Hyaline Fungi

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Hyaline

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septated, colorless/light hyphae

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Dermatophyte

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hyaline (colorless) hyphae: Hydrolyzes keratin

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Characteristic of Hyaline Fungi

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• Saprophytic
• opportunistic
• does not grow on cycloheximide
• Mold colonies generally fuzzy
• Slow growth 1 day to 4 weeks

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Mass of hyphae

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mycelium

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sporangiospores

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reproductive conidia

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Phialides

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special structures that produce biserate or uniserate conidia

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Conidiophore

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• specialized hyphal extension that supports the fruiting head from which conidia are produced
  
• Thread like
  

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Hyalohyphomycosis

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• Mycotic infection caused by a hyaline fungi
• acute invasive illness associated with immunocompromised
• Prolonged granulocytopenia
• receiving antibiotics for fever

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Mycetoma

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• Clinical syndrome characterized tumefaction, draining sinuses, and sclerotic
• Both hyaline and dematiaceous
• Hyaline: Acremonium falciforme and Aspergillus nidulans (white
• Dematiaceous: Exophilala jeanselmei and Leptosphaeria senegalensis (black) and Pseudoallesheria boydii (yellow

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Pulmonary Aspergillosis

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• Aspergilloma or fungus ball area of damaged lung (cavity)
• Fatigue, weight loss, hemoptysis

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Allergic Aspergillosis

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• Allergic rhinitis "Bronchopulmonary aspergillosis"
• Similar to asthma common in CF patients. Can lead to fibrosis of the lungs

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Invasive Aspergillosis

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• Fever, cough, chest pain, facial pain and nasal discharge (sinusitis), headache/eyepain, respiratory distress
• 40% of infected immunocompromised get dissemination to the brain, eye, heart, kidneys, skin

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Aspergillosis can also infect

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Nails

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Mycotoxicosis

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• Produce aflatoxins that cause disease in animals
  
• Found on foods
• A. flavus, A. versicolor, A. nidulans

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Tissue Morphology Hyalohyphomycosis

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• septate hyphae (2-8um)
• Hyphae irregulary arranged
• Branching at 45 and 90 deg
• Phialides and conidia may form in close lesions

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Tissue Morphology Aspergillosis

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• Septate hyphae (3-12um)
• Dichotomous branching at 45 deg angles
• Grow in radial pattern
• Hyphae nearly parallel to one another

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Diagnosis

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• Need to see hyphae in tissue and culture isolation
• Clinical and radiological can add to significance
• Histology: H&E, KOH-Calcofluor white: hyaline septate 3-8um, acute angle branching, not constriction at the septa

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Culture Speciemen

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• Sputum
• BAL
• Lung, sinus, skin, heart
• Blood cultures usually are negative

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Culture Media

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• SAB, BHI, IMA
• Aspergillus differential media: Tyrptone, yeast extract (nutrients), Ferric ions (pigment yellow to olive green)
• Rapid growth in 3 days

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Aspergillus species do not grow on

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• Medium containing cycloheximide

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A. Fumigatus Pathogenicity

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• Frequent agent of sinusitis, non-respiratory infections are infrequent
• Entry is respiratory tract
• The extent of the pulmonary invasion is correlated to immunocomp of the host
• Most common cause of invasive dissem. aspergillosis
• AID cases are secondary; due to steroids and neutropenia
• Rotten material during biological waste treatement

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Aspergillus fumigatus

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• Most common species
• Most common cause of mold infections
• Will grow at 45C (thermophilic)

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Aspergillus fumigatus: Macroscopic

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• Rapidly growing
• Velvety to granular
• Blue-green powdery to slate grey (surrounded by a white bib)
• Reverse cream colored

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Aspergillus fumigatus: Microscopic

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• Smooth conidiophore arises from septae hyphae ending in a round vesicle
• Uniseriate phialides around the top half of the vesicle
• Conidiophores: Colorless to greenish

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Aspergillus flavus

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• Second most common Aspergillus species
• Involves pulmonary, systemic, ear, sinus, and other
• aflatoxin- myotoxin associated with acute liver damage, can lead to liver cancer

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Aspergillus flavus: Macroscopic

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• Rapidly growing
• Cottony to granular
• Yellow green to olive
• Reverse: white to yellow

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Aspergillus flavus: Microscopic

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• Rough conidiophores from septate hyphae ending in a round vesicle
• Produce biseriate or uniseriate phialides around the entire vesicle
• Conidia are round and smooth or finely roughened

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Aspergillus niger

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• Most common in ear infections, frequently in aspergilloma
• Rarely disseminates

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Aspergillus niger: Macroscopic

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• Rapidly growing
• Black and powdery
• Reverse is cream colored

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Aspergillus niger: Microscopic

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• Smooth condiophore from a round vesicle
• Biseriate phialides are produced around the entire vesicle
• Large, hyaline septate hyphae
• Large round black conidia

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Aspergillus Terreus

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• Involves nail, skin, ear, eye, and systemic disease
• Amphotericin B resistant

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Aspergillus terreus: Microscopic

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• Hyaline septate hyphae
• Short conidiophores; compact, columnar conidial heads
• Round hyaline cells produced on mycelium submerged in agar
• Biseriate phialides cover top half of vesicle; round chains of conidia

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Aspergillus ustus

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• Rare human pathogen
• Cutaneous infection in solid organ transplant recipients
• Clinical isolates decrease susceptibility to: anti-fungal drugs: azoles and and echinocadins

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Aspergillus ustus: Macroscopic

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• Potato dextrose agar at 25C: white to yellow to drab gray to brown
• never green
• Yellow diffusing pigment
• Exudate: clear-yellow to purplish brown

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Hulle Cells

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• Large irregular sterile cells bearing small lumen
• Associated with the sexual stage

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Penicillium spp.

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• Don't grow at 37C (except P. marneffei)
• Cycloheximide -
• Macro: growing flat, velvety granular colonies: intially white
• Micro: simple or branched conidiophores
• flask shaped phialides: brush-like clusters
• Conidia are round; unicellular and occur in chains

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Penicillium Morphology Macro

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Macro: green velvet, reverse is cream, may have diffusing pigment

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Penicillium Morphology: Micro

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Micro: conidiophores rise to secondary branches known as metulae. On the tip 3 or more phialides are attached. Phialides produce round conidia

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Gliocladium

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• Contaminant
• Growth within 4 days
• Macroscopy: white with pink or green at center. Fluffy growth. Reverse is white
• Conidia do not form chains instead the conidia CLUMP together forming large balls

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Paecilomyces Clinically Significant species

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• P. variotii- granular velvety colony buff turns tan then yellow brown to olive green; reverse color white to yellow; coniophores 2-7 flask shaped phialides in clusters
• P. lilacinus- granular to velvety; initially white pink to mauve or lilac with white reverse. flask shaped coniophores chains of coniophores at tip of phialides

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Paecilomyces is similar to

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Penicillium spp

Does not grow in the presence of cycloheximide

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Colony Morphology of Paecilomyces

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• Macro: Gold, green-gold, lilac or tan Never blue or green
• Microscopic: phialides swollen at their bases gradually tapering towards their apices; may form a brush-like penicillus
• Tips of phialides are long and tapered
• Conidia are elliptical, vary in size and in the intensity of staining

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Fusarium

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• Infection referred to as: Fusariosis
• Superficial and systemic infections
• Associated with ocular infections
• Disseminated opportunistic infections; particularly in neutropenic and transplant patients
• Use fungal blood cultures

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Fusarium Macroscopic

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• Rapidly growing
• wooly to cottony
• Flat spreading colonies are white to pink to purple; reverse white to pink

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Fusarium Microscopic

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• Phialides on unbranched or branched conidiophores
• Macroconidia 2 or more celled; thickwalled smooth canoe-shaped in bunches
• Microconidia: 1 celled arranged in balls on simple conidiophores

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Annelloconidia

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New conidium is produced by an extension from the previous cell.

The extension retracts leaving a flat, truncated scar, know as an annellide

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Scopulariopsis

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• Associated with nail infections
• Mainly seen in immunocompromised; bone marrow transplant recipients
• Colony morphology: powdery cinnamon brown, gray or cream

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Scopulariopsis: Macroscopic

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Powdery cinnamon brown gray or cream

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Scopulariopsis: Microscopic

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• Chains single celled annelloconidia produced in basipetal succession from an annellide
• Annelides can be solitary, groups, organized into a distinct penicillus
• Conidia are round to light bulb shaped, usually truncate, smooth to rough, and hyaline to brown in color

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Acremonium

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• Mycetoma, corneal and nail infections, rarely become invasive

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Acremonium Macroscopic

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• Surface is compact, folded and felt-like; loose, white, cottony aerial hyphae
• White, gray, or rose in color
• Reverse is colorless to pale yellow or pinkish
• Mature in 5 days

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Acremonium Microscopic

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• Delicate looking
• Fine, narrow hyphae are septate, erect, unbranched
• Tapered phialides form directly on hyphae
• Small, oblong 1 to 2 celled conidia form in clusters at the tips of these phialides
• Slide culture is the best

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Scedosporium boydii-asexual

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• Pseudallescheria boydii (sexual state)
• Cause of mycetoma usually on hands or feet
• Considered an agent of phaeohyphomycosis
• Asexual state can grow on cycloheximide but the sexual state is inhibited