bertholletiae showing simple sporangiophores
forming a swollen, terminal vesicle around which single-celled,
globose to ovoid sporangiola develop on swollen denticles.
Colonies on Sabouraud's agar are very fast growing, white at
first, but becoming rather dark grey and powdery with
development. Sporangiophores to 20 um wide, straight, with
verticillate or solitary branches. Vesicles subglobose to
pyriform with the terminal ones up to 40 um and the lateral ones
10 to 30 um in diameter. Sporangiola are globose (7-11 um
diameter), ellipsoidal (9-13 x 6-10 um), verrucose or short-echinulate,
hyaline singly but brownish in mass. Temperature: optimum
25-30C; maximum up to 50C.
genus Cunninghamella is characterized by white to grey,
rapidly growing colonies, producing erect, straight, branching
sporangiophores. These sporangiophores end in globose or
pyriform-shaped vesicles from which several one-celled, globose
to ovoid, echinulate or smooth-walled develop on swollen
denticles. Chlamydoconidia and zygospores may also be present. Cunninghamella
species are mainly soil fungi of the Mediterranean and
subtropical zones, and they are only rarely isolated in
temperate regions. The genus now contains seven species, with C.
bertholletiae the only species known to cause disease in man
is a filamentous fungus found in soil and plant material, particularly at
Mediterranean and subtropical zones. It has also been recovered from
animal material, cheese, and Brazil nuts. In addition to being a common
contaminant, Cunninghamella is an opportunistic fungus that may
cause infections in immunocompromised hosts.
The genus Cunninghamella
currently contains seven species. While Cunninghamella bertholletiae,
Cunninghamella elegans, and Cunninghamella echinulata are
the most common species, Cunninghamella bertholletiae is the only
known human and animal pathogen. The nomenclature for Cunninghamella
species is rather complicated. While some authorities accept Cunninghamella
bertholletiae, Cunninghamella elegans, and Cunninghamella
echinulata as separate species, others tend to use the names Cunninghamella
bertholletiae and Cunninghamella echinulata as the synonyms of Cunninghamella
elegans. However, the latter approach is not very convincing, since
the purely gray color of its colonies and its inability to grow at 45°C
clearly differentiates Cunninghamella elegans from Cunninghamella
bertholletiae. Thus, we prefer to follow the previous approach and
accept the existence of the three species separately in the genus Cunninghamella.
Pathogenicity and Clinical
spp. are among the causative agents of zygomycosis. Although
the term mucormycosis has often been used for this syndrome, zygomycosis
is now the preferred term for this angio-invasive disease. Trauma,
diabetes mellitus, immunosuppression due to various reasons (hematological
malignancies, organ transplantation, AIDS), and desferoxamine therapy are
the major risk factors for development of zygomycosis. Among the other
genera belonging to the class zygomycetes, Cunninghamella is
particularly sensitive to desferoxamine therapy. Lastly and importantly, Cunninghamella
infections have been reported in a number of cases receiving antifungal
prophylaxis with itraconazole.
bertholletiae may cause rhinocerebral, pulmonary, cutaneoarticular,
and disseminated forms of zygomycosis. The infection usually starts after
inhalation of the spores or inoculation of the fungus following the
primary breakdown of the skin integrity due to a trauma.
colonies are rapidly growing (mature in 4 days), cottony, and white to
tannish-gray in color. The reverse is pale. Cunninghamella elegans
produces purely gray colonies. While Cunninghamella bertholletiae
may grow at temperatures as high as 45°C, Cunninghamella elegans
fails to grow at this temperature.
or sparsely septate broad hyphae, sporangiophores, terminal vesicles,
sporangioles (sporangiola; sing. sporangiolum), and sporangiospores are
visualized. Sporangiophores are erect and form short lateral branches each
of which terminates in a swollen vesicle. The vesicle (30-65 µm in
diameter) has spine-like denticles on its surface. Sporangioles (5-8 x
6-14 µm) are round to oval in shape, one-spored, and are formed on these
denticles. Sporangiospores are one-celled, solitary, and globose to ovoid
in shape. The walls of the spores often have needle-like crystals.
Zygospores have tuberculate projections and may form only after
appropriate mating studies.
precautions other than general laboratory precautions are required.
Very few data
are available and there is as yet no standard method for in vitro
susceptibility testing of Cunninghamella species. In an in vitro
study where two Cunninghamella echinulata strains were tested, the
rank of MICs was found to be voriconazole, ketoconazole, amphotericin
B, itraconazole. On the other hand, amphotericin B,
ketoconazole, and itraconazole generated considerably high MICs for some
isolates of Cunninghamella spp. in other workers' hands. Liposomal
amphotericin B has been used for treatment of Cunninghamella
infections. However, prognosis is often poor.