Systemic mycoses
Systemic mycoses
H. capsulatum
is a dimorphic fungus that exists
as a mold in soil and as a yeast in tissue. • It
forms two types of asexual spores (1)
tuberculate macroconidia, with typical thick
walls and finger like projections that are
important in laboratory identification, (2)
microconidia, which are smaller, thin, smooth
walled spores that, if inhaled, transmit the
infection.
Transmission & Epidemiology of
Histoplasma
In areas of endemic infection, excavation of the
soil during construction or exploration of bat
infested caves has resulted in a significant
number of infected individuals. • In several
tropical African countries, histoplasmosis is
caused by
Histoplasrna duboisii
. • The clinical
picture is different from that caused by
H.
capsulatum
ECOLOGICAL ASSOCIATION
•
Blackbird roosts • Bats • Bat guano • Chicken houses
•
Pathogenesis & Clinical Findings of Histoplasma
•
Inhaled spores are engulfed by macrophages and
develop into yeast forms. • In tissues,
H. Capsulatum
occurs as an oval budding yeast inside
macrophages.The yeasts survive within the
phagolysosome of the macrophage by producing
alkaline substances, such as bicarbonate and
ammonia, that raise the pH and thereby inactivate
the degradative enzymes of the phagolysosome • The
organisms spread widely throughout the body;
especially to the liver and spleen, but most infections
remain asymptomaric, and the small grantdomatous
foci heal by calcification.
Blastomycosis
Is similar to histoplasmosis, is a primary pulmonary
infection resulting from inhalation of conidia from
the mycelial phase of
Blastomyces dermatitidis
which convert in vivo to the parasitic yeast phase.
Blastomycosis (due to
B dermatitidis
) in the
blastoconidial phase also causes a primary
pulmonary infection. The organism elicits a
granulomatous reaction often associated with a
marked fibrotic reaction. The clinical pattern of
pulmonary blastomycosis is one of chronic
pneumonia. Dissemination occurs most commonly
to the skin, bone, and, in males, prostate.
Cryptococcus neoformans
Although the genus
Cryptococcus
contains more than 50
species, only
C neoformans
and
Cryptococcus gattii
are
considered principal pathogens in humans. Previously,
C
neoformans
was defined as having two varieties—
var
neoformans
and var
gattii
. However, based on the
elucidation of the genomic sequences,
C
neoformans
and
C gattii
are now considered two distinct
species.
C neoformans
is the most common species in the
United States and other temperate climates throughout
the world and is found in aged pigeon droppings. Until
recently,
C gattii
was found principally in tropical and
subtropical climates.
C gattii
is not associated with birds
but grows in the litter around certain species of
eucalyptus trees.
Worldwide,
C neoformans
serotype A causes most
cryptococcal infections in immunocompromised
patients, including patients infected with HIV. For
unknown reasons,
C.gattii
rarely infects persons with
HIV infection and other immunosuppressed patients.
Patients infected with
C gattii
are usually
immunocompetent, respond slowly to treatment, and
are at risk for developing intracerebral mass lesions
(eg, cryptococcomas).
C neoformans
reproduces by
budding and forms round yeastlike cells that are 3-6
µm in diameter. Within the host and in certain culture
media, a large polysaccharide capsule surrounds each
cell.
C neoformans
forms smooth,
Systemic mycoses are fungal infections caused by dimorphic fungi such as Histoplasma capsulatum, Blastomyces dermatitidis, and Cryptococcus neoformans. Histoplasmosis is transmitted through inhalation of spores from soil or bat-infested caves, presenting with tuberculate macroconidia and microconidia. Blastomycosis results from inhaling conidia, leading to pulmonary infection and potential dissemination to skin, bone, and prostate. Cryptococcus neoformans is commonly found in aged pigeon droppings and C. gattii in the litter around eucalyptus trees, with both species considered principal pathogens in humans.
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Presentation Transcript
Systemic mycoses H. capsulatum is a dimorphic fungus that exists as a mold in soil and as a yeast in tissue. It forms two types of asexual spores (1) tuberculate macroconidia, with typical thick walls and finger like projections that are important in laboratory identification, (2) microconidia, which are smaller, thin, smooth walled spores that, if inhaled, transmit the infection.
Transmission & Epidemiology of Histoplasma In areas of endemic infection, excavation of the soil during construction or exploration of bat infested caves has resulted in a significant number of infected individuals. In several tropical African countries, histoplasmosis is caused by Histoplasrna duboisii. The clinical picture is different from that caused by H. capsulatum
ECOLOGICAL ASSOCIATION Blackbird roosts Bats Bat guano Chicken houses Pathogenesis & Clinical Findings of Histoplasma Inhaled spores are engulfed by macrophages and develop into yeast forms. In tissues, H. Capsulatum occurs as an oval budding yeast inside macrophages.The yeasts survive within the phagolysosome of the macrophage by producing alkaline substances, such as bicarbonate and ammonia, that raise the pH and thereby inactivate the degradative enzymes of the phagolysosome The organisms spread widely throughout the body; especially to the liver and spleen, but most infections remain asymptomaric, and the small grantdomatous foci heal by calcification.
Blastomycosis Is similar to histoplasmosis, is a primary pulmonary infection resulting from inhalation of conidia from the mycelial phase of Blastomyces dermatitidis which convert in vivo to the parasitic yeast phase. Blastomycosis (due to B dermatitidis) in the blastoconidial phase also causes a primary pulmonary infection. The organism elicits a granulomatous reaction often associated with a marked fibrotic reaction. The clinical pattern of pulmonary blastomycosis is one of chronic pneumonia. Dissemination occurs most commonly to the skin, bone, and, in males, prostate.
Cryptococcus neoformans Although the genus Cryptococcus contains more than 50 species, only C neoformans and Cryptococcus gattii are considered principal pathogens in humans. Previously, C neoformans was defined as having two varieties var neoformans and var gattii. However, based on the elucidation of the genomic sequences, C neoformans and C gattii are now considered two distinct species. C neoformans is the most common species in the United States and other temperate climates throughout the world and is found in aged pigeon droppings. Until recently, C gattii was found principally in tropical and subtropical climates. C gattii is not associated with birds but grows in the litter around certain species of eucalyptus trees.
Worldwide, C neoformans serotype A causes most cryptococcal infections in immunocompromised patients, including patients infected with HIV. For unknown reasons, C.gattii rarely infects persons with HIV infection and other immunosuppressed patients. Patients infected with C gattii are usually immunocompetent, respond slowly to treatment, and are at risk for developing intracerebral mass lesions (eg, cryptococcomas). C neoformans reproduces by budding and forms round yeastlike cells that are 3-6 m in diameter. Within the host and in certain culture media, a large polysaccharide capsule surrounds each cell. C neoformans forms smooth,
