Characterization of multiple isolates of Aspergillus fumigatus from patients: genotype, mating type and invasiveness

Phytochemical analysis and anti-infective potential of fungal endophytes isolated from Nigella sativa seeds

Endophytic fungi, particularly from higher plants have proven to be a rich source of antimicrobial secondary metabolites. The purpose of this study is to examine the antimicrobial potential of three endophytic fungi Aspergillus sp. SA1, Aspergillus sp. SA2, and Aspergillus sp. SA3, cultivated from Nigella sativa seeds against Staphylococcus aureus (ATCC 9144), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Klebsiella pneumoniae (ATCC 13883), MRSA (ATCC 33591), and human pathogen Candida albicans (ATCC 10231). Furthermore, the most active cultivated endophytic fungi were molecularly identified via internal transcribed spacer (ITS) sequencing. HR-ESIMS guided approach has been used successfully in chemical profiling of 26 known bioactive secondary metabolites (1-26), which belongs to different classes of natural compounds such as polyketides, benzenoids, quinones, alcohols, phenols or alkaloids. Finally, in-silico interactions within active site of fungal Cyp51 and bacterial DNA gyrase revealed possibility of being a hit-target for such metabolites as antimicrobials.

Potential Implication of Azole Persistence in the Treatment Failure of Two Haematological Patients Infected with Aspergillus fumigatus

Invasive aspergillosis (IA) is a major cause of morbidity and mortality in patients receiving allogeneic haematopoieticcell transplantation. The deep immunosuppression and a variety of potential additional complications developed in these patients result in IA reaching mortality rates of around 50-60%. This mortality is even higher when the patients are infected with azole-resistant isolates, demonstrating that, despite the complexity of management, adequate azole treatment can have a beneficial effect. It is therefore paramount to understand the reasons why antifungal treatment of IA infections caused by azole-susceptible isolates is often unsuccessful. In this respect, there are already various factors known to be important for treatment efficacy, for instance the drug concentrations achieved in the blood, which are thus often monitored. We hypothesize that antifungal persistence may be another important factor to consider. In this study we present two case reports of haematological patients who developed proven IA and suffered treatment failure, despite having been infected with susceptible isolates, receiving correct antifungal treatment and reaching therapeutic levels of the azole. Microbiological analysis of the recovered infective isolates showed that the patients were infected with multiple strains, several of which were persisters to voriconazole and/or isavuconazole. Therefore, we propose that azole persistence may have contributed to therapeutic failure in these patients and that this phenomenon should be considered in future studies.

Phenotypic Variants of Azole-Resistant Aspergillus Fumigatus that Co-exist in Human Respiratory Samples are Genetically Highly Related

Respiratory specimens obtained from patients with chronic forms of aspergillosis contain phenotypic variants of azole-resistant Aspergillus fumigatus (ARAF) that co-exist in the airway. Here we aimed to study whether phenotypic variants of ARAF that co-exist in clinical specimens were genetically distinct. A panel of six phenotypic variants of ARAF cultured from two sputum samples collected from two patients with chronic aspergillosis were included. Preliminary identification of all isolates was obtained using MALDI–ToF mass spectrometry and confirmed by AsperGenius^® real-time PCR assay. Antifungal susceptibility testing was determined using EUCAST E.Def 9.3 microbroth dilution. Genomic DNA libraries were constructed with the Illumina TruSeq Nano kit. Prepared whole-genome libraries were sequenced on an Illumina HiSeq 2500. Whole genome data were converted into presence/absence of a SNP with respect to the Af293 reference genome. Colonies of ARAF that co-existed in one respiratory sample demonstrated marked phenotypic diversity. Two cyp51A polymorphisms were found among azole-resistant isolates: TR₃₄/L98H/T289A/I364V/G448S was consistently present in four variants with a pan-azole resistant phenotype and TR₃₄/L98H was detected in two variants (itraconazole MIC > 16 mg/L). WGS typing showed that despite marked phenotypic variation, each sample contained a population of highly genetically related azole-resistant A. fumigatus variants. Our SNP analysis suggest that mechanisms additional to genetic-based variation are responsible for phenotypic diversity. Our data demonstrate that the phenotypic variants of ARAF that co-exist in clinical specimens are highly clonal and strongly suggest their origination from a single common ancestor.

Deciphering Aspergillus fumigatus cyp51A-mediated triazole resistance by pyrosequencing of respiratory specimens

Background

Infections caused by triazole drug-resistant Aspergillus fumigatus are an increasing problem. The sensitivity of standard culture is poor, abrogating susceptibility testing. Early detection of resistance can improve patient outcomes, yet tools for this purpose are limited.

Objectives

To develop and validate a pyrosequencing technique to detect resistance-conferring cyp51A polymorphisms from clinical respiratory specimens and A. fumigatus isolates.

Methods

Method validation was performed by Sanger sequencing and pyrosequencing of 50 A. fumigatus isolates with a spectrum of triazole susceptibility patterns. Then, 326 Aspergillus quantitative PCR (qPCR)-positive respiratory samples collected over a 27 month period (January 2017–March 2019) from 160 patients at the UK National Aspergillosis Centre were assessed by cyp51A pyrosequencing. The Sanger sequencing and pyrosequencing results were compared with those from high-volume culture and standard susceptibility testing.

Results

The cyp51A genotypes of the 50 isolates analysed by pyrosequencing and Sanger sequencing matched. Of the 326 Aspergillus qPCR-positive respiratory specimens, 71.2% were reported with no A. fumigatus growth. Of these, 56.9% (132/232) demonstrated a WT cyp51A genotype and 31.5% (73/232) a resistant genotype by pyrosequencing. Pyrosequencing identified the environmental TR34/L98H mutation in 18.7% (61/326) of the samples in contrast to 6.4% (21/326) pan-azole resistance detected by culture. Importantly, pyrosequencing detected resistance earlier than culture in 23.3% of specimens.

Conclusions

The pyrosequencing assay described could detect a wide range of cyp51A polymorphisms associated with triazole resistance, including those not identified by commercial assays. This method allowed prompt recognition of resistance and the selection of appropriate antifungal treatment when culture was negative.

Molecular Epidemiology of Aspergillus fumigatus in Chronic Pulmonary Aspergillosis Patients

Molecular fungal genotyping techniques developed and employed for epidemiological studies have understandably concentrated on establishing the genetic diversity of Aspergillus fumigatus in invasive aspergillosis due to its severity, the urgency for treatment, and the need to demonstrate possible sources. Some early studies suggested that these strains were phenotypically, if not genotypically, different from others. However, with improved discrimination and evaluations, incorporating environmental as well as clinical isolates from other Aspergillus conditions (e.g., chronic pulmonary aspergillosis and cystic fibrosis), this premise is no longer upheld. Moreover, with the onset of increased global triazole resistance, there has been a concerted effort to incorporate resistance profiling into genotyping studies and the realisation that the wider population of non-immunocompromised aspergillosis patients are at risk. This review summarises the developments in molecular genotyping studies that incorporate resistance profiling with attention to chronic pulmonary aspergillosis and an example of our UK experience.

Mixed infection by Histoplasma capsulatum isolates with different mating types in Brazilian AIDS-patients

Mixed infection by Histoplasma capsulatum isolates with different mating types, in AIDS-patients are described in this study. Morphological, mating type-specific PCR assay and multilocus sequencing type analysis of H. capsulatum isolates recovered from two Brazilian AIDS-patients were performed. Five H. capsulatum isolates were recovered at different times from the two patients. Three isolates were obtained from bone marrow (day 1 – CE0411) and buffy coat cultures (day 1 – CE0311; day 2 – CE0511) of patient 1, and two isolates were isolated from buffy coat cultures (day 3 – CE2813; day 12 – CE2513) of patient 2. The mycelial colonies depicted different textures and pigmentation features. Dimorphic conversion to the yeast-phase in ML-Gema medium was achieved in all isolates. MAT1-1 idiomorph was identified in CE0311, CE0411 and CE2813 isolates; MAT1-2 idiomorph was found in CE0511 and CE2513 isolates. These H. capsulatum isolates were grouped within LAm A clade, highlighting that CE0311 and CE0411 isolates formed a subgroup supported by a high bootstrap value. The CE0511, CE2513, and CE2813 isolates clustered together with a Brazilian H151 isolate. This research reports mixed infections caused by H. capsulatum isolates with different mating types in Brazilian AIDS-patients for the first time in the literature.

Could the determination of Aspergillus fumigatus mating type have prognostic value in invasive aspergillosis?

A clear link between mating type and virulence has been demonstrated for some fungal pathogens, but not for Aspergillus fumigatus as of yet. An association between mating type and invasiveness has recently been established. The mating type proportion (MAT1-1:MAT1-2) of 213 A. fumigatus strains was determined (48.5%:51.5%) and results were in agreement with previous studies. However, these percentages changed when the strain collection was divided into azole-susceptible and -resistant strains. The 163 susceptible strains kept these proportions, but among the 50 azole-resistant strains 60.0% MAT1-1 and 40% MAT1-2 were found. Moreover, looking at the clinical outcome associated to 27 azole-resistant strains, we found that MAT1-1 was linked to a high mortality rate (64%), whereas the rate associated to MAT1-2 genotype was markedly lower (15%). The pathogenicity linked to the Mat type was tested in a Galleria mellonella model of infection, showing that MAT1-1 strains were consistently more pathogenic than MAT1-2, independently of their susceptibility phenotype. This data would suggest that A. fumigatus mating type determination at the time of diagnosis could have a prognostic value in invasive aspergillosis.

Investigating Clinical Issues by Genotyping of Medically Important Fungi: Why and How?

Genotyping studies of medically important fungi have addressed elucidation of outbreaks, nosocomial transmissions, infection routes, and genotype-phenotype correlations, of which secondary resistance has been most intensively investigated. Two methods have emerged because of their high discriminatory power and reproducibility: multilocus sequence typing (MLST) and microsatellite length polymorphism (MLP) using short tandem repeat (STR) markers. MLST relies on single-nucleotide polymorphisms within the coding regions of housekeeping genes. STR polymorphisms are based on the number of repeats of short DNA fragments, mostly outside coding regions, and thus are expected to be more polymorphic and more rapidly evolving than MLST markers. There is no consensus on a universal typing system. Either one or both of these approaches are now available for Candida spp., Aspergillus spp., Fusarium spp., Scedosporium spp., Cryptococcus neoformans, Pneumocystis jirovecii, and endemic mycoses. The choice of the method and the number of loci to be tested depend on the clinical question being addressed. Next-generation sequencing is becoming the most appropriate method for fungi with no MLP or MLST typing available. Whatever the molecular tool used, collection of clinical data (e.g., time of hospitalization and sharing of similar rooms) is mandatory for investigating outbreaks and nosocomial transmission.

Invasive mould infections in the ICU setting: complexities and solutions

Infections caused by filamentous fungi represent a major burden in the ICU. Invasive aspergillosis is emerging in non-neutropenic individuals with predisposing conditions, e.g. corticosteroid treatment, chronic obstructive pulmonary disease, liver cirrhosis, solid organ cancer, HIV infection and transplantation. Diagnosis is challenging because the signs and symptoms are non-specific, and initiation of additional diagnostic examinations is often delayed because clinical suspicion is low. Isolation of an Aspergillus species from the respiratory tract in critically ill patients, and tests such as serum galactomannan, bronchoalveolar lavage 1-3-β-d-glucan and specific PCR should be interpreted with caution. ICU patients should start adequate antifungal therapy upon suspicion of invasive aspergillosis, without awaiting definitive proof. Voriconazole, and now isavuconazole, are the drugs of choice. Mucormycosis is a rare, but increasingly prevalent disease that occurs mainly in patients with uncontrolled diabetes mellitus, immunocompromised individuals or previously healthy patients with open wounds contaminated with Mucorales. A high proportion of cases are diagnosed in the ICU. Rapidly progressing necrotizing lesions in the rhino-sinusal area, the lungs or skin and soft tissues are the characteristic presentation. Confirmation of diagnosis is based on demonstration of tissue invasion by non-septate hyphae, and by new promising molecular techniques. Control of underlying predisposing conditions, rapid surgical resection and administration of liposomal amphotericin B are the main therapeutic actions, but new agents such as isavuconazole are a promising alternative. Patients with mucormycosis receive a substantial part of their care in ICUs and, despite advances in diagnosis and treatment, mortality remains very high.

Ecology of aspergillosis: insights into the pathogenic potency of Aspergillus fumigatus and some other Aspergillus species

Fungi of the genus Aspergillus are widespread in the environment. Some Aspergillus species, most commonly Aspergillus fumigatus, may lead to a variety of allergic reactions and life-threatening systemic infections in humans. Invasive aspergillosis occurs primarily in patients with severe immunodeficiency, and has dramatically increased in recent years. There are several factors at play that contribute to aspergillosis, including both fungus and host-related factors such as strain virulence and host pulmonary structure/immune status, respectively. The environmental tenacity of Aspergilllus, its dominance in diverse microbial communities/habitats, and its ability to navigate the ecophysiological and biophysical challenges of host infection are attributable, in large part, to a robust stress-tolerance biology and exceptional capacity to generate cell-available energy. Aspects of its stress metabolism, ecology, interactions with diverse animal hosts, clinical presentations and treatment regimens have been well-studied over the past years. Here, we synthesize these findings in relation to the way in which some Aspergillus species have become successful opportunistic pathogens of human- and other animal hosts. We focus on the biophysical capabilities of Aspergillus pathogens, key aspects of their ecophysiology and the flexibility to undergo a sexual cycle or form cryptic species. Additionally, recent advances in diagnosis of the disease are discussed as well as implications in relation to questions that have yet to be resolved.

Monitoring of bacterial pathogens at workplaces in power plant using biochemical and molecular methods

Purpose

The aim of this study was to characterize the ways of spreading of the most common bacterial species isolated from workers as well as from the air and raw materials at the workplaces in power plant utilizing biomass sources. To monitor microbial transmission and identify the source of contamination in the working environment, a combination of molecular and biochemical methods was applied.

Methods

The study was carried out at workplaces in power plant utilizes biomass as a main fuel source. At each of the studied workplaces, bioaerosol particles were collected on sterile Teflon filters using personal conical inhalable samplers (CIS), and biomass samples (straw pellets and briquettes, corn briquettes, sunflower pellets and wood chips) were directly taken from their storage places. Simultaneously with that, the swab samples from the hands of ten workers and their used respiratory masks (of FFP2 class) were also collected after the work shift to evaluate individual workers’ microbial contamination. In all collected samples, total bacterial concentrations were assessed and the most common microbial isolates were identified to the species level using both biochemical (API tests) and molecular polymerase chain reaction (PCR), followed by random amplification of polymorphic DNA (RAPD) typing methods.

Results

The mean concentrations of culturable bacteria in the air and in biomass samples at the studied workplaces were high, i.e. 1.2 × 10⁶cfu/m³ and 3.8 × 10⁴cfu/g, respectively. The number of bacteria in the swab and mask samples also reached a high level of 1.4 × 10⁴ cfu/ml and 1.9 × 10³ cfu/cm², respectively. Among the most frequently isolated microorganisms from all types of samples were Gram-positive bacteria of the genus Bacillus and Staphylococcus xylosus. 37 bacterial strains belonging to the genus Bacillus (B. licheniformis 8, B. pumilus 15 and B. subtilis 4) and Staphylococcus (10) were genotyped by the RAPD-PCR method. Based on RAPD-PCR analyses, the genomic similarity among 19 Bacillus strains isolated from biomass, air, protective mask and hand samples as well as 6 S. xylosus strains isolated from air, mask and hand samples exceeded 80%.

Conclusion

This study demonstrated that biomass is the primary source of bacteria at power plant workplaces. These results also revealed that biomass-associated bacteria can be easily transferred to workers’ hands and mask during their routine activities. To improve health protection at the workplaces, adequate training courses on hand hygiene and how to use and remove respiratory masks correctly for workers should be introduced as a key element of the prevention strategy. From the occupational point of view, the PCR-based methods seem to be an efficient tool for a fast and precise typing of bacterial strains isolated from different sources in the occupational environment. Such methods may help to implement appropriate prophylactic procedures and minimize transmission of infectious agents at workplaces.

Genotyping and antifungal susceptibility testing of multiple Malassezia pachydermatis isolates from otitis and dermatitis cases in pets: is it really worth the effort?

A total of 216 colonies of Malassezia pachydermatis from 28 cases of fungal otitis or dermatitis in pets were genotyped by M13 fingerprinting and tested for antifungal susceptibility. A huge genetic diversity was found (157 M13 types in total), with all animals having a polyclonal pattern of infection (5.4 ± 1.5 genotypes/sample). Furthermore, analysis of molecular variance (AMOVA) revealed that most genetic diversity (44%) was found at the within sample level. In contrast, variability in antifungal susceptibility among isolates from the same sample was less important, with different M13 types displaying in most cases identical or very similar MIC results. Most isolates displayed high in vitro susceptibility to amphotericin B, terbinafine and all azoles tested except fluconazole, for which MIC values were always ≥4 μg/ml and a 26.9% of isolates displayed values ≥32 μg/ml. We conclude that although characterization of multiple yeast isolates results in a considerable increase in laboratory workload and expenses, it may help to get a better understanding of the epidemiology of M. pachydermatis in a given patient population.

Genetic Analysis Using an Isogenic Mating Pair of Aspergillus fumigatus Identifies Azole Resistance Genes and Lack of MAT Locus's Role in Virulence

Invasive aspergillosis (IA) due to Aspergillus fumigatus is a major cause of mortality in immunocompromised patients. The discovery of highly fertile strains of A. fumigatus opened the possibility to merge classical and contemporary genetics to address key questions about this pathogen. The merger involves sexual recombination, selection of desired traits, and genomics to identify any associated loci. We constructed a highly fertile isogenic pair of A. fumigatus strains with opposite mating types and used them to investigate whether mating type is associated with virulence and to find the genetic loci involved in azole resistance. The pair was made isogenic by 9 successive backcross cycles of the foundational strain AFB62 (MAT1-1) with a highly fertile (MAT1-2) progeny. Genome sequencing showed that the F₉MAT1-2 progeny was essentially identical to the AFB62. The survival curves of animals infected with either strain in three different animal models showed no significant difference, suggesting that virulence in A. fumigatus was not associated with mating type. We then employed a relatively inexpensive, yet highly powerful strategy to identify genomic loci associated with azole resistance. We used traditional in vitro drug selection accompanied by classical sexual crosses of azole-sensitive with resistant isogenic strains. The offspring were plated under varying drug concentrations and pools of resulting colonies were analyzed by whole genome sequencing. We found that variants in 5 genes contributed to azole resistance, including mutations in erg11A (cyp51A), as well as multi-drug transporters, erg25, and in HMG-CoA reductase. The results demonstrated that with minimal investment into the sequencing of three pools from a cross of interest, the variation(s) that contribute any phenotype can be identified with nucleotide resolution. This approach can be applied to multiple areas of interest in A. fumigatus or other heterothallic pathogens, especially for virulence associated traits.

Invasive aspergillosis (IA) caused by Aspergillus fumigatus is increasing due to medical interventions that suppress the ability of patients’ immune systems to control infections. These invasive lung infections are difficult to diagnose and consequently treatment is frequently not started promptly. Some controversy surrounds the role of mating type in virulence of A. fumigatus and the emergence of azole resistant strains has posed difficult challenges for clinical management of IA. We generated nearly identical A. fumigatus strains with opposite mating types that allowed us to test whether different mating types have different virulence profiles. We found no difference in virulence in three different animal models, which suggests that mating type does not influence virulence. We also took advantage of the essentially identical genomes of both strains to apply classical genetic approaches combined with genomics technologies to identify A. fumigatus genes that contribute to azole resistance. We performed genetic crosses of azole sensitive with azole resistant strains and analyzed the resistance status and genome composition of the offspring. Using this approach we cataloged several genes that were not previously associated with azole resistance. This information will be valuable for finding ways to manage azole resistance in IA patients.

Phylogenetic analyses on the diversity of Aspergillus fumigatus sensu lato based on five orthologous loci

One hundred isolates of Aspergillus fumigatus sensu lato mainly from China, as well as from Australia, France, India, Indonesia, Ireland, UK, and USA were analyzed to infer their sequence types (STs) and population diversity based on partial calmodulin, calcineurin regulatory subunit B, beta-tubulin, cytochrome C and calcineurin catalytic subunit A genes as well as their mating types, using ClonalFrame, Structure and MEGA software. Our results inferred 48 STs and showed that most of the STs or lineages evolved independently and without clear population structure among them. Whereas one lineage was recognized that could be a true population and in which one clade might diverge into another distinct lineage, namely, a cryptic species, A. neoellipticus. In addition, we found that mutation, parasexual, and sexual recombination could, respectively, play specific roles in the evolution of these fungi. Our results also showed that MAT1-1/MAT1-2 mating type ratios of A. fumigatus sensu lato was biased to nearly 1:1.4 (20/28) when clone-corrected, but when not clone-corrected, the ratio of MAT1-1/MAT1-2 was so biased as near 1:2 (35/65), which might mean that isolates with MAT1-2 are in the process of losing sexual ability preceding those with MAT1-1.

CSP typing of Chinese Aspergillus fumigatus isolates: identification of additional CSP types

Cell surface protein (CSP) typing is a typing strategy that employs comparative DNA sequence analysis of the 12-mer tandem repeat region of the AFUA_3G08890 gene. The CSP typing scheme and modified nomenclature was applied to a collection of 162 clinical Aspergillus fumigatus isolates from China. A total of 16 CSP variants were observed, including five that were newly reported, indicating that phylogeographic differences may exist between the Chinese and the previously studied Australian, European and North American A. fumigatus populations. However, the most common CSP variants observed in this study are consistent with those in previous studies.

Azole preexposure affects the Aspergillus fumigatus population in patients

The relationship between the azole preexposure of 86 patients and the genotype, azole susceptibility, and cyp51A polymorphisms of 110 corresponding Aspergillus fumigatus isolates was explored. Isolates carrying serial polymorphisms (F46Y and M172V with or without N248T with or without D255E with or without E427K) had higher itraconazole MICs (P = 0.04), although <2 μg/ml using the EUCAST methodology, were associated with two genetic clusters (P < 0.001) and with voriconazole preexposure of patients (P = 0.016). Voriconazole preexposure influences the distribution of A. fumigatus isolates with selection of isolates carrying cyp51A polymorphisms and higher itraconazole MICs.

Occurrence and characteristics of group 1 introns found at three different positions within the 28S ribosomal RNA gene of the dematiaceous Phialophora verrucosa: phylogenetic and secondary structural implications

BACKGROUND

Group 1 introns (ribozymes) are among the most ancient and have the broadest phylogenetic distribution among the known self-splicing ribozymes. Fungi are known to be rich in rDNA group 1 introns. In the present study, five sequences of the 28S ribosomal RNA gene (rDNA) regions of pathogenic dematiaceous Phialophora verrucosa were analyzed using PCR by site-specific primers and were found to have three insertions, termed intron-F, G and H, at three positions of the gene. We investigated the distribution of group 1 introns in this fungus by surveying 34 strains of P. verrucosa and seven strains of Phialophora americana as the allied species.

RESULTS

Intron-F's (inserted at L798 position) were found in 88% of P. verrucosa strains, while intron-G's (inserted at L1921) at 12% and intron-H's (inserted at L2563) at 18%. There was some correlation between intron distribution and geographic location. In addition, we confirmed that the three kinds of introns are group 1 introns from results of BLAST search, alignment analysis and Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). Prediction of secondary structures and phylogenetic analysis of intron sequences identified introns-F and G as belonging to subgroup IC1. In addition, intron-H was identified as IE.

CONCLUSION

The three intron insertions and their insertion position in the 28S rDNA allowed the characterization of the clinical and environmental isolates of P. verrucosa and P. americana into five genotypes. All subgroups of introns-F and G and intron-H were characterized and observed for the first time in both species.

[Sexuality and pathogenicity in Aspergillus fumigatus: is there any relationship?]

BACKGROUND

Aspergillus fumigatus, like many other fungal species of clinical relevance, has been traditionally regarded as an asexual organism. However, in last few years several pieces of evidence question this such assumption, suggesting that the sexual state of A. fumigatus may still be undiscovered. These investigations have finally led to the recent discovery of a teleomorph stage of A. fumigatus, which has been named Neosartorya fumigata.

AIMS

To review the most important findings on A. fumigatus sexuality and discuss the possible implications of such findings on its pathogenicity.

METHODS

A bibliographic search was performed to find the main works that study the sexuality of fungal pathogens and, especially, of A. fumigatus. Moreover, data from our recent investigations in this field were also introduced to the discussion.

RESULTS

The existence of a teleomorph for A. fumigatus could have significant clinical repercussions, as sexual reproduction might produce offspring with increased virulence and/or resistance to antifungal agents. In this sense, the results of our investigations suggest the existence of an association between the MAT1-1 mating type and the invasiveness of A. fumigatus isolates.

CONCLUSIONS

The study of the sexual reproduction of the fungal pathogens and its possible relationship with virulence will continue to be a topic of interest during the next years, not only because of its basic interest, but also for the possible clinical repercussions.