Cladosporium Species

ENVIRONMENTAL

Cladosporium spp. are primarily recovered as environmental contaminants. Ubiquitous in nature, this isolate can be recovered from almost any location in the world. Cladosporium spp. form brown to olive to black hyphae and conidia. Conidiophores are erect and can branch into several conidiogenous cells. Spherical to ovoid conidia form blastically on the end of each previously formed conidium. Branched conidium-bearing cells may dislodge, and the three scars on each of these cells give them the appearance of a shield. Generally, conidial chains of the saprophytic species break up easily, whereas those of pathogenic species remain connected. These organisms are slowly to moderately growing phaeoid fungi, with granular velvety to fluffy colonies, ranging in color from olive to brown or black.

SEPTATE OPPORTUNISTS

Hyphae of most opportunists molds contain cross-walls. Those of medical importance fall into the phylum Deuteromycota. The septate opportunistic molds may be divided into those that are dematiaceous (dark-colored hyphae and/or conidia), and those that are hyaline (light colored hyphae and conidia). Organisms with dark hyphae on tease mounts also have dark green to black colonies, especially on the colony reverse. The colonial color aids in the initial identification. Hyaline organisms exhibit light-colored colonial aerial hyphae, but they may be covered over with brightly colored comidia; thus, a tease mount is required. In the following descriptions, key identifying features are capitalized.

DEMATIACEOUS OPPORTUNISTS

Opportunists with dark-colored hyphae may cause phaeohyphomycosis (infection caused by dematiaceous fungi).

PATHOGENICITY

In tropical areas, agents such of Cladosporium spp. can cause chromoblastomycosis, characterized as verrucous nodules that often become ulcerated and crusted. This disease is diagnosed by the presence of characteristic lesions accompanied by microscopic sclerotic bodies, often referred to as copper pennies because of their shape and staining properties in tissue sections. Cladosporium spp. could potentially cause keratomycosis and allergic responses. Infections are typically confined to the sinuses or following traumatic inoculation.

LABORATORY EVALUATION

CULTURE

On SABHI agar at room temperature, the colony is moderately slow-growing for an opportunist, requiring 7 days. It is powdery or velvety, heaped and folded, and dark gray-green with the reverse black.

MICROSCOPIC

The septate hyphae are DARK-colored. Short CHAINS of dark one- to four- celled BLASTOCONDIDIA with a distinct SCAR at each point of attachment are borned from REPEATEDLY FORKING SHIELD CELLS (shield-shaped conidiogeneous cells).