aspergillus and aspergillosis (2)
DESCRIPTION
Aspergillus and AspergillosisTRANSCRIPT
Aspergillus and Aspergillosis
Dr Summiya Nizamuddin
A filamentous or mould form of fungus which is a vegetative growth of filaments.
– reproduction is by spores or conidia– conidia are borne on specialized hyphae or
conidiophores– Many moulds can be identified by
the morphology of these spores and by their arrangement on the hyphae
Mould• Multicellular form of fungus
• Microscopic: Septate hyphae Spores
• Macroscopic: Surface texture: Cottony/wooly/ velvety/ granular
:Pigmentation: observed from the reverse
Mould-Definitions
• Hyphae• Mycelium: a. Vegetative
b. Aerial
Mould identification
• Macroscopic characteristics: colonial form, surface color, pigmentation
• Microscopic appearance: fruiting bodies, appendages, spore shape and arrangement
Hyaline Hyphomycetes
• Hyaline Hyphomycetes include those conidial fungi which are – not darkly pigmented, – colonies may be colorless or brightly colored.
• Include the agents of hyalohyphomycosis: Aspergillosis, dermatophytosis and the dimorphic pathogens, like Histoplasma capsulatum
Hyaline Hyphomycetes include:
• Acremonium• Aspergillus• Beauveria• Chrysosporium• Cylindrocarpon• Fusarium• Geotrichum• Gliocladium• Graphium• Madurella
•Malbranchea•Onychocola•Paecilomyces•Penicillium•Scedosporium•Scopulariopsis•Sepedonium•Trichoderma•Trichothecium•Verticillium
0 hr 2 hrs 6- 8hrs14- 22 hrs
Asexual life cycle of Aspergillus
Conidium Germinating conidia
Germling Branched,multinucleate mycelium
Foot cell and vesicle
Conidiophore with conidia
Aspergillus
Colony colors in Aspergillus
Colony colors in Aspergillus
Image Courtesy: Dr. Lindsley
Conidiophore Structure
Aspergillosis
Aspergillosis- a spectrum of diseases of humans and animals caused by members of the genus Aspergillus
Disease spectrumAspergillosis includes:
(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) colonisation without extension in preformed cavities
and debilitated tissues; (4) invasive, inflammatory, granulomatous, narcotising
disease of lungs, and other organs; and rarely (5) systemic and fatal disseminated disease.
The type of disease and severity depends upon:• the physiologic state of the host and • the species of Aspergillus involved
The etiological agents are cosmopolitan and include Aspergillus fumigatus, A. flavus, A. niger, A. nidulans and A. terreus.
Ecology Found in cellars, potted plants, pepper and spices Found all over the world – Antarctica and Sahara Primary ecological niche – decaying vegetable matter
Sources of Infection? Soil Air, spores may be inhaled Water / storage tanks in hospitals etc Food Compost and decaying vegetation Fire proofing materials Bedding, pillows Ventilation and air conditioning systems Computer fans
Bennett, Medical Mycology, 2009
Aerosolized conidia
Aspergillus hyphae in the lung
Cavitary lesion A. fumigatus
culture in vitro
Aspergillus sp.–cellular states
Aspergillus Identification Criteria
Macro-morphology
Colony color
Micro-morphology
Laboratory diagnosis:1. Clinical material: Sputum, bronchial washings and tracheal aspirates from patients with pulmonary disease and tissue
biopsies from patients with disseminated disease.
2. Direct Microscopy: (a) Sputum, washings and aspirates make wet mounts in
either 10% KOH & Parker ink or Calcofluor and/or Gram stained smears;
(b) Tissue sections should be stained with H&E, GMS and PAS digest. Note Aspergillus hyphae may be missed in H&E stained sections. Examine specimens for dichotomously branched, septate hyphae.
• Interpretation:• The presence of hyaline, branching septate hyphae, consistent
with Aspergillus in any specimen, from a patient with supporting clinical symptoms should be considered significant.
• Biopsy and evidence of tissue invasion is of particular importance.
• Remember direct microscopy or histopathology does not offer a specific identification of the causative agent.
3. Culture: Clinical specimens should be inoculated onto primary isolation media, like Sabouraud's dextrose agar. Colonies are fast growing and may be white, yellow, yellow-brown, brown to black or green in colour.
• Interpretation: • Aspergillus species are well recognised as common
environmental airborne contaminants, therefore a positive culture from a non-sterile specimen, such as sputum, is not proof of infection.
• However, the detection of Aspergillus (especially A. fumigatus and A. flavus) in sputum cultures, from patients with appropriate predisposing conditions, is likely to be of diagnostic importance and empiric antifungal therapy should be considered.
• Unfortunately, patients with invasive pulmonary aspergillosis, often have negative sputum cultures making a lung biopsy a prerequisite for a definitive diagnosis.
4. Serology: Immunodiffusion tests for the detection of antibodies to Aspergillus species have proven to be of value in the diagnosis of allergic, aspergilloma, and invasive aspergillosis.
However, they should never be used alone, and must be correlated with other clinical and diagnostic data.
5. Identification: Aspergillus colonies are usually fast growing, white, yellow, yellow-brown, brown to black or shades of green, and they mostly consist of a dense felt of erect conidiophores.
• Conidiophores terminate in a vesicle covered with either a single palisade-like layer of phialides (uniseriate) or a layer of subtending cells (metulae) which bear small whorls of phialides (the so-called biseriate structure).
• The vesicle, phialides, metulae (if present) and conidia form the conidial head.
• Conidia are one-celled, smooth- or rough-walled, hyaline or pigmented, forming long dry chains which may be divergent (radiate) or aggregated in compact columns (columnar). Some species may produce Hülle cells or sclerotia.
AspergillumA perforated containerfor sprinkling holy water
Sprinkling the world with spores
Conidiophore Structure
columnar radiate
• Most species sporulate within 7 days. Descriptions are primarily based on colony pigmentation and morphology of the conidial head.
• • Microscopic mounts are best made using a
cellotape flag or slide culture preparation mounted in lactophenol cotton blue.
• Key Features: Hyaline hyphomycete showing distinctive conidial heads with flask-shaped phialides arranged in whorls on a vesicle.
• Aspergillus flavus• Aspergillus fumigatus• Aspergillus nidulans• Aspergillus niger• Aspergillus terreus
Aspergillus flavus
Deep green to olive green colonies
Dark brown to black sclerotia sometimes present
Conidial heads radiate to columnar
Stipe walls roughened
Vesicles spherical
Largely biseriate
Conidia globose to ellipsoidal
Aspergillus fumigatus
Aspergillus niger
Black to very dark brown
Rare sclerotia
Conidial heads radiate
Smooth walled stipes
Spherical vesicles
Biseriate
Globose, rough conidia
Aspergillus terreus
Brownish orange colonies
Conidial heads columnar
Smooth walled stipes
Spherical vesicles
Smooth walled globose conidia
Globose accessory conidia produced laterally on submerged hyphae
A. nidulans
Image Courtesy: Mycology online
Hülle cells Emericella nidulansCleistothecium of Emericella nidulans