Aspergillus fumigatus

University of SulaimaniBiology departmentPractical Mycology

Dashty Latif

Sarko Ibrahim

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Species: fumigatus

Genus: Aspergillus

Family:Trichocomaceae

Order: Eurotiales

Class: Eurotiomycetes

Phylum: Ascomycota

Kingdom: Fungi

Scientific classification

aspergillum, which resembled the genus-characteristic conidia-forming structure of these fungi. Aspergillus is an extremely diverse and widely distributed genus of filamentous ascomycete fungi. It includes over 200 species of mostly asexual fungi found ubiquitously In soil as well as in forage products, food, dust, organic debris, and decomposing vegetation. Being supreme opportunists, the aspergilli have adapted to various chemical, physical, and biological stresses and have repeatedly changed their lifestyle and reproductive mode in the course of evolution. While most of them are thought to be saprophytes.The Aspergillin number of species are able to infect wounded plants and animals. The advent of immunosuppressive agents and other medical advances created a new biological niche for aspergilli, the immunocompromised human host.

Introduction

A. nidulans – may be amphotericin B resistant

The genus Aspergillus – ~180 species,

38 have caused disease (able to grow at 37C)

Common in the environment

A. nigerA. terreus – resistant to AmBA. flavus -sometimes amphotericin B resistant

www.aspergillus.org.uk

A. fumigatus low frequency of azole resistance

Aspergillus fumigatus

conidial head

What is aspergillus fumigatus?

Aspergillus fumigatus is a fungus of the genus Aspergillus, and is one of the most common Aspergillus species to cause disease in individuals with an immunodeficiency.A. fumigatus, a saprotroph widespread in nature, is typically found in soil and decaying organic matter, where it plays an essential role in carbon and nitrogen recycling. A. fumigatus is a well-known pathogenic fungusthat is responsible for more than 80% of aspergillosis,especially in immunocompromised patients.A. fumigatus has 23 allergenic proteins.hermotolerance – Ability to thrive at ≥ 37°C.Ability to sense and utilize nutrients in different forms and from difference sources.

Sputum Cultures for Fungus

Bacteriological media inferior to fungal media – 32% higher yield on fungal

media

A four day A. fumigatus culture on malt extract agar (above). Light microscopy pictures are taken at 1000x, stained with lacto-phenol cotton blue.

Structure of A. fumigatus. On the surface of the expanded apical region are a series of

spore-bearing cells called phialides. Repeated mitotic division in the phialide nucleus yields a chain of asexual spores usually called conidiospores or conidia. The conidiospore varies in shape from spherical to elongate and may be smooth or echinulate. Conidia are extremely hydrophobic and are easily dispersed by air. Modern taxonomic works also rely on characteristics of the whole colony (color, size, presence or absence of scle- rotia and pigments) when strains are grown under standardized culture conditions (Klich 2002; Samson, Hong et al. 2006). Figure 1.1 is an example of typical Aspergillus conidia and a conidiophore.

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AspergillosisAspergillosis is a spectrum of diseases in humans and animals caused by members of the genus Aspergillus.Aspergillus is a fungus whose spores are present in the air we breathe, but does not normally cause illness.usually occurs in people with lung diseases or weakened immune systems. The spectrum of illness includes allergic reactions, lung infections, and infections in other organs.(1) Mycotoxicosis due to ingestion of contaminated foods (2) Allergy and sequelae to the presence of conidia or transient

growth of the organism in body orifices(3) Colonization without extension in preformed cavities and

debilitated tissues(4) Invasive, inflammatory, granulomatous, necrotizing

disease of lungs, and other organs (5) Systemic and fatal disseminated disease.

CLASSIFICATION OF ASPERGILLOSIS

Persistence without disease - colonisation of the airways or nose/sinuses

Airways/nasal exposure to airborne Aspergillus

Invasive aspergillosis• Acute (<1 month course)• Subacute/chronic necrotising (1-3 months)

Chronic aspergillosis (>3 months)• Chronic cavitary pulmonary• Aspergilloma of lung• Chronic fibrosing pulmonary• Chronic invasive sinusitis • Maxillary (sinus) aspergilloma

Allergic• Allergic bronchopulmonary (ABPA)• Extrinsic allergic (broncho)alveolitis (EAA)• Asthma with fungal sensitisation• Allergic Aspergillus sinusitis (eosinophilic fungal rhinosinusitis)

Invasive pulmonary aspergillosis

www.aspergillus.org.uk

Normal lungIPA

IPA occurs in ~7% of acute leukaemia patients, 10-15% allogeneic BMT patients

Aspergillus Secondary Metabolitesaflatoxin

as a cause of human liver cancers. Acute human afl atoxin poisoning, however, is rare and usu- ally only occurs when starvation forces people to subsist on moldy foods.

Lovastatin

While Aspergillus infections and toxins detract from the quality of human life, some of the products of Aspergillus metabolism have made positive contributions to the human health as drugs.

Aspergillus fumigatus is exceptional among microorganisms in being both a primary and oppor- tunistic pathogen as well as a major allergen. Its conidia production is prolifi c, and so human respiratory tract exposure is almost constant. A. fumigatus is isolated from human habitats and vegetable c ompost heaps. In immunocompromised individuals, the incidence of invasive infection can be as high as 50% and the mortality rate is often about 50%. The interaction of A. fumigatus and other a irborne fungi with the immune system is increasingly linked to severe asthma and sinusitis (Nierman, Pain et al. 2005). British physician John Hughes Bennett is credited with the fi rst published description of an Aspergillus infection, an aspergilloma (“fungus ball”) in 1842. Subsequently, it has been learned that most asper- gillomas are caused by A. fumigatus, which is a thermotolerant species often resident in compost heaps. (Brakhage and Langfelder 2002). It is one of the most common airborne fungi, and humans and other animals regularly inhale numerous conidia. In healthy organisms, the respiratory tract eliminates these spores. For decades A. fumigatus was c onsidered a weak pathogen, associated mostly with allergic condi- tions such as “farmer’s lung” and bronchopulmonary aspergillosis (Latge 1999). The fi rst case of inva- sive human aspergillosis, in an immunocompromised patient, was made in 1953.

Allergic bronchopulmonary aspergillosis usually is found associated with asthma and cystic fi brosis. Some patients experience little permanent loss of respiratory function while others develop irreversible, obstructive lung diseases.

Allergic bronchopulmonary aspergillosis usually is found associated with asthma and cystic fi brosis. Some patients experience little permanent loss of respiratory function while others develop irreversible, obstructive lung diseases.

he species is only known to reproduce by asexual means, but there has been accumulating evidence for recombination and gene flow from population genetic studies, genome analysis, the presence of mating-type genes and expression of sex-related genes in the fungus. Here we show that A. fumigatus possesses a fully functional sexual reproductive cycle that leads to the production of cleistothecia and ascospores, and the teleomorph Neosartorya fumigata is described. The species has a heterothallic breeding system; isolates of complementary mating types are required for sex to occur. We demonstrate increased genotypic variation resulting from recombination between mating type and DNA fingerprint markers in ascospore progeny from an Irish environmental subpopulation. The ability of A. fumigatus to engage in sexual reproduction is highly significant in understanding the biology and evolution of the species. The presence of a sexual cycle provides an invaluable tool for classical genetic analyses and will facilitate research into the genetic basis of pathogenicity and fungicide resistance in A. fumigatus, with the aim of improving methods for the control of aspergillosis. These results also yield insights into the potential for sexual reproduction in other supposedly ‘asexual’ fungi.

Life cycle

The first known human exploitation of Aspergillus for beneficial purposes was for the transformation of rice, soybeans, and other plant foods to improve their palatability and to make them available for further fermentation by yeasts and bacteria. The domestication of Aspergillus for food production is thought to have originated in China close to 2000 years ago. Subsequently, similar food fermentations were adopted in Indonesia, Japan, Korea, and other parts of Asia. Koji is the Japanese name for mold- fermented grains and/or soybeans.

Beneficial of A. fumigatus

References

http://www.aspergillus.org.ukhttp://www.cdc.gov/fungal/aspergillosis/http://www.nature.com/nature/journal/v457/n7228/full/nature07528.htmlhttp://www.who.int/bulletin/volumes/89/12/11-089441/en/http://en.wikipedia.org/wiki/Aspergillus_fumigatusO'Gorman CM et al. (2008). "Discovery of a sexual cycle in the opportunisticfungal pathogen Aspergillus fumigatus“. Nature 457 (7228): 471–4.