unlinked loci encoding the HD and P/R genes. Interestingly, the HD (B) locus sex-specific region is restricted (∼2 kb) and encodes two linked and divergently oriented homeodomain genes in contrast to the solo HD genes (SXI1α, SXI2 a) of C. neoformans and Cryptococcus gattii. The P/R (A) locus contains the pheromone and pheromone receptor genes but has expanded considerably compared to other outgroup species (Cryptococcus heveanensis) and is linked to many of the genes also found in the MAT locus of the pathogenic Cryptococcus species. Our discovery of a heterothallic sexual cycle for C. amylolentus allowed us to establish the biological roles of the sex-determining regions. Matings between two strains of opposite mating-types (A1B1×A2B2) produced dikaryotic hyphae with fused clamp connections, basidia, and basidiospores. Genotyping progeny using markers linked and unlinked to MAT revealed that meiosis and uniparental mitochondrial inheritance occur during the sexual cycle of C. amylolentus. The sexual cycle is tetrapolar and produces fertile progeny of four mating-types (A1B1, A1B2, A2B1, and A2B2), but a high proportion of progeny are infertile, and fertility is biased towards one parental mating-type (A1B1). Our studies reveal insights into the plasticity and transitions in both mechanisms of sex determination (bipolar versus tetrapolar) and sexual reproduction (outcrossing versus inbreeding) with implications for similar evolutionary transitions and processes in fungi, plants, and animals.

Cryptococcus neoformans: The Model Organism for Yeast Antifungal Drug Susceptibility Testing

We describe an approach to antifungal susceptibility testing of the yeast Cryptococcus neoformans that shows promise for predicting the mycological response in patients to treatment. Quantitative cultures of the cerebrospinal fluid provide a direct measure of the patient's mycological response to treatment and have been used in multiple studies to identify the most promising antifungal drugs for subsequent testing in larger clinical studies. Using these quantitative measures of response, a modified macrobroth dilution assay system shows the potential for predicting the response of an individual patient to treatment with amphotericin B, fluconazole, or the combination of amphotericin B plus flucytosine. We describe this modified macrobroth dilution assay method, the statistical approach for assessing susceptibility, and the clinical decisions that can be guided by this in vitro antifungal drug susceptibility testing.

Transcriptomic and proteomic analyses of the Aspergillus fumigatus hypoxia response using an oxygen-controlled fermenter

BackgroundAspergillus fumigatus is a mold responsible for the majority of cases of aspergillosis in humans. To survive in the human body, A. fumigatus must adapt to microenvironments that are often characterized by low nutrient and oxygen availability. Recent research suggests that the ability of A. fumigatus and other pathogenic fungi to adapt to hypoxia contributes to their virulence. However, molecular mechanisms of A. fumigatus hypoxia adaptation are poorly understood. Thus, to better understand how A. fumigatus adapts to hypoxic microenvironments found in vivo during human fungal pathogenesis, the dynamic changes of the fungal transcriptome and proteome in hypoxia were investigated over a period of 24 hours utilizing an oxygen-controlled fermenter system.ResultsSignificant increases in transcripts associated with iron and sterol metabolism, the cell wall, the GABA shunt, and transcriptional regulators were observed in response to hypoxia. A concomitant reduction in transcripts was observed with ribosome and terpenoid backbone biosynthesis, TCA cycle, amino acid metabolism and RNA degradation. Analysis of changes in transcription factor mRNA abundance shows that hypoxia induces significant positive and negative changes that may be important for regulating the hypoxia response in this pathogenic mold. Growth in hypoxia resulted in changes in the protein levels of several glycolytic enzymes, but these changes were not always reflected by the corresponding transcriptional profiling data. However, a good correlation overall (R2 = 0.2, p < 0.05) existed between the transcriptomic and proteomics datasets for all time points. The lack of correlation between some transcript levels and their subsequent protein levels suggests another regulatory layer of the hypoxia response in A. fumigatus.ConclusionsTaken together, our data suggest a robust cellular response that is likely regulated both at the transcriptional and post-transcriptional level in response to hypoxia by the human pathogenic mold A. fumigatus. As with other pathogenic fungi, the induction of glycolysis and transcriptional down-regulation of the TCA cycle and oxidative phosphorylation appear to major components of the hypoxia response in this pathogenic mold. In addition, a significant induction of the transcripts involved in ergosterol biosynthesis is consistent with previous observations in the pathogenic yeasts Candida albicans and Cryptococcus neoformans indicating conservation of this response to hypoxia in pathogenic fungi. Because ergosterol biosynthesis enzymes also require iron as a co-factor, the increase in iron uptake transcripts is consistent with an increased need for iron under hypoxia. However, unlike C. albicans and C. neoformans, the GABA shunt appears to play an important role in reducing NADH levels in response to hypoxia in A. fumigatus and it will be intriguing to determine whether this is critical for fungal virulence. Overall, regulatory mechanisms of the A. fumigatus hypoxia response appear to involve both transcriptional and post-transcriptional control of transcript and protein levels and thus provide candidate genes for future analysis of their role in hypoxia adaptation and fungal virulence.

In vitro antifungal activities of longan (Dimocarpus longan Lour.) seed extract

Longan, Dimocarpus longan Lour., contains polyphenolic compounds which exhibit several pharmacological properties. This study aims to evaluate antifungal activities of longan fruit extract in comparison to its active compounds. The results showed that longan seed exhibited antifungal activity against the opportunistic yeasts (Candida species and Cryptococcus neoformans). In contrast, longan pulp and whole fruit did not demonstrate any inhibitory effects. Ellagic acid showed the most potent antifungal activity followed by corilagin and gallic acid, respectively. Ellagic acid inhibited Candida parapsilosis and C. neoformans more effectively than Candida krusei and also some Candida albicans clinical strains. Baidam cultivar possessed higher antifungal activity (MIC=500–4000μg/ml) as it contained higher contents of ellagic acid and gallic acid than Edor (MIC=1000–8000μg/ml). For antibacterial activity, only corilagin and gallic acid possessed weak to moderate inhibitory effects against Staphylococcus aureus and Streptococcus mutans, respectively. Longan seed was then applied in the oral care products. Longan effervescent granule (5% extract) significantly reduced adhesion of C. albicans to acrylic strips. Mouthwash containing 0.5% extract exhibited good antifungal activity compared to a commercial product. These findings indicated that longan seed extract and its polyphenolic compounds can be used as an antifungal agent in oral care products for the treatment of opportunistic yeast infection.

Sodium butyrate inhibits pathogenic yeast growth and enhances the functions of macrophages

Butyrate is a short-chain fatty acid that is produced by several human commensal bacteria, such as Clostridium and Lactobacillus species. Butyrate is also known to inhibit histone deacetylase. In this study we assessed the antifungal activity of sodium butyrate (SB) against the human pathogenic yeasts Candida albicans, Candida parapsilosis and Cryptococcus neoformans. The growth and virulence traits of the yeasts were assayed in vitro and during interaction with macrophages in the presence of SB. SB strongly inhibited yeast growth in a concentration-dependent manner, inhibited virulence traits such as filamentation in C. albicans and melanization and capsule formation in C. neoformans and, importantly, significantly decreased yeast biofilm formation. SB also enhanced the antifungal activity of azole drugs. Notably, SB augmented the antifungal activity of macrophages by enhancing the production of reactive oxygen species. The phagocytic rate and killing activity of macrophages significantly increased in the presence of SB, which coincided with an increase in nitric oxide production. These results demonstrate that SB exerts significant antifungal activity on pathogenic yeasts and enhances the antimicrobial actions of macrophages in response to these microbes.

Identification of a Zds-like gene ZDS3 as a new mediator of stress resistance, capsule formation and virulence of the human pathogenic yeast Cryptococcus neoformans

The fungal Zds proteins are regulators of the serine/threonine phosphatase 2A (PP2A) and the protein kinase A. Here, we characterize a Zds-like gene ZDS3 that plays a broad range of roles in the basidiomycetous pathogenic yeast Cryptococcus neoformans. ZDS3 harbors the conserved activation domain ZDS_C of Zds proteins. By gene disruption, ZDS3 is shown to play roles in capsule production, cell wall integrity, growth at a high temperature, resistance to H(2)O(2) stress, osmotic pressures and glucose-dependent invasive growth on the agar. As a consequence, the disruption of ZDS3 resulted in complete loss of virulence in a mouse cryptococcosis model. The data suggest that ZDS3 is a novel mediator of the virulence of C. neoformans. Zds3 may serve as an antifungal drug target as no homologs are found in mammals.

Antimicrobial activity of mangrove plant ( Lumnitzera littorea)

Objective To investigate the antimicrobial activities of n-hexane, ethyl acetate and methanol extracts of the leaves of Lumnitzera littorea ( L. littorea) against six human pathogenic microbes. Methods The antimicrobial activity was evaluated using disc diffusion and microdilution methods. Results The antimicrobial activities of the crude extracts were increased with increasing the concentration. It is clear that n-hexane extract was the most effective extract. Additionally, Gram positive Bacillus cereus (B. cereus) appear to be the most sensitive strain while Pseudomonas aeruginosa (P. aeruginosa) and the yeast strains ( Candida albicans (C. albicans) and Cryptococcus neoformans (C. neoformans)) appear to be resistance to the tested concentrations since no inhibition zone was observed. The inhibition of microbial growth at concentration as low as 0.04 mg/mL indicated the potent antimicrobial activity of L. littorea extracts. Conclusions The obtained results are considered sufficient for further study to isolate the compounds responsible for the activity and suggesting the possibility of finding potent antibacterial agents from L. littorea extracts.

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit growth of yeast pathogens

Studies on yeasts exposed non-steroidal anti-inflammatory drugs (NSAIDs) such as acetylsalicylic acid (aspirin) as potential anti-mitochondrial antifungals. In this study, various NSAIDs were tested for antifungal activity on the human yeast pathogens Candida albicans and Cryptococcus neoformans. Our results suggest a dual action for these drugs, that is, antifungal as well as anti-inflammatory. These results could be useful in the treatment of fungal infections. Key words: Acetylsalicylic acid, antifungal, anti-inflammatory drugs, anti-mitochondrial,Candida albicans, Cryptococcus neoformans, Eremothecium ashbyi.

Efficient implementation of RNA interference in the pathogenic yeast Cryptococcus neoformans

An improved method has been developed for RNA interference in Cryptococcus neoformans, using opposing promoters to facilitate cloning and RNA interference targeting URA5 to allow selection of cells in which silencing is most effective. These advances significantly reduce the variability of silencing and the effort required for interference plasmid construction.

Cryptococcus neoformansas a Model for Radioimmunotherapy of Infections

There is an obvious and urgent need for novel approaches to treat infectious diseases. The use of monoclonal antibodies in therapy of infectious diseases is now experiencing renewed interest. During the last 5 years radioimmunotherapy (RIT), a modality previously developed only for cancer treatment, has been successfully adapted for the treatment of experimental fungal, bacterial, and viral infections. As our model organism for studying the efficacy, mechanisms, potential toxicity, and radioresistance to RIT, as well as for comparison of RIT with the existing antimicrobial therapies we have chosen the encapsulated yeast Cryptococcus neoformans (CN). The success of RIT approach in laboratory studies provides encouragement for feasibility of therapeutically targeting microbes with labeled antibodies. In addition, the creation of “panantibodies” for RIT which would recognize antigens shared by the whole class of pathogens such as fungi, for example, would facilitate the introduction of RIT into the clinic.

Antifungal and Antibacterial Activities of Four Malaysian Sponge Species (Petrosiidae)

Summary Aqueous and organic extracts from four marine sponges collected from the coastline of Malaysia were screened against six microorganisms, including the bacteria Staphylococcus aureus ATCC25923, Bacillus cereus ATCC11778, Pseudomonas aeruginosa ATCC27853, Escherichia coli ATCC35218, the yeasts Candida albicans ATCC10231 and Cryptococcus neoformans ATCC90112. All the sponge species in this study showed antibacterial activity against at least one bacterial strain and only one sponge species was significantly active against C. albicans. P. aeruginosa was considered resistant to all tested samples, since no inhibition zone was observed while the Gram-positive B. cereus was shown to be the most sensitive microorganism followed by C. albicans and S. aureus. The highest activity was obtained for the aqueous extract of Neopetrosia exigua against the Gram-positive bacteria B. cereus (inhibition zone 25 mm and MIC 0.07 mg/mL) and S. aureus (17.5 mm and 0.12 mg/mL) and against C. albicans (21 mm and 0.32 mg/mL). This extract is currently undergoing further analysis to identify the active compounds.

Disseminierte Papeln bei einer Patientin mit akuter myeloischer Leukämie

Cryptococcosis most commonly occurs in immunosuppressed patients. The pathogen is the yeast Cryptococcus neoformans. This article reports on the case of a 20-year-old female patient with acute myeloid leukemia who suddenly developed disseminated livid red papules and papulovesicles. The clinical picture and in particular the histopathology findings led to the diagnosis of cutaneous cryptococcosis, which was successfully treated with amphotericin B. For the differential diagnosis generalized herpes zoster, erythema exudativum multiforme and disseminated molluscum contagiosum must be considered. To confirm the diagnosis attempts can also be made to culture the pathogen from skin biopsy preparations. Furthermore, fungal spores can be rapidly and simply detected with the Tzanck test.

The ethnobotany, leaf anatomy, essential oil variation and biological activity of Pteronia incana (Asteraceae)

The only available ethnobotanical information on Pteronia incana has been recorded by the Montagu Museum in the Western Cape Province of South Africa. It was reported that the plant is used to treat influenza, fever, kidney ailments and backache. In common with other species of Pteronia, the plant contains an essential oil reminiscent of pine turpentine oil with β-pinene, limonene, 1,8-cineole, myrcene, spathulenol, p-cymene and methyleugenol as main compounds present in all or most of the samples, with smaller amounts of α-pinene, sabinene, γ-terpinene, terpinen-4-ol, biclogermacrene, globulol and α-bisabolol in some of the distillates. We investigated the oil composition of 11 individual plants collected at three geographically distant localities but found limited variation, both within and between populations. Leaf sections of P. incana showed that it is anatomically similar to P. divaricata in the presence of a secretory duct associated with the main vascular bundle (and often other bundles as well), in addition to glandular and non-glandular trichomes on both leaf surfaces. One yeast ( Cryptococcus neoformans), two Gram-negative bacteria ( Moraxella catarrhalis and Klebsiella pneumoniae) and one Gram-positive bacterium ( Mycobacterium smegmatis) were selected for antimicrobial activity studies using the minimum inhibitory concentration (MIC) microtitre plate method. The results showed that methanol:dichloromethane (MeOH:CH 2Cl 2) extracts were active against M. smegmatis (lowest MIC values of 0.5–0.8 mg/ml) and C. neoformans (lowest MIC values of 0.5–2.0 mg/ml). The essential oil was most active against C. neoformans (lowest MIC value of 0.3 mg/ml). These results provide a scientific rationale for the use of P. incana in Cape herbal medicine.

Chemical Synthesis and Biological Screening of 2‐Aminoimidazole‐Based Bacterial and Fungal Antibiofilm Agents

A collection of 2-aminoimidazole/triazole amides has been synthesized and screened for antibiofilm activity. This class of small molecules was found to modulate the biofilm activity of Pseudomonas aeruginosa, a multidrug-resistant strain of Acinetobacter baumannii (MDRAB), a methicillin-resistant Staphylococcus aureus strain (MRSA), Escherichia coli, Rhodospirillum salexigens, Staphylococcus epidermidis, Vibrio vulnificus, and vancomycin-resistant Enterococcus faecium as well as the yeast Candida albicans and Cryptococcus neoformans. Furthermore, lead compounds were found to not lyse red blood cells at active concentrations.

Septins enforce morphogenetic events during sexual reproduction and contribute to virulence of Cryptococcus neoformans

Septins are conserved, cytoskeletal GTPases that contribute to cytokinesis, exocytosis, cell surface organization and vesicle fusion by mechanisms that are poorly understood. Roles of septins in morphogenesis and virulence of a human pathogen and basidiomycetous yeast Cryptococcus neoformans were investigated. In contrast to a well-established paradigm in S. cerevisiae, Cdc3 and Cdc12 septin homologues are dispensable for growth in C. neoformans yeast cells at 24 degrees C but are essential at 37 degrees C. In a bilateral cross between septin mutants, cells fuse but the resulting hyphae exhibit morphological abnormalities, including lack of properly fused specialized clamp cells and failure to produce spores. Interestingly, post-mating hyphae of the septin mutants have a defect in nuclear distribution. Thus, septins are essential for the development of spores, clamp cell fusion and also play a specific role in nuclear dynamics in hyphae. In the post-mating hyphae the septins localize to discrete sites in clamp connections, to the septa and the bases of the initial emerging spores. Strains lacking CDC3 or CDC12 exhibit significantly reduced virulence in a Galleria mellonella model of infection. Thus, C. neoformans septins are vital to morphology of the hyphae and contribute to virulence.

Structure and Mode of Action of Microplusin, a Copper II-chelating Antimicrobial Peptide from the Cattle Tick Rhipicephalus (Boophilus) microplus

Microplusin, a Rhipicephalus (Boophilus) microplus antimicrobial peptide (AMP) is the first fully characterized member of a new family of cysteine-rich AMPs with histidine-rich regions at the N and C termini. In the tick, microplusin belongs to the arsenal of innate defense molecules active against bacteria and fungi. Here we describe the NMR solution structure of microplusin and demonstrate that the protein binds copper II and iron II. Structured as a single alpha-helical globular domain, microplusin consists of five alpha-helices: alpha1 (residues Gly-9 to Arg-21), alpha2 (residues Glu-27 to Asn-40), alpha3 (residues Arg-44 to Thr-54), alpha4 (residues Leu-57 to Tyr-64), and alpha5 (residues Asn-67 to Cys-80). The N and C termini are disordered. This structure is unlike any other AMP structures described to date. We also used NMR spectroscopy to map the copper binding region on microplusin. Finally, using the Gram-positive bacteria Micrococcus luteus as a model, we studied of mode of action of microplusin. Microplusin has a bacteriostatic effect and does not permeabilize the bacterial membrane. Because microplusin binds metals, we tested whether this was related to its antimicrobial activity. We found that the bacteriostatic effect of microplusin was fully reversed by supplementation of culture media with copper II but not iron II. We also demonstrated that microplusin affects M. luteus respiration, a copper-dependent process. Thus, we conclude that the antibacterial effect of microplusin is due to its ability to bind and sequester copper II.

The spindle pole body of the pathogenic yeast Cryptococcus neoformans: variation in morphology and positional relationship with the nucleolus and the bud in interphase cells

The spindle pole body (SPB) in the interphase cell of the pathogenic yeast Cryptococcus neoformans was studied in detail by freeze-substitution and serial ultrathin sectioning electron microscopy. The SPB was located on the outer nuclear envelope and appeared either dumbbell- or bar shaped. The dumbbell-shaped SPBs were 228-365 nm long with amorphous spheres on each end, each sphere being 78-157 nm in diameter. The bar-shaped SPBs were 103-260 nm long and 32-113 nm thick. They consisted of filamentous materials. The dumbbell-shaped SPBs were more frequent (61%) than the bar-shaped SPBs. The bar-shaped SPBs may be regarded as dumbbell-shaped SPBs whose spherical parts became sufficiently small. There seemed to be no relationship between the SPB shape and the cell cycle stage of G1-G2, since both types of SPB appeared not only in unbudded cells but also in budded cells and their appearance seems to be random. It is not clear at present whether morphological changes between dumbbell- and bar shapes have any physiological function. The SPB tended to be localized away from the nucleolus (141 degrees +/- 44 degrees), but localized randomly to the bud (97 degrees +/- 50 degrees). The present study highlights the necessity of observing a large number of micrographs in three dimensions to describe accurately the ultrastructure of the SPB in yeast.

A Microbial Polysaccharide Reduces the Severity of Rheumatoid Arthritis by Influencing Th17 Differentiation and Proinflammatory Cytokines Production

Rheumatoid arthritis (RA) is a chronic and debilitating autoimmune disease characterized by chronic joint inflammation with subsequent cartilage and bone destruction. RA is emerging as a model of IL-17-driven autoimmune inflammatory disease. IL-17 is a marker for Th17 cells, with its master regulator being the retinoic acid receptor-related orphan receptor (RORgammat) regulated by STAT3 signaling. Glucuronoxylomannan (GXM), a polysaccharide representing the main component of the capsular material of the opportunistic yeast Cryptococcus neoformans, exhibits potent immunosuppressive properties both in vitro and in vivo. The present study investigates the effects of GXM treatment on the progression of collagen-induced arthritis. GXM suppressed clinical signs of collagen-induced arthritis and blocked joint erosion progression. This effect was mediated by down-regulation of key cytokines involved in the pathogenesis of RA such as TNF-alpha and IL-1beta, and up-regulation of the inhibitory cytokine IL-10. Moreover, a reduction of IL-6 and TGF-beta, which inhibit Th17 differentiation with consequent decreased IL-17 production at the local and systemic level, was observed. The effect of GXM on Th17 differentiation mirrored the reduction in STAT3 activation and inhibition of RORgammat synthesis. Consequently, this work highlights the beneficial properties of an efficacious compound that could eventually be destined to the clinic.

Diversity and pharmaceutical screening of fungi from benthic mats of Antarctic lakes

During the MICROMAT project , the fungal diversity of microbial mats growing in the benthic environment of Antarctic lakes was accessed for the discovery of novel antibiotics and anticancers. In all, 160 filamentous fungi belonging to fifteen different genera and 171 yeasts were isolated from 11 lakes, classified and cultivated in different media and at different temperatures. Filamentous fungi were then screened to discover novel antimicrobial and cytotoxic compounds. A total of 1422 extracts were prepared by solid phase extraction of the culture broths or by biomass solvent extraction. 47 (29%) filamentous fungi showed antimicrobial activity; most of them inhibited the growth of gram-positive Staphyloccus aureus (14%), gram-negative E. coli (10%), and of yeasts Candida albicans (11%) and Cryptococcus neoformans (8%). Less activity was detected against representatives of enterobacteria and filamentous fungi. The most productive in terms of bioactivities were cold-tolerant cosmopolitan hyphomycetes such as Penicillium, Aspergillus, Beauveria and Cladosporium. Two bioactive bis-anthraquinones (rugulosin and skyrin) were identified by LC–MS as the main products in a strain of Penicillium chrysogenum isolated from a saline lake in the Vestfold Hills. LC–MS fractionation of extracts from two diverse species of Aspergillus, that exhibited relatively potent antimicrobial activities, evidenced a chemical novelty that was further investigated. To our knowledge, this is the first report of new antibiotics produced by fungi from benthic microbial mats from Antarctic lakes. It can be concluded that these microbial assemblages represent an extremely rich source for the isolation of new strains producing novel bioactive metabolites with the potential to be developed as drugs.

Mitracarpus frigidus aerial parts exhibited potent antimicrobial, antileishmanial, and antioxidant effects

The crude extract and the hexane, CH 2Cl 2, EtOAc, n-BuOH, and hydromethanolic fractions of the aerial parts of Mitracarpus frigidus were evaluated against promastigote forms of two species of Leishmania ( L. chagasi and L. amazonensis), 11 strains of bacteria ( Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella enterica sorovar Tythimurium, Shigella sonnei, Klebsiella pneumoniae, Escherichia coli, Micrococcus luteus, Enterococcus faecalis, Enterobacter cloacae, Streptococcus pyogenes and Bacillus cereus) and two yeasts ( Candida albicans and Cryptococcus neoformans). The antioxidant activity (DPPH radical scavenging activity and reducing power), cytotoxicity against mammalian cells, and the contents of phenolics and flavonoids were determined. Phytochemical analysis of the major groups of phytoconstituents is also reported. All samples showed antioxidant activity which was positively correlated to the content of phenolic compounds. S. sonnei, B. cereus and C. neoformans were susceptible to all extracts tested, except for the n-BuOH and hydromethanolic fractions, which demonstrated no antimicrobial activity. The lowest MIC was recorded for the CH 2Cl 2 fraction against C. neoformans (MIC of 10 μg/ml), followed by B. cereus, S. sonnei, and E. cloacae (MIC of 20, 39 and 39 μg/ml, respectively). The CH 2Cl 2 fraction was the most effective against L. chagasi (IC 50 of 6.7 μg/ml), and the hydromethanolic fraction exhibited the best activity against L. amazonensis (IC 50 of 9 μg/ml). A cytotoxic effect on mammalian cells was observed only for the crude extract and CH 2Cl 2 fraction at the concentrations of 130 and 31 μg/ml, respectively. These results suggest that M. frigidus has interesting antimicrobial, antileishmanial and antioxidant activities.