Hyaline Hyphomyces Forming Conidia in Clusters

Acremonium

• Often considered a contaminant; may cause mycetoma, corneal infection, onychomycosis, and rarely other disease
• Colonies have a smooth, yeast-like appearance and pastel color or may be felt-like, folded, and compact, evolving to loose, white and cottony. The reverse is colorless, pale yellow, or pink-gray
• Extremely delicate, septate hyphae
• Erect, unbranched, delicate phialides extend at right angles from hyphae
• Conidia are oblong and may resemble clustered grains of rice
• Conidia are easily disrupted; naked phialides and scattered conidia may predominate, as in Figure 2 below

FIG. 1. Acremonium in slide culture. Note the delicate hyphae indicated by the arrowhead and the phialide indicated by the arrow.

FIG. 2. Acremonium. The frail connection between phialide and conidia often makes it difficult to locate clustered conidia at the tip of phialides.

Fusarium

• Generally considered a contaminant, but may cause eye, skin, and systemic infections, usually in immunocompromised people
• Colonies are fast-growing, variable in color and texture, often granular or fluffy, rose-red, purple, or lavender; as with many molds, may start as white, cottony colonies, darkening with maturity. The reverse is pale, but may darken with age
• Septate hyphae
• Two types of sporulation are seen:
  1. large sickle or elliptic macroconidia (11-70 μ length, 3-8 μ width) arise from phialides on branched or unbranched conidiophores
  2. simple conidiophores bearing one- or two-celled microconidia (this pattern can resemble that seen in Acremonium, above)
• Chlamydospores are sometimes present

FIG. 1. Fusarium solani in slide culture. Multicelled macroconidia and chlamydospores dominate this image.

FIG. 2. Fusarium. Macroconidia, septate hyphae, and chlamydospores are present.

Trichoderma

• Usually considered a contaminant; may cause disease in immunocompromised host
• Colonies on Sabouraud. dextrose agar often are white and fluffy when young but are typically green, granular, and poorly demarcated with maturity, growing across the entire plate; this has been termed the "green lawn" appearance (see also Gliocladium, below)
• Phialides resemble those of Paecilomyces (bowling pin form) and extend in pairs opposite of one another at 45° from the hyphae
• Conidia appear singly or in clusters at the tip of the phialides in a somewhat less organized pattern than Gliocladium, and are 3μ in diameter

FIG. 1. Trichoderma in slide culture.

Gliocladium

• Usually considered a contaminant
• Colonies on Sabouraud. dextrose agar are white initially, but typically become green, granular, poorly demarcated, and grow across the entire plate, resembling a "green lawn" (see also Trichoderma, above)
• Phialides branching and tapered at tips
• Spherical conidia are gathered at tip of phialides in a tight, ball-shaped cluster and are often somewhat larger than those of Trichoderma

FIG. 1. Gliocladium in slide culture.

To examine other groups of hyalohyphomyces, follow the links below:

• Aspergillus
• Link for hyalohyphomyces bearing conidia in chains
• Hyalohyphomyces bearing conidia singly