Differentiation between isolates of Aspergillus fumigatus from breeding turkeys and their environment by genotyping with microsatellite markers

Avian-associated Aspergillus fumigatus displays broad phylogenetic distribution, no evidence for host specificity, and multiple genotypes within epizootic events

Birds are highly susceptible to aspergillosis, which can manifest as a primary infection in both domestic and wild birds. Aspergillosis in wild birds causes mortalities ranging in scale from single animals to large-scale epizootic events. However, pathogenicity factors associated with aspergillosis in wild birds have not been examined. Specifically, it is unknown whether wild bird-infecting strains are host-adapted (i.e. phylogenetically related). Similarly, it is unknown whether epizootics are driven by contact with clonal strains that possess unique pathogenic or virulence properties, or by distinct and equally pathogenic strains. Here, we use a diverse collection of Aspergillus fumigatus isolates taken from aspergillosis-associated avian carcasses, representing 24 bird species from a wide geographic range, and representing individual bird mortalities as well as epizootic events. These isolates were sequenced and analyzed along with 130 phylogenetically diverse human clinical isolates to investigate the genetic diversity and phylogenetic placement of avian-associated A. fumigatus, the geographic and host distribution of avian isolates, evidence for clonal outbreaks among wild birds, and the frequency of azole resistance in avian isolates. We found that avian isolates were phylogenetically diverse, with no clear distinction from human clinical isolates, and no sign of host or geographic specificity. Avian isolates from the same epizootic events were diverse and phylogenetically distant, suggesting that avian aspergillosis is not contagious among wild birds and that outbreaks are likely driven by environmental spore loads or host comorbidities. Finally, all avian isolates were susceptible to Voriconazole and none contained the canonical azole resistance gene variants.

Modelling the effect of pH and water activity in the growth of Aspergillus fumigatus isolated from corn silage

AIMS

The aim of this work was to use mathematical kinetic modelling to assess the combined effects of a_W, pH, O₂ availability and temperature on the growth rate and time to growth of Aspergillus fumigatus strains isolated from corn silage.

METHODS AND RESULTS

A full factorial design was used in which two factors were assayed: pH and a_W . The a_W levels assayed were 0·80, 0·85, 0·90, 0·92, 0·94, 0·96, 0·98 and 0·99. The levels of pH assayed were 3·5, 4, 4·5, 5, 6, 7, 7·5 and 8. The assay was performed at normal oxygen tension at 25 and 37°C, and at reduced oxygen tension at 25°C. Two strains of A. fumigatus isolated from corn silage were used. Kinetic models were built to predict growth of the strain under the assayed conditions. The cardinal models gave a good quality fit for radial growth rate data. The results indicate that the environmental conditions which take place during silage production, while limiting the growth of most micro-organisms, would not be able to control A. fumigatus. Moreover, pH levels in silage, far from limiting its growth, are also close to its optimum. Carbon dioxide at 5% in the environment did not significantly affect its growth.

CONCLUSIONS

A need for a further and controlled acidification of the silage exists, as no growth of A. fumigatus was observed at pH 3·5, as long as the organoleptic characteristics of the silage are not much compromised.

SIGNIFICANCE AND IMPACT OF THE STUDY

Aspergillus fumigatus is one of the major opportunistic pathogens able to cause illness such as allergic bronchopulmonary aspergillosis, aspergilloma and invasive aspergillosis to rural workers. Exposure of animals to A. fumigatus spores can result in infections, particularly in those organs exposed to external invasion, such as the airways, mammary gland and uterus at birth.

Identification and characterization of Aspergillus fumigatus isolates from broilers

Abstract: Aspergillosis is one of the main causes of mortality in birds. The pulmonary system is most frequently affected, with lesions observed in the air sacs and lungs of a wide variety of bird species. The aim of this study was to confirm by molecular methods the identification and the genetic diversity of Aspergillus fumigatus isolates of lung's samples from healthy broilers (Galus galus domesticus). Forty-four (9.5%) isolates of lung's samples were confirmed as A. fumigatus by polymerase chain reaction (PCR) multiplex (amplification of β-tub and rodA gene fragments). Microsatellite typing for A. fumigatus was used to analyse all avian isolates. Among them, 40 genotypes (90.9%) were observed only one time. The results showed a high variability and multiple genotypes of de A. fumigatus collected from lung's samples of broilers.

Immunochemical analysis of fumigaclavine mycotoxins in respiratory tissues and in blood serum of birds with confirmed aspergillosis

The ergoline alkaloid fumigaclavine A (FuA) is one of the major mycotoxins produced by Aspergillus fumigatus, the main causative fungal agent of avian aspergillosis. To study in situ production of FuA, post-mortem respiratory tissues of various avian species, as well as blood samples of falcons (Falco sp.), were analysed by enzyme immunoassay (EIA). At a detection limit of 1.5 ng/ml, FuA EIA positive results were obtained for tissue samples from seven (64%) out of 11 birds with confirmed aspergillosis, with a maximum concentration of 38 ng/g, while all controls (n = 7) were negative. No FuA could be detected in blood serum (detection limit 0.7 ng/ml) of 15 falcons, experimentally inoculated with A. fumigatus conidia. Fungal mycelium material from tissue of clinical aspergillosis cases, cultured on malt extract agar, was highly positive in the FuA EIA in milligrams per gram range. Chromatographic analysis of mycelium extracts revealed the co-presence of FuA and the structurally related fumigaclavine C (FuC). Alkaline hydrolysis of FuA and FuC yielded the corresponding deacetylation products, FuB and FuE. This is the first report showing that fumigaclavine alkaloids are produced by A. fumigatus in situ during the course of clinical aspergillosis in birds; however, the role of these compounds in the pathogenesis of this disease is still unknown.

Aspergillus and aspergilloses in wild and domestic animals: a global health concern with parallels to human disease

The importance of aspergillosis in humans and various animal species has increased over the last decades. Aspergillus species are found worldwide in humans and in almost all domestic animals and birds as well as in many wild species, causing a wide range of diseases from localized infections to fatal disseminated diseases, as well as allergic responses to inhaled conidia. Some prevalent forms of animal aspergillosis are invasive fatal infections in sea fan corals, stonebrood mummification in honey bees, pulmonary and air sac infection in birds, mycotic abortion and mammary gland infections in cattle, guttural pouch mycoses in horses, sinonasal infections in dogs and cats, and invasive pulmonary and cerebral infections in marine mammals and nonhuman primates. This article represents a comprehensive overview of the most common infections reported by Aspergillus species and the corresponding diseases in various types of animals.

Genetic and virulence variation in an environmental population of the opportunistic pathogen Aspergillus fumigatus

Environmental populations of the opportunistic pathogen Aspergillus fumigatus have been shown to be genotypically diverse and to contain a range of isolates with varying pathogenic potential. In this study, we combined two RAPD primers to investigate the genetic diversity of environmental isolates from Manchester collected monthly over 1 year alongside Dublin environmental isolates and clinical isolates from patients. RAPD analysis revealed a diverse genotype, but with three major clinical isolate clusters. When the pathogenicity of clinical and Dublin isolates was compared with a random selection of Manchester isolates in a Galleria mellonella larvae model, as a group, clinical isolates were significantly more pathogenic than environmental isolates. Moreover, when relative pathogenicity of individual isolates was compared, clinical isolates were the most pathogenic, Dublin isolates were the least pathogenic and Manchester isolates showed a range in pathogenicity. Overall, this suggests that the environmental population is genetically diverse, displaying a range in pathogenicity, and that the most pathogenic strains from the environment are selected during patient infection.

Aspergillus fumigatus from normal and condemned carcasses with airsacculitis in commercial poultry

Carcass inspection is important for the detection of certain diseases and for monitoring their prevalence in slaughterhouses. The objective of this study was to assess the occurrence of aspergillosis caused by Aspergillus fumigatus in commercial poultry, through mycological and histopathological diagnosis, and to verify the causal association between the aspergillosis diagnosis criteria and condemnation due to airsacculitis in broilers through a case-control study. The study was carried out with 380 samples. Lungs were collected from broilers that were condemned (95) or not condemned (285) due to airsacculitis directly from the slaughter line. Forty-six (12%) lung samples were positive for A. fumigatus in mycological culture. Among all samples, 177 (46.6%) presented histopathological alterations, with necrotic, fibrinous, heterophilic pneumonia; heterophilic pneumonia and lymphoid hyperplasia being the most frequent. Out of the 380 lungs analyzed, 65.2% (30) showed histopathological alterations and isolation of fungi. The statistical analysis (McNemar's chi-square test) indicated a significant association between the presence of histopathological lesions and the isolation of A. fumigatus. Mycological cultivation and histopathological diagnosis increase the probability of detecting pulmonary alterations in birds condemned by the Final Inspection System, which suggests that such diagnostic criteria can improve the assessment and condemnation of birds affected by airsacculitis.

Microsatellite typing of Aspergillus flavus from clinical and environmental avian isolates

Aspergillosis is one of the most common causes of death in captive birds. Aspergillus fumigatus accounts for approximately 95 % of aspergillosis cases and Aspergillus flavus is the second most frequent organism associated with avian infections. In the present study, the fungi were grown from avian clinical samples (post-mortem lung material) and environmental samples (eggs, food and litter). Microsatellite markers were used to type seven clinical avian isolates and 22 environmental isolates of A. flavus. A. flavus was the only species (28 % prevalence) detected in the avian clinical isolates, whereas this species ranked third (19 %) after members of the genera Penicillium (39 %) and Cladosporium (21 %) in the environmental samples. Upon microsatellite analysis, five to eight distinct alleles were detected for each marker. The marker with the highest discriminatory power had eight alleles and a 0.852 D value. The combination of all six markers yielded a 0.991 D value with 25 distinct genotypes. One clinical avian isolate (lung biopsy) and one environmental isolate (egg) shared the same genotype. Microsatellite typing of A. flavus grown from avian and environmental samples displayed an excellent discriminatory power and 100 % reproducibility. This study showed a clustering of clinical and environmental isolates, which were clearly separated. Based upon these results, aspergillosis in birds may be induced by a great diversity of isolates.

Genetic structure of Aspergillus flavus populations in human and avian isolates

Aspergillus flavus is the second leading cause of allergic, invasive, and colonizing fungal diseases in humans, and also the second most frequent organism associated with avian infections. Currently, it is not known whether there is a link between the environmental isolates and/or human isolates of A. flavus and those responsible for aspergillosis in birds. Microsatellite typing was used to analyze 29 A. flavus clinical and environmental avian isolates and 63 human clinical isolates collected from patients with a variety of aspergillosis diseases. The combination of all six markers yielded 77 different genotypes with a 0.98 D value. A. flavus genotypes obtained from avian isolates were compared with those obtained from human clinical and environmental samples. The standardized indices of association I (A) and rBarD were significantly different from zero (p < 0.01), suggesting a prevailing clonal reproduction. There was high genetic diversity between the hospital and poultry environments of A. flavus isolates. The human environmental population was significantly differentiated from environmental and clinical avian populations (F (st) > 0.25). The avian clinical subpopulation exchanged few strains with the environmental human (N (m) = 7.24) and avian (N (m) = 6.60) populations. The minimum spanning tree analysis identified three A. flavus genotype clusters that were highly structured according to the isolation source (p < 10(-4)).

Molecular epidemiology of Aspergillus fumigatus: an in-depth genotypic analysis of isolates involved in an outbreak of invasive aspergillosis

We recently reported an outbreak of invasive aspergillosis in the major heart surgery unit of Hospital Gregorio Marañón, Madrid, Spain (T. Peláez, P. Muñoz, J. Guinea, M. Valerio, M. Giannella, C. H. W. Klaassen, and E. Bouza, Clin. Infect. Dis., in press). Aspergillus fumigatus was isolated from clinical samples from 10 patients admitted to the unit during the outbreak period (surgical wound invasive aspergillosis, n = 2; probable pulmonary invasive aspergillosis, n = 4; colonization, n = 4). In the study described here, we have studied the genotypic diversity of the A. fumigatus isolates found in the air and clinical samples. We used short tandem repeats of A. fumigatus (STRAf) typing to analyze the genotypes found in the 168 available A. fumigatus isolates collected from the clinical samples (n = 109) from the patients and from the environmental samples taken from the air of the unit (n = 59). The genotypic variability of A. fumigatus was higher in environmental than in clinical samples. Intrasample variability was also higher in environmental than in clinical samples: 2 or more different genotypes were found in 26% and 89% of clinical and environmental samples, respectively. We found matches between environmental and clinical isolates in 3 of the 10 patients: 1 patient with postsurgical invasive aspergillosis and 2 patients with probable pulmonary invasive aspergillosis. A total of 7 genotypes from 3 different patients and the air grouped together in 2 clusters. Clonally related genotypes and microvariants were detected in both clinical and environmental samples. STRAf typing proved to be a valuable tool for identifying the source of invasive aspergillosis outbreaks and for studying the genotypic diversity of clinical and environmental A. fumigatus isolates.

Aspergillus fumigatus in Poultry

Aspergillus fumigatus remains a major respiratory pathogen in birds. In poultry, infection by A. fumigatus may induce significant economic losses particularly in turkey production. A. fumigatus develops and sporulates easily in poor quality bedding or contaminated feedstuffs in indoor farm environments. Inadequate ventilation and dusty conditions increase the risk of bird exposure to aerosolized spores. Acute cases are seen in young animals following inhalation of spores, causing high morbidity and mortality. The chronic form affects older birds and looks more sporadic. The respiratory tract is the primary site of A. fumigatus development leading to severe respiratory distress and associated granulomatous airsacculitis and pneumonia. Treatments for infected poultry are nonexistent; therefore, prevention is the only way to protect poultry. Development of avian models of aspergillosis may improve our understanding of its pathogenesis, which remains poorly understood.

Simple and highly discriminatory microsatellite-based multiplex PCR for Aspergillus fumigatus strain typing

The answers to important questions concerning Aspergillus fumigatus pathogenicity, transmissions routes and efficacy of treatments require highly discriminating and reproducible genotyping methods. The present study was aimed at improving microsatellite methodology for A. fumigatus typing by reducing the task of strain identification to a single multiplex reaction and by selecting highly accurate short tandem repeat polymorphisms. A set of eight primer pairs was used for the genotype determination of 116 clinical isolates of A. fumigatus obtained from three healthcare centres. A new, automated and highly discriminatory typing method is described for A. fumigatus strains. The optimized multiplex PCR was successfully performed with all tested clinical strains and showed a discriminatory power of 0.9997 among presumably unrelated isolates. The comparison of groups of strains from different health centres showed that 99.6% of the genotypic variation was present within groups. Strains with the same genotype were isolated from the same patient, sometimes recovered more than 1 year later. A few cases of patients at the same clinic unit carrying strains of identical genotype strongly suggested colonization by A. fumigatus during their hospitalization. Specific measures must therefore be taken in order to prevent and restrict such incidents.

Effects of conidia of various Aspergillus species on apoptosis of human pneumocytes and bronchial epithelial cells

Aspergillus species can cause mycoses in human and animals. Previously, we demonstrated that A. fumigatus conidia from a human isolate inhibited apoptosis in human pneumocytes and bronchial epithelial cells. In the current study, we studied the effects of A. fumigatus conidia non-human origin and A. flavus, A. nidulans, A. niger and A. oryzae conidia on human cells apoptosis. Human pneumocytes or bronchial epithelial cells were simultaneously exposed to apoptotic inductors and aspergilli conidia. The cell cultures were analyzed by flow cytometry, immunoblotting, and examination of nuclear morphology. Similar to A. fumigatus conidia, A. flavus conidia inhibited cellular apoptosis while A. nidulans, A. niger and A. oryzae conidia did not affect apoptosis. We further studied the species specificity of conidia: there were no differences in the inhibition of apoptosis by A. fumigatus conidia from either human or bird isolates. In order to determine whether the inhibition of apoptosis by conidia is limited to certain strains, the effect on human cell apoptosis of different A. fumigatus human clinical isolates and A. fumigatus of environmental origin was evaluated. All A. fumigatus isolates inhibited apoptosis; an anti-apoptotic factor was released by conidia. For TNF-induced apoptosis, the anti-apoptotic effect of conidia of all isolates was found to be associated with a reduction of caspase-3 in human cells. The results suggest that suppression of apoptosis may play a role in reducing the efficacy of host defense mechanisms during infection with Aspergillus species.

Clinical, mycological and pathological findings in turkeys experimentally infected byAspergillus fumigatus

Experimental aspergillosis was induced in 1-day-old turkeys by intra-air-sac inoculation of a spore suspension of a 3-day-old Aspergillus fumigatus culture (CBS 144.89) containing 10(7) spores. Ten additional poults were used as controls. Infected and non-infected animals were closely observed at least twice a day for the appearance of clinical signs and were sequentially sacrificed at days 1, 2, 3, 5 and 7 post-inoculation. In the infected group, most lung tissues and air sac swabs were culture positive from day 1 to day 5. At 1 day post-inoculation, air sac membranes were multifocally and moderately to severely thickened by an oedema and covered by an exudate. A small number of germinating conidia were present in the superficial exudate, already giving rise to small radiating hyphae. Lung lesions were mild, dominated by a diffuse congestion and a mild heterophilic infiltration. From 2 to 3 days post-inoculation, air sac membranes were more severely affected and several granulomas were observed. Both granulomas and exudates were rich in germinated conidia and hyphae. Pulmonary lesions consisted in a diffuse pneumonia. Five days post-inoculation, air sac membrane lesions progressed to a severe, multifocal, heterophilic and granulomatous inflammation. Seven days post-inoculation, a reduction of the severity of the diffuse pneumonia was detected. Concomitantly, the fungal elements were mainly observed as fragmented tubules in the cytoplasm of multinucleate giant cells. The present study demonstrated that healthy turkey poults might be able to withstand exposure to 10(7) A. fumigatus spores.

Verruculogen associated with Aspergillus fumigatus hyphae and conidia modifies the electrophysiological properties of human nasal epithelial cells

Background

The role of Aspergillus fumigatus mycotoxins in the colonization of the respiratory tract by conidia has not been studied extensively, even though patients at risk from invasive aspergillosis frequently exhibit respiratory epithelium damage. In a previous study, we found that filtrates of A. fumigatus cultures can specifically alter the electrophysiological properties of human nasal epithelial cells (HNEC) compared to those of non pathogenic moulds.

Results

We fractionated the organic phase of filtrate from 3-day old A. fumigatus cultures using high-performance liquid chromatography. The different fractions were tested for their ability to modify the electrophysiological properties of HNEC in an in vitro primary culture model.

The fraction collected between 20 and 30 min mimicked the effects of the whole filtrate, i.e. decrease of transepithelial resistance and increase of potential differences, and contained secondary metabolites such as helvolic acid, fumagillin, and verruculogen. Only verruculogen (10^-8 M) had effects similar to the whole filtrate. We verified that verruculogen was produced by a collection of 67 human, animal, plant and environmental A. fumigatus isolates. Using MS-MS analysis, we found that verruculogen was associated with both mycelium and conidia extracts.

Conclusion

Verruculogen is a secondary metabolite that modifies the electrophysiological properties of HNEC. The role of these modifications in the colonization and invasion of the respiratory epithelium by A. fumigatus on first contact with the epithelium remains to be determined.

ATIVIDADE “IN VITRO” DE TRÊS AGENTES QUÍMICOS FRENTE A DIFERENTES ESPÉCIES DE ASPERGILLUS

RESUMO A aspergilose é causada por fungos ubíquos e oportunistas do gênero Aspergillus, que liberam milhares de conídios no ar, contaminando o ambiente, sendo de extrema importância a utilização de filtros de ar e programas corretos de anti-sepsia e desinfecção para prevenção da enfermidade. Este estudo avaliou a eficácia “in vitro” dos agentes químicos, iodóforo, amônia quaternária e clorexidina, frente a isolados de Aspergillus fumigatus (8), Aspergillus niger (8), Aspergillus flavus (6) e Aspergillus terreus (1). Para o teste foram preparadas diluições sucessivas dos desinfetantes/antisépticos (log2) em caldo RPMI, e os inóculos foram ajustados até uma concentração final de 5 x 104 UFC/mL. Foi realizada a técnica de microdiluição em caldo de acordo com NCCLS M-38, adaptada para agentes químicos, com incubação das microplacas a 35° C em agitação constante. A leitura visual dos resultados foi realizada após 96 horas, e os isolados de Aspergillus spp. utilizados foram resistentes ao iodóforo nas concentrações testadas. A amônia quaternária e a clorexidina mostraram-se eficazes contra os isolados de Aspergillus spp., com exceção de um A. fumigatus e um A. terreus. Com estes resultados indica-se a utilização da amônia quaternária e da clorexidina na prevenção da aspergilose, questionando-se o uso de iodóforos para este fim.

Phenotypic and genotypic identification of human pathogenic aspergilli

Human pathogenic aspergilli are identified in the clinical diagnostic laboratory predominantly by macro- and micro-morphology. Such phenotypic characteristics are largely subjective and unstable, as they are influenced by environmental factors, including media and temperature of incubation. Recent advances in molecular biology have impacted the field of mycology; multiple studies have noted new genetically distinct species that are not easily distinguished by phenotypic characteristics. Strengths of molecular typing methods include objectivity and the ability to identify nonsporulating or slowly growing fungi. As such, molecular methods provide powerful tools for the study of the epidemiology, evolution and population biology of fungal pathogens. This review focuses on current and future methods of identifying aspergilli, and implications regarding Aspergillus species/strain identification.

Evolution of the Environmental Contamination by Thermophilic Fungi in a Turkey Confinement House in France

Fungal species constitute a major part of environmental contaminants in facilities where animals are housed. The present investigation was aimed at describing the relative abundances of fungal species and their concentrations in a turkey confinement house in France. Fungal cultures from poultry feed, litter, and air were undertaken every week throughout the 16-wk period of breeding. The incubation temperature of 40 degrees C was selected to isolate thermophilic fungal species (especially Aspergillus spp. and Candida albicans) that are potentially pathogenic for birds. The 2 species Aspergillus fumigatus and Aspergillus flavus were recovered at a mean of 10.5 and 37.0 cfu/m(3) of air sampled, respectively. Individual samplings yielded concentrations of up to 150.0 cfu/m(3) for A. flavus in the first weeks of the investigation. Other fungal species were recovered at a mean of 18.9 cfu/m(3) (maximum 36.3 cfu/m(3)) in the air. The yeast C. albicans was first detected at wk 4 from litter samples and at wk 7 from poultry feed. Densities of C. albicans remained very high in litter samples (63.2 cfu/g) even after new litter was added at wk 10. To analyze the genetic polymorphism of A. fumigatus, the most pathogenic mold in birds, a total number of 198 isolates (134 from air, 34 from litter, and 30 from feed samples) were genotyped using 2 polymorphic microsatellite markers. More than half (42 out of 73, 57.5%) of the genotypes were detected only once. This finding suggests that the contamination of the breeding environment is not due to a single source and confirms the very high genetic diversity of environmental A. fumigatus isolates. As during the study period, no outbreak of fungal infections occurred; the levels of fungal contaminations reported here do not seem sufficient, at least alone, to trigger fungal infections.

Aspergillosis in Larus cachinnans micaellis: Survey of Eight Cases

Avian aspergillosis is reported in several avian species, with Aspergillus fumigatus as the main aetiological agent. Predisposing factors such as starvation, thermal stress, migratory stress, primary infectious disease or toxicosis may play a role. Eight cases of disseminated aspergillosis in free ranging seagulls sheltered at C.R.U.M.A. (Centro Recupero Uccelli Marini e Acquatici, Livorno, Italy) with different clinical histories are presented. The infection was demonstrated by cultural and histological methods from lesions of all birds, and the presence of airborne A. fumigatus viable elements ranging from 450 to 525 CFU/m(3) inside and outside the shelter by means of a surface air sampler (SAS) Super-90 was also assessed. The role of this fungal species as an opportunistic factor in the captivity of seagulls is considered and some control measures, such as a clean and stress free environment and the use of antifungal drugs are suggested.

Molecular typing of aspergilli: Recent developments and outcomes

Aspergillus spp. have been the subject of numerous epidemiological studies. The most useful typing techniques are DNA based methods including the random amplified polymorphic DNA technique, microsatellite length polymorphisms, restriction fragment length polymorphism (RFLP) analysis using retrotransposon-like sequences as probes, and multilocus sequence typing. The results of typing clinical isolates indicate that most of the invasive aspergillosis (IA) patients were infected by a single strain. Genetic analysis could not discriminate between clinical and environmental isolates of Aspergillus. fumigatus, indicating that every strain present in the environment is a potential pathogen if it encounters the appropriate host. The source of infection can also be monitored by typing. Typing studies led to the discovery of a new pathogenic species, A. lentulus, and to the identification of several species not known previously to be pathogenic. Typing studies revealed the existence of two genetically isolated groups within a global A. fumigatus population. Aspergillus fumigatus was found to be the first example of a true cosmopolitan fungus. Additionally, the results obtained in several studies support the premise that recombination played an important role in A. fumigatus populations. The discovery of functional mating type genes in A. fumigatus indicates that past or recent sexual processes could be responsible for the observed recombining population structure.

Microsatellite marker analysis as a typing system for Candida glabrata

Candida glabrata is one of the most important causes of nosocomial fungal infection. We investigated, using a multiplex PCR, three polymorphic microsatellite markers, RPM2, MTI, and ERG3, in order to obtain a rapid genotyping method for C. glabrata. One set of primers was designed for each locus, and one primer of each set was dye labeled to read PCR signals using an automatic sequencer. Eight reference strains including other Candida species and 138 independent C. glabrata clinical isolates were tested. The clinical isolates were collected from different anatomical sites of adult patients either hospitalized in different wards of two different hospitals or not hospitalized. Since C. glabrata is haploid, one single PCR product for each PCR set was obtained and assigned to an allele. The numbers of different alleles were 5, 7, and 15 for the RPM2, MTI, and ERG3 loci, respectively. The number of allelic associations was 21, leading to a discriminatory power of 0.84. The markers were stable after 25 subcultures, and the amplifications were specific for C. glabrata. A factorial correspondence analysis did not indicate any correlation between the 21 multilocus genotypes and the clinical data (source, sex, ward, anatomical sites). Microsatellite marker analysis is a rapid and reliable technique to investigate clinical issues concerning C. glabrata. However, its discriminatory power should be improved by testing other polymorphic microsatellite loci.

Fungal virulence, vertebrate endothermy, and dinosaur extinction: is there a connection?

Fungi are relatively rare causes of life-threatening systemic disease in immunologically intact mammals despite being frequent pathogens in insects, amphibians, and plants. Given that virulence is a complex trait, the capacity of certain soil fungi to infect, persist, and cause disease in animals despite no apparent requirement for animal hosts in replication or survival presents a paradox. In recent years studies with amoeba, slime molds, and worms have led to the proposal that interactions between fungi and other environmental microbes, including predators, select for characteristics that are also suitable for survival in animal hosts. Given that most fungal species grow best at ambient temperatures, the high body temperature of endothermic animals must provide a thermal barrier for protection against infection with a large number of fungi. Fungal disease is relatively common in birds but most are caused by only a few thermotolerant species. The relative resistance of endothermic vertebrates to fungal diseases is likely a result of higher body temperatures combined with immune defenses. Protection against fungal diseases could have been a powerful selective mechanism for endothermy in certain vertebrates. Deforestation and proliferation of fungal spores at cretaceous-tertiary boundary suggests that fungal diseases could have contributed to the demise of dinosaurs and the flourishing of mammalian species.