Opportunistic Mycosis
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Opportunistic Fungi
Opportunistic fungi are able to causes disease in immunocompromised patients.
Opportunistic fungi includes: a. Candida albicans. b. Cryptococcus neoformans. c. Aspergillus fumigatus. d. Mucor & Rhizopus species. e. Pneumocystis carinii.
Candida albicans
Characteristics:
● Normal flora of mucous membranes of upper respiratory tract, gastrointestinal tract and genital tract. ● Yeast as normal flora, Pseudohyphae and hyphae when invade tissue.
Candida albicans
Transmission: As part of normal flora, no need of transmission.
Clinical findings:
Thrush: Over growth of C. albicans occurs in the mouth and produces white patches. Common in infants, immunocompromised patients.
Vulvovaginitis: Itching and whitish discharge.
Candida albicans Skin lesion: Warm & moist areas become red and weeping. Fingers and nails of persons employed as dish washers are involved.
Disseminated infection: Such as endocarditis, esophagitis, & endophthalmitis can occur.
Chonic mucocutaneous candidiasis: Occurs in children with T- cell defect immunity.
mucocutaneous candidiasis
Laboratory diagnosis
Sample: According to the site of lesion.
Microscopy: Microscpic examination of tissue reveals yeast and pseudohyphae. The yeast is gram-positive.
Culture: On sabouraud’s agar media colonies are formed. Germ tube formation and production of chlamydospores distinguish C. albicans from other species of Candida.
Laboratory diagnosis
Germ tube test: Inoculate yeast into serum Results in germinated hyphae (within 2 hrs at 37OC for C.albicans) Specific for C.albicans although C.tropicalis sometimes (rarely) produces germ tubes Germ tube test
Candida albicans
Colony on SDA
Candida albicans
Vaginal swab
Mycelium and blastospores in urine
Cryptococcus neofornans
Characteristic:
Oval budding yeast.
Have a wide polysaccharide capsule.
Habitat in the soil containing bird dropping.
Transmission: by inhalation.
Cryptococcus neofornans
Clinical feature: ٭Lung infection is often asymptomatic or may produce flu-like disease or pneumonia. ٭They spread via blood stream to the meninges and other system in patients with reduced cell mediated immunity. ٭But some cases of meningitis may occur.
Laboratory Identification
Microscopy: Visualization of encapsulated yeast in India ink preparation. Gram stain is unreliable but stains such as methenaminesilver, periodic acid-Schiff will allow the organism to be visualized. Culture: On sabouraud’s agar produces colonies of yeast. Serlogy: Capsular polysaccharide antigen can be detected by latex-agglutination test.
Cryptococcus neoformans
Colonies on SDA
Lung section, ecapsulated cells
CSF, India ink, capsule
India ink, phase contrast
Aspergillus
Common species: A. fumigatus, A. flavus, A. niger.
Medical importance: Aspergillus species especially, A. fumigatus cause infections of skin, ears, eyes, “fungus ball” in the lungs.
Aspergillus
Transmission: Inhalation of airborne spores. Clinical feature: Can colonize and invade abraded skin, wound, burn, cornea, ear and paranasal sinuses. In immunocompromised persons invade blood vessels causing thrombosis and infarction. A person with lung cavity e.g; from tuberculosis may develop a fungal ball.
Laboratory Identification
Microscopy: Biopsy specimen shows septate, branching hyphae.
Culture: On sabouraud’s agar produces colonies with characteristic radiating chains of conidia from central stalk.
Colony on SDA
Hyphae in lung section
Aspergillus
Detection of antibody: Patients with allergic bronchopulmonary aspergillosis have high titer of specific IgE antibody.
Detection of antigen: Patients with invasive aspergillosis, their may be high titer of galactomannan antigen.
Pneumocystis carinii
Trophozoite and cyst forms, therefore thought to be a protozoan Responds to protozoan drugs, not to fungal drugs But now classified as a fungus (by rRNA sequencing) Pneumonia-like disease, especially in immunocompromised Common killer in AIDS
Opportunistic fungi are able to causes disease in immunocompromised patients.
Opportunistic fungi includes: a. Candida albicans. b. Cryptococcus neoformans. c. Aspergillus fumigatus. d. Mucor & Rhizopus species. e. Pneumocystis carinii.
Candida albicans
Characteristics:
● Normal flora of mucous membranes of upper respiratory tract, gastrointestinal tract and genital tract. ● Yeast as normal flora, Pseudohyphae and hyphae when invade tissue.
Candida albicans
Transmission: As part of normal flora, no need of transmission.
Clinical findings:
Thrush: Over growth of C. albicans occurs in the mouth and produces white patches. Common in infants, immunocompromised patients.
Vulvovaginitis: Itching and whitish discharge.
Candida albicans Skin lesion: Warm & moist areas become red and weeping. Fingers and nails of persons employed as dish washers are involved.
Disseminated infection: Such as endocarditis, esophagitis, & endophthalmitis can occur.
Chonic mucocutaneous candidiasis: Occurs in children with T- cell defect immunity.
mucocutaneous candidiasis
Laboratory diagnosis
Sample: According to the site of lesion.
Microscopy: Microscpic examination of tissue reveals yeast and pseudohyphae. The yeast is gram-positive.
Culture: On sabouraud’s agar media colonies are formed. Germ tube formation and production of chlamydospores distinguish C. albicans from other species of Candida.
Laboratory diagnosis
Germ tube test: Inoculate yeast into serum Results in germinated hyphae (within 2 hrs at 37OC for C.albicans) Specific for C.albicans although C.tropicalis sometimes (rarely) produces germ tubes Germ tube test
Candida albicans
Colony on SDA
Candida albicans
Vaginal swab
Mycelium and blastospores in urine
Cryptococcus neofornans
Characteristic:
Oval budding yeast.
Have a wide polysaccharide capsule.
Habitat in the soil containing bird dropping.
Transmission: by inhalation.
Cryptococcus neofornans
Clinical feature: ٭Lung infection is often asymptomatic or may produce flu-like disease or pneumonia. ٭They spread via blood stream to the meninges and other system in patients with reduced cell mediated immunity. ٭But some cases of meningitis may occur.
Laboratory Identification
Microscopy: Visualization of encapsulated yeast in India ink preparation. Gram stain is unreliable but stains such as methenaminesilver, periodic acid-Schiff will allow the organism to be visualized. Culture: On sabouraud’s agar produces colonies of yeast. Serlogy: Capsular polysaccharide antigen can be detected by latex-agglutination test.
Cryptococcus neoformans
Colonies on SDA
Lung section, ecapsulated cells
CSF, India ink, capsule
India ink, phase contrast
Aspergillus
Common species: A. fumigatus, A. flavus, A. niger.
Medical importance: Aspergillus species especially, A. fumigatus cause infections of skin, ears, eyes, “fungus ball” in the lungs.
Aspergillus
Transmission: Inhalation of airborne spores. Clinical feature: Can colonize and invade abraded skin, wound, burn, cornea, ear and paranasal sinuses. In immunocompromised persons invade blood vessels causing thrombosis and infarction. A person with lung cavity e.g; from tuberculosis may develop a fungal ball.
Laboratory Identification
Microscopy: Biopsy specimen shows septate, branching hyphae.
Culture: On sabouraud’s agar produces colonies with characteristic radiating chains of conidia from central stalk.
Colony on SDA
Hyphae in lung section
Aspergillus
Detection of antibody: Patients with allergic bronchopulmonary aspergillosis have high titer of specific IgE antibody.
Detection of antigen: Patients with invasive aspergillosis, their may be high titer of galactomannan antigen.
Pneumocystis carinii
Trophozoite and cyst forms, therefore thought to be a protozoan Responds to protozoan drugs, not to fungal drugs But now classified as a fungus (by rRNA sequencing) Pneumonia-like disease, especially in immunocompromised Common killer in AIDS
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