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Fungi Causing Systemic Mycoses
= majority causes inapparent infection = causative organism are dimorphic fungi
1. Blastomyces dermatitides
Characteristics: = dimorphic can exist as:
mold in soil, yeast in tissueYeast form is round-shaped with a
thick refractile wall and single
broad-based bud = natural habitat Is soil rich in organic
material
Disease: Blastomycosis (Gilchrist’s Dse, North American) Blastomycosis
= a chronic infection characterized by formation of
suppurative and granulomatous lesion found
mainly in the lungs and disseminate
throughout the body
MOT = inhalation of airborne spore (conidia)
Pathogenesis: = infection occurs mainly in the respiratory tract
= inhaled conidia differentiate into yeast
cell which initially cause abscesses
followed by formation of granuloma
= dissemination rare, but when it occurs
skin and bone are the most commonly involved.
Laboratory Diagnosis:1. Direct microscopic examination of sputum or skin scrapping (KOH mount)/Tissue biopsy:
= demonstrate charac. thick walled “yeast cell with
single broad-based bud”2. Culture - SDA
= grows as fluffy, brownish to white fungus which
produces pyriform spores 3. Hypersensitivity test – Blastomycin test = Serological test not useful
Treatment: Itraconazole (drug of choice)Amphotericin B - used to treat severe
cases Surgical excision helpful
Prevention: No vaccine or prophylactic drug available
2. Coccidiodes immitis Characteristics:
= dimorphic fungus that exist as: spherules in tissues containing
endospores mold at 250C in soil which
forms hyphae withalternating arthrospores
= natural habitat is soil
Disease: Coccidiodomycosis (San Joaquin Valley Fever,)
Dessert Fever= disease simulate pneumonia wherein large part of the lung becomes consolidated
MOT: inhalation of airborne arthrospores
Pathogenesis: Arthrospores inhaled to the lungs
forms spherules filled with endospore rupture endospore release forms new spherules
disseminate throughout the body
Septate hyphae
Arthroconidia
Septate hyphae
Laboratory Diagnosis:A) Microscopic examination of tissue scrapping or sputum
(KOH mount) = demonstrate the characteristic
spherules containing endospores
B) Culture Sabouraud medium – presence of hyphae containing
arthrospores. C) Serological test Precipitin test– demonstrate a rising titer of IgM Ab
(indicates recent infection) CF test - a rising titer IgG antibody indicates
dissemination of infection D) Skin test – Coccidioidin test – using mycelial extract or
spherulin (an extract from spherules) as
antigen = (+) test indicate prior infection but not
necessarily active disease
= useful in determining whether patient has been
infected
Treatment: Ketoconazole (for primary infection) Amphotericin B/Itraconazole (for disseminated infection) Fluconazole - drug of choice in cases of meningitis
Prevention: No vaccine and Prophylactic drug available
3. Paracoccidiodes braziliensis Characteristics:
= dimorphic fungus exist as: mold in soil yeast in tissue
(yeast form is thick walled with multiple buds) resembling a ship steering-wheel
= habitat - soil Disease: Paracoccidioidomycosis
(South American Blastomycosis)= chronic granulomatous disease of the
skin,mucous membrane, lymph node and internal organs.
MOT : inhalation of airborne conidia
Pathogenesis: = spores are inhaled an early lesion occurs
ion the lungs which disseminate to other organ
= asymptomatic infection common
Laboratory Diagnosis:A) Direct microscopic examination from
pus or tissues (KOH mount)= presence of large yeast cell
w/multiple buds
B) Culture Sabourauds agar – presence of septate
hyphae with microconidia
C) Skin test not useful D) Serological: CF/Immunodiffusion test - rise
in AB titer significant
Treatment: Itraconazole
Prevention: No vaccine available, Prophylactic drug available
4) Histoplasma capsulatum
= dimorphic fungus that exist as:yeast cell in tissue w/c forms 2types of asexual
sporea) Tuberculate macroconidia
(thick-walled finger like projection)b) Microconidia- thin, small, smooth-
walled mold in soil enriched with bird droppings
Disease: Histoplasmosis (Darling’s Disease) = acute, benign pulmonary disease acquired by
inhalation of airborne spores (microconidia)
which are present from dropping of birds = inhaled spore are engulfed by
macrophages which developed in to yeast form
= in tissue the organism occurs as oval body yeast
cell inside macrophages which spread
throughout the body especially liver and spleen
Laboratory Diagnosis: A. Microscopic examination of sputum, tissue biopsy, bone
marrow aspirate = oval yeast cell within macrophages
B. Culture Sabourauds agar = presence of septate hyphae
with tuberculate chlamydospore in culture at
250C is diagnostic
BHIA – presence of fusiform blastospores with large
vacuole giving a characteristic cresent-shaped
appearance C. Skin test – Histoplasmin test
-using mycelial extract as antigen -useful for epidemiologic determination of incidence of infection -not use to diagnose actual disease
Treatment: Amphotericin B – for disseminated infection
Itraconazole - for pulmonary infectionPrevention: None (no vaccine available)
Budding yeast cell inside macrophages
Fungi Causing Opportunistic Mycoses
= produce disease in those individual with impaired host
defenses
1. Candida albicans
Characteristics: = is an oval yeast cell with a single bud = part of the normal flora of the mucous
membrane of the upper respiratory tract,
gastrointestinal and female genital tract
= in tissues can appear as yeast cell or as psuedohyphae (which are elongated yeast
that visually resembles hyphae but are not true
hyphae)= CHO fermentation reaction differentiate C-
albicans from other specie of Candida
MOT: - part of the normal of the skin, mucous membrane and gastrointestinal tract of human
= no person to person transmission
Pathogenesis: Opportunistic pathogen= disease may results when host defenses
are impaired
Diseases: 1. Thrush (Moniliasis)2. Vulvovaginitis 3. Infection of the Nail (Paronychia)4. Skin lesion occurs frequently in moisture-
damage skin 5. Systemic Candidiasis (disseminated
form)
Laboratory Diagnosis:A. Direct microscopic examination (KOH mount) = presence of budding yeast cell w/pseudohyphae B. Culture
SDA – presence of yeast cell, pseudohyphae
and large chlamydospore
Germ tube form in serum at 370C differentiate albicans from other species
C. Skin test with candida antigen = (+) among immunocompetent
adult and are used as indicator that a
person can mount a cellular immune response
Treatment: Nystatin / Miconazole oral/topical for skin and mucous membrane disease Amphotericin B - disseminated infection
Ketoconazole – for chronic mucocutaneous candidiasis
Prevention: No vaccine available = predisposing factors should be reduced or
eliminated = Clotrimazole trochis / Nystatin–used for
prevention of oral thrush
2. Aspergillus fumigatus/Aspergillus flavus/Aspergillus niger
Characteristics: = exist only as mold with septate hyphae that
branch at a V-shaped angle
= monomorphic = organism is normally found in soil
Diseases: 1. Aspergillosis (major disease) = a granulomatous necrotizing disease of the
lung which often disseminates hematogenously to
various organs of the body= involving the skin, eyes, ear, and other vital
organ= acquired by inhalation by airborne conidia = can colonize and invade abraded skin and
paranasal sinuses causing fungal sinusitis
2. Allergic bronchopulmonary aspergillosis
3. Aspergilloma (fungus ball in the lung)
Pathogenesis: = opportunistic pathogen = produce invasive disease among
immunocompromised individual
= organism can invade bloodvessels causing thrombosis and infarction
= patient with lung cavity (tuberculosis) may develop
fungal ball (Aspergilloma)= allergic patient with bronchial asthma can
develop allergic bronhopulmonary aspergillosis
Laboratory Diagnosis:A. Microscopic examination (KOH mount) =
presence of hyaline septate hyphae, dichotomously
branched B. Culture – SDA – shows colonies with
characteristic radiating chain of conidia
C. Serological – detect IgG precipitin in patient with aspergilloma and IgE antibody in patient with bronchopulmonary aspergillosis
D. Skin test – not available
Treatment: Amphotericin B – for invasive aspergillosis Surgical removal – for aspergilloma
(fungus ball)Steroid – recommended for allergic
bronchopulmonary aspergillosis
Prevention: No vaccine / Prophylactic drug available
3. Rhizopus/Mucor
Characteristic: = mold with non-septate hyphae w/
sporangiospore that typically branch at 90O angle
= monomorphic = habitat in soil
MOT: inhalation of airborne spores
Disease: Mucormycoses (Zygomycoses; Phycomycoses)
= is a systemic disease cause by saprophytic mold
(Mucor, Rhizopus and Absidia) found widely
in the environment = acquired by inhalation of airborne asexual
spore
Laboratory Diagnosis:1. Microscopic examination of tissue (KOH mount)
= presence of non-septate hyphae that branch at
wide right angle 2. Culture – SDA - large hyaline coenocytic hyphae with spores found inside sporangium
3. Serologic test – not available
Treatment: Amphotericin B
Prevention: No vaccine / Prophylaxis drug available
4. Cryptococcus neoformans= is an oval yeast-like budding cell
surrounded by a wide polysaccharide capsule
= not dimorphic= habitat soil enriched with pigeon
droppings Disease: Cryptococcosis(Torulosis, European Blastomycosis)
= most common life-threatening fungal disease in
AIDS patient MOT: inhalation of airborne yeast cell
= no human to human transmission Pathogenesis:
= lung infection as a result of inhalation is often
asymptomatic or may produce pneumonia
= disease occurs in patient with altered cell mediated immunity especially AIDS
patient = spread via blood stream to the
CNS and result to Cryptococcal Meningitis
Laboratory Diagnosis:= Direct visualization of the encapsulated yeast-like
budding cell from spinal fluid by India Ink staining
(yeast cell surrounded by a wide unstained capsule) = Culture (spinal fluid/sputum) SDA – presence of
encapsulated yeast cell. = Serological – Latex particle agglutination test
- detects polysaccharide capsular antigen in
spinal fluid
Treatment: Amphotericin B plus Flucytosine for meningitis
Prevention: No vaccine = Cryptococcal meningitis can be prevented
in AIDS patient by oral Fluconazole
Capsule
Budding yeast
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