Endemic mycoses (systemic)
Fungal infection caused by agents that are highly virulent, can invade deeply into tissues
and organs.
The main disease and their etiological agents are:
Histoplasmosis Histoplasm capsulatum.
Blastomycosis Blastomyces dermatiditis.
Coccidioidomycosis Coccidioides immitis.
Paracoccidioidomycosis Paracoccidioides brasiliensis
Histoplasma capsulatum
1. Is a dimorphic, soil saprophytics fungus.
mycelial form present in the soil and yeast
form after inhlation within the cell of RES
2. The mycosis (disease) caused by H. capsulatum known as histoplasmosis, which is an
intracellular, within RES , not contagious, and man is infected by inhalation of spores.
Severity of the disease related to the intensity of exposure .
3. Histoplasmosis is the most prevalent pulmonary mycotic infection in humans.
Pathogenesis : histoplasmosis
1) After inhalation, the conidia (spores) develop into yeast cells and are engulfed by
alveolar macrophages,
2) they are able to replicate. Within macrophages,
3) the yeasts may disseminate to reticuloendothelial tissues such as liver, spleen, bone
marrow, and lymph nodes.
4) The initial inflammatory reaction becomes granulomatous.
Clinical types :
symptomatic
infection :
1. which is
present in
about 95% of
the exposed
patients.
2. The
cell-mediated
immune
inhibit
intracellular
growth of the
yeasts.
Acute pulmonary
1. This type is a
self-limited
flu-like
syndrome,
with fever,
chills,
myalgias, and
nonproductiv
e cough.
2. These
symptoms
resolve
spontaneousl
y without
therapy .
Chronic
pulmonary is
usually a
reactivation
process, breakin
down of a
dormant lesion .
Severe
disseminated
histoplasmosis
The
reticuloendotheli
al system mainly
involved
1. enlarged
spleen and
liver, high
fever, anemia,
2. high mortality
rate if no
antifungal
therapy
used.
Primary
cutaneous these
are mostly
laboratory
acquired
infection.Local,
self limiting
ulcers develop.
Laboratory diagnosis
Direct examination
Culture
A. The media used are: B.H.I. agar with
blood, Yeast extract phosphate agar,
Sabouraud's agar
B. For the conversion of mold to yeast form,
Blood glucose cysteine (BGC) agar or BHI
agar with blood
Exoantigen test or nucleic acid probe test
serodiagnosis, the two tests that are widely
available, the immunodiffusion assay and
complement fxation test.
Microscopically the diagnostic form apear
after colony is mature and it is large, rough
walled with finger like projections
Treatment
Amphotricin B.
Ketoconazole or itraconzole.
Blastomyces dermatitidis
A. Is a dimorphic fungus.
B. Blastomyces dermatitidis cause
blastomycosis, a chronic infection with
granulomatous
and suppurative lesions that is initiated in the lungs.
Pathogenesis
1. Infection occurs by inhaling the conidia of the fungus into the alveoli, then transform at
body temp. to the yeast phase, and reproduce by budding.
2. This transformation provides a survival advantage provides resistance to phagocytosis
and induce expression of an immune-modulating virulence factor (BAD-I) on the cell
surface.
3. The evoked pyogranulomatous inflammatory response has an initial influx of
neutrophils, followed by macrophage and granuloma formation.
Clinical findings
Pulmonary: About 50% of
patients are asymptomatic
in other sympotom are fever
and cough with pulmanary
infltrate that is diagnosid as
atypical pneumonia .
Subacute to chronic
pulmonary form: The
common symptoms of this
form are fever, cough, chest
pain.
The lesions may be cavitary,
nodular, fibrotic or mass like
in appearance.
Extrapulmonary:
dissemination occur in
patients with chronic illness
and in those who are
immunocompromised.
When dissemination occurs,
skin lesions are most
common
Reactivation of the disease
occur after pulmonary
infection.
Diagnostic laboratory tests
1. Specimen : sputum, pus, urine, and
biopsies from lesions.
2. Microscopic appearance: broadly
attached bud on thick yeast cell
3. Culture: on sabouraud's agar ,, The
identification is confirmed by conversion
of the mold form to yeast after cultivation
on enriched media
4. Serology: serologic tests are not useful
for the diagnosis of blastomycosis as
other endemic mycosis
Treatment
A. Amphotericin B.
B. Itraconazole is effective.