is a pigmented filamentous fungus isolated from soil, rotten wood, and
decomposing plant material. Aside from being a saprophyte, it causes
infections in humans as well. Cold – blooded animals living in swamps may
also be infected. Most cases of infection come from tropical and
subtropical regions. Fonsecaea exhibits in vivo
as it forms sclerotic fission cells only in tissue but grows as a mold in
Fonsecaea only contains two species namely, Fonsecaea compacta
and Fonsecaea pedrosoi.
Pathogenicity and Health Effects
is one of the
causative agents of
chromoblastomycosis which is described as a post – traumatic, chronic
infection of subcutaneous tissues. The infection is characterized by
verrucous cauliflower – like lesions and the formation of brown, sclerotic
fission cells which appear like copper pennies in the tissue.
Most cases of
infection come from tropical and subtropical regions. Fonsecaea
pedrosoi is one of the major causative agents of chromoblastomycosis,
particularly in South
America and Japan. On the other hand, Fonsecaea compacta is a rare
cause of chromoblastomycosis in tropical Central and North America.
Systemic invasion succeeding chromoblastomycosis is very seldom.
species may cause other human infections as well aside from
chromoblastomycosis which include paranasal
fatal brain abscesses following hematogenous dissemination have been
Growth rate is slow and colonies are restricted, flat to raised and folded
with velvety to cottony texture on potato dextrose agar at 25°C;
surface and reverse is brownish black, olive, gray black or jet black in
filamentous appearance is maintained upon cultivation at a temperature of
25, 30, or 37°C.
Hyphae are septate, dark brown and
conidiophores are cylindrical, pale
brown, septate, sub – erect, slightly inflated at the tip, and sympodial
with conidiogenous zones confined at the upper portion;
Blastoconidia are unicellular, ellipsoidal to round in shape and are
formed in ranks successively; and
Conidia are brown and barrel – shaped with size ranging from 1.5 - 3 x 2.5
– 6 µm. There are four types of conidiogenesis that are observed among
type: One – celled conidia arise upon swollen denticles
that are located at the conidiophore tips. These primary conidia become
irregularly swollen at their apices and function as sympodial
conidiogenous cells as well. Then, these conidia give rise to secondary
conidia that are one – celled, pale brown on swollen denticles. Tertiary
series of conidia are often produced by the secondary conidia which are
similar to those formed by the primary conidia, resulting in a complex
conidial head. This type of conidiogenesis does not form long chains of
conidia and is primarily observed among the strains under the genus
type: Vase – shaped conidia with collarettes are located at the
tip of the phialides. This type of conidiogenesis is primarily observed
for the strains of the genus Phialophora and may rarely be observed
in strains of Fonsecaea as well.
type: One – celled, pale brown conidia are formed by the
conidiophores which are sympodial and with denticles. These conidia may
be located at the tips and along the sides of conidiophores. Secondary
conidia are formed rarely. This type of conidiogenesis is primarily
observed for the strains of the genus Rhinocladiella, but
Fonsecaea strains may also exhibit such.
Fonsecaea species must be carefully conducted in a
There are a
limited data available and there is no standard method as yet for in
vitro susceptibility testing of Fonsecaea species. Low MICs
were generated by amphotericin B, ketoconazole, miconazole, itraconazole,
voriconazole, and terbinafine for isolates of Fonsecaea.
Itraconazole and voriconazole appear to have better in vitro
activity than amphotericin B. Also active in vitro against
Fonsecaea pedrosoi is caspofungin. On the other hand, fluconazole has
no practical in vitro activity against Fonsecaea.
Currently used to
treat chromoblastomycosis are cryosurgery and itraconazole. The former is
preferred for small lesions while the latter is applied to larger
lesions. The combination of the two therapeutic modalities may also be
used. In addition, terbinafine also shows promising response in treatment
of chromoblastomycosis. In spite of this, chromoblastomycosis infection
is difficult to treat and most therapeutic approaches provide only a
modest success rate.