is a cosmopolitan filamentous fungus commonly isolated from soils and from
numerous mammalian species, such as small rodents. It has the ability to
produce a distinctive structure known as
adiaspore at 37 – 40oC
thus, considered as a dimorphic fungus as well. Emmonsia species
is an occasional causative agent of animal and human infections.
Emmonsia parva is known to be prevalent in
Southwestern USA, and Eastern Europe while Emmonsia crescens has
been reported worldwide.
genus Emmonsia currently consists of four species, namely:
Emmonsia parva, Emmonsia parva var. crescens,
Emmonsia parva var. parva, and Emmonsia pasteuriana.
Emmonsia parva is occasionally referred to as Chrysosporium parvum.
Pathogenicity and Health Effects
species is the etiologic agent of
animals and more rarely in humans and is described as asymptomatic
pulmonary infection which may disseminate in immunocompromised patients,
such as those with AIDS. The said infection develops after breathing in
of Emmonsia conidia. Then, these
conidia, which are also called
as adiaspores, enlarge in the alveoli and hinder regular pulmonary
functions. Additionally, adiaspores only remain at their primary
implantation site and do not reproduce and eventually, become calcified
and lead to a minimal reaction in the host tissue. Emmonsia parva
var. crescens is the primary species isolated from humans while
Emmonsia parva var. parva is mostly isolated from animals.
Additionally, Emmonsia pasteuriana has recently been isolated from
a cutaneous disseminated infection in an HIV – infected patient.
Growth rate is moderately rapid and colonies have glabrous to velvety
Surface colony color is white and may have buff to pale brown center and
while cream to pale brown on the reverse.
Hyaline septate hyphae,
conidiophores, and aleuriconidia are present while
adiaspores are only formed at 37 – 40oC in vivo or on
blood or brain heart infusion agar in vitro;
Conidiophores are simple or sometimes branching at right angles;
Aleuriconidia are hyaline, unicellular, round in shape and lightly
roughened, sessile or located on slender stalks, usually solitary or may
form two to three – celled chains, and 2 - 5 x 2 - 4 µm in size;
conidia tend to swell and give rise to adiaspores which are thick -
walled, big conidia liberated at 37 - 40°C;
only Emmonsia species which do not produce adiaspores is
Emmonsia pasteuriana which only produces budding cell – like cells
structures at 37oC on brain – heart infusion agar;
Adiaspores of the two varieties of Emmonsia parva may differ in
size, structure and in their required temperature for their optimum
growth; For Emmonsia parva var. parva, adiaspores are
uninucleate, may reach 25 µm in vitro and 40 µm in vivo and
are formed at 40oC while the adiaspores of Emmonsia parva
var. crescens are multinucleate, may be bigger compared to those of
Emmonsia parva var. parva and are formed at 37oC.
Only general laboratory precautions are required, no special safety