Invasive Geotrichum clavatum fungal infection in an acute myeloid leukaemia patient: a case report and review

A Repertoire of the Less Common Clinical Yeasts

Invasive fungal diseases are a public health problem. They affect a constantly increasing number of at-risk patients, and their incidence has risen in recent years. These opportunistic infections are mainly due to Candida sp. but less common or rare yeast infections should not be underestimated. These so-called "less common" yeasts include Ascomycota of the genera Candida (excluding the five major Candida species), Magnusiomyces/Saprochaete, Malassezia, and Saccharomyces, and Basidiomycota of the genera Cryptococcus (excluding the Cryptococcus neoformans/gattii complex members), Rhodotorula, and Trichosporon. The aim of this review is to (i) inventory the less common yeasts isolated in humans, (ii) provide details regarding the specific anatomical locations where they have been detected and the clinical characteristics of the resulting infections, and (iii) provide an update on yeast taxonomy. Of the total of 239,890 fungal taxa and their associated synonyms sourced from the MycoBank and NCBI Taxonomy databases, we successfully identified 192 yeasts, including 127 Ascomycota and 65 Basidiomycota. This repertoire allows us to highlight rare yeasts and their tropism for certain anatomical sites and will provide an additional tool for diagnostic management.

Infection With Saprochaete Clavata in Children After Hematopoietic Cell Transplantation

Septic shock is a very rare manifestation of invasive fungal disease (IFD) in children after allogeneic hematopoietic cell transplantation (allo-HCT). The objective of this paper is analysis of two cases of pediatric patients with IFD caused by Saprochaete clavata after allo-HCT. Literature data on this infection in children and its outcome were also summarized. Infection with Saprochaete clavate presenting with symptoms of septic shock was being reported in 4 children, and 2 of them survived the infection. In conclusion, with quick diagnosis and quick treatment, the outcome of therapy of infection with Saprochaete clavata was successful.

Saprochaete clavata invasive infection: characterization, antifungal susceptibility, and biofilm evaluation of a rare yeast isolated in Brazil

Rare emerging pathogens such as Saprochaete clavata are associated with invasive fungal diseases, high morbidity, mortality, rapidly fatal infections, and outbreaks. However, little is known about S. clavata infections, epidemiology, risk factors, treatment, biofilms, and disease outcomes. The objective of this study was to describe a new case of severe S. clavata infection in a patient diagnosed at a referral children's hospital in Brazil, including antifungal minimal inhibitory concentration, S. clavata biofilm characterization, and molecular characterization. The S. clavata isolated from an immunocompromised 11-year-old male patient was characterized using MALDI-TOF, Gram staining, scanning electron microscopy (SEM), and next generation sequencing (NGS) of genomic DNA. Biofilm production was also evaluated in parallel with determining minimal inhibitory concentration (MIC) and biofilm sensitivity to antifungal treatment. We observed small to medium, whitish, farinose, dry, filamentous margin colonies, yeast-like cells with bacillary features, and biofilm formation. The MALDI-TOF system yielded a score of ≥ 2,000, while NGS confirmed S. clavata presence at the nucleotide level. The MIC values (in mg L-1) for tested drugs were as follows: fluconazole = 2, voriconazole ≤ 2, caspofungin ≥ 8, micafungin = 2, amphotericin B = 4, flucytosine ≤ 1, and anidulafungin = 1. Amphotericin B can be active against S. clavata biofilm and the fungus can be susceptible to new azoles. These findings were helpful for understanding the development of novel treatments for S. clavata-induced disease, including combined therapy for biofilm-associated infections.

Clincial features and prognostic factors of magnusiomyces (saprochaete) infections in hematology. a multicenter study of seifem/fungiscope

BACKGROUND

Our multicenter study aims to identify baseline factors and provide guidance for therapeutic decisions regarding Magnusiomyces-associated infections, an emerging threat in patients with hematological malignancies.

METHODS

HM patients with proven M. capitatus or M. clavatus (formerly Saprochaete capitata and Saprochaete clavata) infection diagnosed between January 2010 and December 2020 were recorded from the SEIFEM (Sorveglianza Epidemiologica Infezioni nelle Emopatie) group and FungiScope (Global Emerging Fungal Infection Registry). Cases of Magnusiomyces fungemia were compared with candidemia.

RESULTS

Among 90 Magnusiomycescases (60 [66%] M. capitatus and 30 (34%) M. clavatus), median age was 50 years (range 2-78), 46 patients (51%) were female and 67 (74%) had acute leukemia. Thirty-six (40%) of Magnusiomyces-associated infections occurred during antifungal prophylaxis, mainly with posaconazole (n=13, 36%) and echinocandins (n=12, 34%). Instead, the candidemia rarely occurred during prophylaxis (p<0.0001). First-line antifungal therapy with azoles, alone or in combination, was associated with improved response compared to other antifungals (p=0.001). Overall day-30 mortality rate was 43%. Factors associated with higher mortality rates were septic shock (HR 2.696, 95%CI 1.396-5.204, p=.003), corticosteroid treatment longer than 14 days (HR 2.245, 95%CI 1.151-4.376, p=.018), and lack of neutrophil recovery (HR 3.997, 95%CI 2.102-7.601, p<.001). The latter was independently associated with poor outcome (HR 2.495, 95%CI 1.192-5.222, p=.015).

CONCLUSIONS

Magnusiomyces-associated infections are often breakthrough infections. Effective treatment regimens of these infections remain to be determined, but neutrophil recovery appears to play an important role in the favorable outcome.

Saprochaete clavata (Geotrichum clavatum) septicemia in a patient with multiple myeloma; An emerging case from Southeastern Turkey

Background and Purpose

Invasive fungal infections (IFI) are life-threatening and can be seen in immuno-compromised patients with malignancy, those who undergo chemotherapy, or transplant recipients. The Candida and Aspergillus species are the most common IFI agents; however, infections can also be caused by rare fungal species. This case report is about a bloodstream infection due to Saprochaete clavata (formerly known as Geotrichum clavatum) in a woman with multiple myeloma.

Case report

A 59-years-old woman suffered from fever, widespread rashes, and diarrhea after an autologous bone marrow transplantation. Peripheral blood cultures were taken from the patient and sent to the microbiology laboratory. Cultures grew white to cream-colored cottony colonies. Moreover, septate and branched hyphae and arthroconidia were seen under a microscope by lactophenol blue staining. The fungi colonies were identified by Maldi Biotyper 3. 1. (manufactured by Bruker Daltonics, USA) as S. clavata (G. clavatum) with a reliable score. Antifungal susceptibility test was carried out by the concentration gradient strip Etest method. Minimal inhibitory concentrations of Amphotericin B, fluconazole, voriconazole, posaconazole, and anidulafungin were determined as 4, 3, 0.125, 0.125, and &gt; 32 mg/dL, respectively. Despite amphotericin B treatment, the patient died three days after the identification of the fungi.

Conclusion

The IFIs are serious conditions that have high mortality rates. In the current case report, we aimed to draw attention to S. clavata which is a rare fungal agent.

Recent developments in less known and multi-resistant fungal opportunists

Fungal infections have increased in recent years due to host factors, such as oncohaematological and transplant-related disorders, immunosuppressive therapy, and AIDS. Additionally, molecular and proteomic facilities have become available to identify previously unrecognizable opportunists. For these reasons, reports on less-known and recalcitrant mycoses, such as those caused by black fungi, hyaline filamentous fungi, coelomycetes, Mucorales, and non-Candida yeasts have emerged. In this review, novel taxonomy in these groups, which often are multi-resistant to one or several classes of antifungals, is discussed. Clinical presentations, diagnosis and current treatment of some major groups are summarised.

Saprochaete clavata Infection in Immunosuppressed Patients: Systematic Review of Cases and Report of the First Oral Manifestation, Focusing on Differential Diagnosis

Background: Saprochaete clavata infection is an emerging issue in immunosuppressed patients, causing fulminant fungaemia. The purpose of this systematic review of cases is to retrieve all cases of S. clavata infection and describe oral lesions as the first manifestation of S. clavata infection. Methods: We report the first case of intraoral S. clavata infection in Acute Myeloid Leukemia (AML) affected subject, presenting as multiple grayish rapidly growing ulcerated swellings, and provide a review of all published cases of infection caused by S. clavata, according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, conducted by searching SCOPUS, Medline, and CENTRAL databases. Only articles in English were considered. Individual patient data were analyzed to identify risk factors for S. clavata infection. Results: Seventeen of 68 retrieved articles were included in the review reporting data on 96 patients (mean age 51.8 years, 57 males and 38 females). Most cases were disseminated (86) with a 60.2% mortality rate. Ninety-five were hematological patients, with AML being the most common (57 cases). Conclusions:S. clavata infection in immunosuppressed patients has a poor prognosis: middle-age patients, male gender and Acute Myeloid Leukemia should be considered risk factors. In immunosuppressed patients, the clinical presentation can be particularly unusual, imposing difficult differential diagnosis, as in the reported case.

Identification and antifungal susceptibility of Saprochaete clavata from invasive infections in Turkey

Saprochaete clavata is an emerging opportunistic pathogen, that causes life-threatening infections, but there are limited evidence and information about the evaluation of in vitro antifungal susceptibility test results. The aim of this study was to determine S. clavata isolates from clinical specimens and to investigate their in vitro antifungal susceptibility. S. clavata was identified by API ID20C AUX (BioMérieux, Brussels, Belgium), MALDI TOF (Bruker Daltonik, Germany), and ITS gene region sequencing. In vitro susceptibility tests were performed using Sensititre YeastOne (TREK Diagnostic System, East Grinstead, UK). During the study period, 4,736 fungi were isolated from various clinical samples and, S. clavata was identified in eight patients with underlying diseases namely, pancreatic neoplasma, acute myeloid leukaemie, follicular lymphoma, cholelithiasis. Anidulafungin and micafungin minimum inhibitory concentration values were 1-2 and 1-4 mg/L, respectively, while those of the azole group antifungals were much lower. This is the first study in Turkey reporting isolation, identification and antifungal susceptibilities of S. clavata from clinical specimens. Higher MIC values seen in some isolates suggest that continuous monitoring of sensitivity rates and observation of regional differences will thus be useful guides in determining infection control and antifungal use policies.

Invasive Saprochaete Infections: An Emerging Threat to Immunocompromised Patients

Saprochaete clavata and Saprochaete capitata are emerging fungal pathogens that are responsible for life threatening infections in immunocompromised patients, particularly in the setting of profound neutropenia. They have been associated with multiple hospital outbreaks mainly in Europe. In this article, we present a comprehensive review of the epidemiology, clinical presentation, diagnosis, antifungal susceptibility and treatment of these organisms. The diagnosis of invasive Saprochaete disease is challenging and relies primarily on the isolation of the fungi from blood or tissue samples. Both species are frequently misidentified as they are identical macroscopically and microscopically. Internal transcribed spacer sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry are useful tools for the differentiation of these fungi to a species level. Saprochaete spp. are intrinsically resistant to echinocandins and highly resistant to fluconazole. Current literature suggests the use of an amphotericin B formulation with or without flucytosine for the initial treatment of these infections. Treatment with extended spectrum azoles might be promising based on in vitro minimum inhibitory concentration values and results from case reports and case series. Source control and recovery of the immune system are crucial for successful therapy.

Stress Tolerance of Yeasts Dominating Reverse Osmosis Membranes for Whey Water Treatment

Filamentous yeast species belonging to the closely related Saprochaete clavata and Magnusiomyces spicifer were recently found to dominate biofilm communities on the retentate and permeate surface of Reverse Osmosis (RO) membranes used in a whey water treatment system after CIP (Cleaning-In-Place). Microscopy revealed that the two filamentous yeast species can cover extensive areas due to their large cell size and long hyphae formation. Representative strains from these species were here further characterized and displayed similar physiological and biochemical characteristics. Both strains tested were able to grow in twice RO-filtrated permeate water and metabolize the urea present. Little is known about the survival characteristics of these strains. Here, their tolerance toward heat (60, 70, and 80°C) and Ultraviolet light (UV-C) treatment at 255 nm using UV-LED was assessed as well as their ability to form biofilm and withstand cleaning associated stress. According to the heat tolerance experiments, the D60°C of S. clavata and M. spicifer is 16.37 min and 7.24 min, respectively, while a reduction of 3.5 to >4.5 log (CFU/mL) was ensured within 5 min at 70°C. UV-C light at a dose level 10 mJ/cm2 had little effect, while doses of 40 mJ/cm2 and upward ensured a ≥4log reduction in a static laboratory scale set-up. The biofilm forming potential of one filamentous yeast and one budding yeast, Sporopachydermia lactativora, both isolated from the same biofilm, was compared in assays employing flat-bottomed polystyrene microwells and peg lids, respectively. In these systems, employing both nutrient rich as well as nutrient poor media, only the filamentous yeast was able to create biofilm. However, on RO membrane coupons in static systems, both the budding yeast and a filamentous yeast were capable of forming single strain biofilms and when these coupons were exposed to different simulations of CIP treatments both the filamentous and budding yeast survived these. The dominance of these yeasts in some filter systems tested, their capacity to adhere and their tolerance toward relevant stresses as demonstrated here, suggest that these slow growing yeasts are well suited to initiate microbial biofouling on surfaces in low nutrient environments.

Outbreak of Saprochaete clavata Sepsis in Hematology Patients: Combined Use of MALDI-TOF and Sequencing Strategy to Identify and Correlate the Episodes

Introduction

New fungal species are increasingly reported in immunocompromised patients. Saprochaete clavata (S. clavata), an ascomycetous fungus formerly called Geotrichum clavatum, is intrinsically resistant to echinocandins and is often misidentified.

Objective

We describe a cluster of seven S. clavata infections in hospitalized hematology patients who developed this rare fungemia within a span of 11 months. Three of the seven patients died. Identification of the isolates was determined only with the Saramis database of VitekMS system and sequencing of the internal transcribed spacer (ITS) region. Clonal relatedness of the isolates was determined by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF) analysis; clonal correlation between the strains was investigated by means of phylogenetic analysis, based on single-nucleotide variants (SNPs). Clinical presentation, 1–3 β-D-glucan (BG) and galactomannan (GM) antigen results and analysis of possible sources of contamination are also described with a prospective case–control study of the outbreak.

Results

MALDI-TOF MS-Vitek (bioMerieux, Marcy l’Etoile, France) failed to identify the six isolates, while SARAMIS (bioMerieux, Marcy l’Etoile, France) identified the isolates as S. clavata. Initially, Vitek 2 identified the strains as Geotrichum capitatum in two of the seven cases. Molecular identification gave 99% homology with S. clavata. BG was positive in three out of six patients (range 159 to >523 pg/ml), GM results were always negative. All the isolates were resistant to echinocandins (anidulafungin, micafungin, and caspofungin) and Fluconazole, but susceptible to Flucytosine and Voriconazole. One isolate showed acquired resistance to Flucytosine and Amphotericin B during treatment. Both the correlation-based dendrograms obtained by MALDI-TOF MS (Bruker Daltonics) and MS-Vitek not only clustered six of the seven bloodstream infection (BSI) isolates in the same group, but also showed their strong relatedness. Phylogenetic analysis using SNPrelate showed that the seven samples recorded during the investigation period clustered together. We observed a split between one case and the remainder with a node supported by a z-score of 2.3 (p-value = 0.021) and 16 mutations unique to each branch.

Conclusion

The use of proteomics for identification and evaluation of strain clonality in outbreaks of rare pathogens is a promising alternative to laborious and time-consuming molecular methods, even if molecular whole-genome sequencing (WGS) typing will still remain the reference method for rare emergent pathogens.

Identification of medically important yeasts by sequence analysis of the internal transcribed spacer and D1/D2 region of the large ribosomal subunit

BACKGROUND

The prevalence of opportunistic yeast infections has increased in recent decades as the result of an increasing immunocompromised patient population.

AIMS

To evaluate ribosomal RNA (rRNA) gene sequence to identify medically important yeast species, to investigate the performance of both the rRNA gene internal transcribed spacer (ITS) and D1/D2 region in identifying clinically relevant yeasts, and to compare these results with those of a standard phenotypic method.

METHODS

Both regions from 50 yeast strains, comprising 45 clinical isolates and 5 reference strains, were amplified using PCR and then sequenced. The sequences were compared to reference data available from the GenBank database of the National Center for Biotechnology Information using the BLASTn tool.

RESULTS

Using ID32C, 88% (44/50) of all strains were identified accurately at the species level, although 6% were misidentified; two Candida eremophila isolates were identified as Candida glabrata and Candida tropicalis, and one Saprochaete clavata isolate was identified as Saprochaete capitata. Two of the four isolates identified by phenotypic methods as Trichosporon asahii were defined so by analyzing the ITS region, but the remaining two were not distinguishable from closely related species. Based on the D1/D2 region, these four isolates had 100% sequence identity with T. asahii, Trichosporon japonicum, and Trichosporon asteroides. The isolate identified as Trichosporon inkin using ID32C could not be distinguished from Trichosporon ovoides by analyzing the ITS and D1/D2 regions.

CONCLUSIONS

Identifying medically important yeasts by sequencing the ITS and D1/D2 region is a rapid and reliable alternative to conventional identification methods. For a diagnostic algorithm, we suggest a two-step procedure integrating conventional methods (e.g. microscopic morphology on corn meal agar with Tween® 80 and API ID32C®) and sequence analysis of the ITS and D1/D2 region.

Saprochaete clavata Invasive Infections - A New Threat to Hematological-Oncological Patients

Background

Saprochaete clavata (formerly Geotrichum clavatum, now proposed as Magnusiomyces clavatus) is a filamentous yeast-like fungus that has recently been described as an emerging pathogen mostly in patients with acute leukemia.

Methods

This is a retrospective study of patients diagnosed with proven and probable S. clavata infection at the University Hospital, Hradec Králové, Czechia between March 2005 and December 2017. Previous cases were identified from the literature and FungiScope^® database.

Results

Six new cases (5 females, 1 male) of blood-stream S. clavata infections at the hemato-oncological department were described including epidemiological data of additional 48 patients colonized with the species. Overall, 116 strains of S. clavata were isolated from different clinical specimens of 54 patients; most of them belonged to the respiratory tract (60.3%). S. clavata was the most frequent species among arthroconidial yeasts (Trichosporon, Galactomyces, Magnusiomyces) recovered from the blood. All our patients with S. clavata infection had profound neutropenia, a central venous catheter, broad-spectrum antibiotics and antifungal prophylaxis; four had a history of a biliary tract system disease. The diagnosis was based on a positive blood culture in all patients. Four patients died of multiorgan failure and sepsis despite treatment with lipid-based amphotericin B and/or voriconazole. From the literature and FungiScope database, 67 previous cases of S. clavata infections were evaluated in context of our cases.

Conclusion

Saprochaete clavata infection represents a life-threatening mycosis in severely immunocompromised patients. The successful outcome of treatment seems to be critically dependent on the early diagnosis and the recovery of underlying conditions associated with immune dysfunction or deficiency.

Saprochaete clavata infections in patients undergoing treatment for haematological malignancies: A report of a monocentric outbreak and review of the literature

Saprochaete clavata is a rare cause of fungaemia with deep organ involvement in patients with haematological malignancies with reported mortality rates of 60%-80%. We describe four cases of S clavata infection in a haematology unit over several months that were treated with voriconazole-based regimens. We also review the literature on factors that could contribute to earlier recognition and effective treatment of S clavata. We included all cases of culture-positive S clavata from sterile sites with associated signs of infection in patients undergoing treatment for a haematological malignancy. Isolates were identified by MALDI-TOF MS, and spectrum profiles were used to prepare clustering analysis of isolates. Susceptibility testing was performed using a commercial microtitre methods. Saprochaete clavata was isolated from the bloodstream in three cases and bronchial alveolar lavage (BAL) fluid in one case. Clustering analysis suggested strains of S clavata were clonal without evidence of divergence although a common source was not identified. Susceptibility testing yielded elevated MICs to fluconazole (8 mg/L) and echinocandins (>1-8 mg/L). All patients were treated with voriconazole-based regimens resulting in survival of 3/4 patients, who continued chemotherapy for their underlying malignancy without evidence of relapse. Saprochaete clavata is a rare but aggressive cause of breakthrough yeast infection in patients undergoing treatment for haematological malignancies, particularly patients with a prior history of echinocandin treatment. Timely initiation of appropriate treatment, aided by more rapid identification in microbiology laboratory, can reduce the risk of deep organ dissemination and patient death.

Invasive Fungal Infection Caused by Geotrichum clavatum in a Child with Acute Leukemia: First Documented Case from Mainland China

Invasive fungal infections are one of the vital complications among acute leukemia patients undergoing induction chemotherapy. Among them, Geotrichum clavatum infections present extremely rarely with atypical clinical symptoms which make them difficult to diagnose. In this paper, we report a case of infection caused by Geotrichum clavatum in a 10-year old child with acute leukemia, which is the first documented case from mainland China. With underlying childhood leukemia, the child suffered from recurrent bacterial and fungal infection and even underwent abdominal surgery during the treatment. Fortunately, the therapeutic effect was finally achieved by adjusting the treatment program to dual anti-fungal treatment with micafungin and amphotericin B. Information regarding the epidemiological, clinical, and therapeutic features, in this case, shows significant perspectives for anti-fungal treatment for immunocompromised individuals, wherefore the rate of recovery and survival can be achieved.

Emerging infections due to filamentous fungi in humans and animals: only the tip of the iceberg?

Over the last few decades, the number of patients susceptible to invasive filamentous fungal infections has steadily increased, especially in populations suffering from hematological diseases. The pathogens responsible for such mycoses are now quite well characterized, such as Aspergillus spp. - the most commonly isolated mold -, Mucorales, Fusarium spp., Scedosporium spp. or melanized fungi. An increase in the incidence of this category of 'emerging' fungi has been recently highlighted, evoking a shift in fungal ecology. Starting from these medical findings, taking a step back and adopt a wider perspective offers possible explanations of this phenomenon on an even larger scale than previously reported. In this review, we illustrate the link between emerging fungi in medicine and changes in ecology or human behaviours, and we encourage integrative approaches to apprehend the adverse effects of progress and develop preventive measures in vast domains, such as agriculture or medicine.

A cluster of Geotrichum clavatum (Saprochaete clavata) infection in haematological patients: a first Italian report and review of literature

Invasive fungal infections, usually Aspergillus and Candida, represent a major cause of morbidity and mortality in patients with malignant haematological diseases, but in the last years rare fungal infections have more frequently been reported. Here, we report the clinical history of three patients affected with haematological malignancies who developed an infection caused by Geotrichum (G.) clavatum. Two out of three patients were affected by acute myeloid leukaemia (AML), and one by mantle cell lymphoma (MCL). All patients received cytarabine-based chemotherapeutic regimens and developed G. clavatum infection within 3 weeks from therapy initiation. In all cases, G. clavatum was isolated from central venous catheter and peripheral blood cultures. In vitro susceptibility test confirmed an intrinsic resistance to echinocandins and, in all cases, visceral localisations (spleen, liver and lung) were documented by total body computed tomography (CT) scan. A prolonged antifungal therapy with high doses liposomal amphotericin-B was necessary to obtain fever resolution. Only the patient with MCL died while the other two AML recovered, and one of them after received an allogeneic stem cell transplantation. We consecutively reviewed all published cases of infection caused by G. clavatum. Our experience and literature review indicate that G. clavatum can cause invasive infection in haematological patients, mainly in those with acute leukaemia.

Saprochaete clavata invasive infection in a patient with severe aplastic anemia: Efficacy of voriconazole and liposomal amphotericin B with adjuvant granulocyte transfusions before neutrophil recovery following allogeneic bone marrow transplantation

We report a case of a 27-year old man with severe aplastic anemia who developed a Saprochaete clavata (Geotrichum clavatum) disseminated invasive infection shortly prior a scheduled allogeneic bone marrow transplantation. Treatment with a combination of voriconazole, liposomal amphotericin B and adjuvant granulocyte transfusions was successful before neutrophil recovery.

The roles of sexual and asexual reproduction in the origin and dissemination of strains causing fungal infectious disease outbreaks

Sexual reproduction commonly refers to the reproductive process in which genomes from two sources are combined into a single cell through mating and then the zygote genomes are partitioned to progeny cells through meiosis. Reproduction in the absence of mating and meiosis is referred to as asexual or clonal reproduction. One major advantage of sexual reproduction is that it generates genetic variation among progeny which may allow for faster adaptation of the population to novel and/or stressful environments. However, adaptation to stressful or new environments can still occur through mutation, in the absence of sex. In this review, we analyzed the relative contributions of sexual and asexual reproduction in the origin and spread of strains causing fungal infectious diseases outbreaks. The necessity of sex and the ability of asexual fungi to initiate outbreaks are discussed. We propose a framework that relates the modes of reproduction to the origin and propagation of fungal disease outbreaks. Our analyses suggest that both sexual and asexual reproduction can play critical roles in the origin of outbreak strains and that the rapid spread of outbreak strains is often accomplished through asexual expansion.