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