Mycology Viva With Answer

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Mycology 1. What is is fungus fungus?? What are the proper properties ties of of fungi? fungi? 472/6.5 472/6.5 Fungus: Fungi are eukaryotic, supraphytic parasitic microbes, unicellular or multicelllular that contain chitin in their cell wall and ergosterol and zymosterol in their cell membrane. Fungus: [2] Fungi are chlorophyll free unicellular or multicellular multi cellular eukaryotic organisms reproduce by sexual and asexual sopre formation. Properties of fungi: 1) They They are are non non-m -mot otile ile.. 2) Unice Unicellul llular ar or or multic multicell ellula ular. r. 3) Nucleu Nucleuss are eukary eukaryoti otic. c. 4) Cell Cell wall wall cont contai ains ns chit chitin in.. 5) Cell membrane membrane presents presents Ergostero Ergosteroll and and zymosterol zymosterol.. 6) Cytoplas Cytoplasm m contains contains Mitochond Mitochondria ria & endoplas endoplasmic mic reticulum. reticulum. 7) Sexual Sexual and asexua asexuall spores spores for reproduc reproduction tion not not for survival. survival. 8) Some fungi fungi (Dimorphic (Dimorphic)) shows shows thermal thermal dimorp dimorphism. hism. 9) Most fungi fungi are obligate obligate aerobes aerobes and some are facultative anaerobes, anaerobes, but not strict anaerobes. 10) Some fungi are normal flora. e.g.- Candida albicans 11) Fungi do not have endotoxin endotoxin in their cell wall and do not produce exotoxin. exotoxin. Properties of fungi: (By Dr. Adikary) 1) All fung fungii are euka eukaryo ryotic tic orga organis nism: m: a. Multiple Multiple chromoso chromosome me enclosed enclosed by a membrane, membrane, b. 80S 80S rib ribos osom omee and and c. Mito Mitoch chon ondr dria ia pres presen ent. t. 2) May be Unicell Unicellular ular (Yeast (Yeast)) or Multicel Multicellular lular (Molds) (Molds) 3) Rigid cell cell wall, primari primarily ly made of polysacc polysaccharid haridee (mainly chitin, chitin, glucan glucan)) 4) Cell membrane membrane contains contains ergosterol ergosterol & zymosterol. Some Some fungi fungi possesses possesses capsule. capsule. e.g. C. neoformans. 5) Need Need organi organicc sourc sourcee of carbo carbon. n. 6) Habita Habitat, t, they they have have saprop saprophy hytic tic & paras parasitic itic state state.. 7) Most are obligatory aerobes. Some are are facultative facultative anaerobes. anaerobes. No fungi fungi are strict anaerobe. 8) Can be cult culture ure in in artific artificial ial med media. ia.

2. How fungi fungi diff differ er from from bact bacteri eria? a? 473 473 Difference between fungi and bacteria: Traits Fungus 1. Cellularity Unicellular/ Multicellular 2. Cell wall content Chitin 3. Cell membrane Sterol (Ergosterol & zymosterol) present. 4. Cytoplasm Mitochondria & endoplasmic reticulum present. 5. Nucleus Eukaryotic

Bacteria Unicellular Peptidoglycan Sterol absent (except mycoplasma). Mitochondria & endoplasmic reticulum absent. Prokaryotic

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6. Ribosome 7. Spores

-280S (60S +40S) Sexual and asexual spores for reproduction. Yes (some)

8. Thermal dimorphism 9. Metabolism No obligate anaerobes 10. Motility Non-motile. [Mnemonic: 4C- NuR’S Thermometer May Motile]

70S (50S +30S) Endospores for survival, not for reproduction. No Many obligate anaerobes. Motile/ Non-motile.

3. Why penicillin does not act against fungi? 473 Penicillin does not act against fungi, because — Penicillin acts on peptidoglycan layer of cell membrane, But the fungi do not contain peptidoglycan in their cell membrane, (they contain chitin) that’s why penicillin can not act against fungi. [Need to check]

4. What are the beneficial and harmful effects of fungi? 6.6 Beneficial effect of fungi: 1) In nature, breaking down & recycling of organic matter. 2) Production of food like — bread, cheese, beer, wine etc. 3) Eaten directly as mushroom. 4) Production of antibiotics. (e.g. Penicillin.), Immunosuppressive drugs – (e.g. Cyclosporine.), Anticancer drugs, alkaloids. 5) Production of recombinant vaccine (e.g.  HBsAg vaccine) Harmful effect: 1) As parasites, they can cause disease in plant, animals and human. 2) Food spoilage, toxin production. [Ref: Dr. Adikary]

5. What is dimorphic fungus? Give example. 476 Dimorphic fungus: The fungi able to grow in more than one form under different environmental conditions are known as dimorphic fungi. [Mold= at 22-25 C, Yeast= at 37 C ] Example: — Histoplasma capsulatum • Coccidioides immitis • Paracoccidioides brasiliensis • Blastomyces dermatitidis • [Ref: Dr. Adikary]

6. What is mycoses? Tell morphological classification of fungi. 6.5 , 474 Mycoses: Diseases caused by the fungi are called mycoses. Morphological Classification of fungus: Dermatophytes 1) Molds e.g. — 2) Yeast e.g. — Cryptococcus neoformans 3) Yeast like e.g. — Candida albicans 4) Dimorphic e.g. – Histoplasma capsulatum

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-37. Classify superficial fungi. 475 Superficial fungi are — (and disease produced by them) 1) M alassezia furfur — Tinea versicolor / Pityriasis versicolor 2) E xophiala werneckii — Tinea nigra 3) Piedriaea hortae — Black piedra 4) T richosporon cutaneum — White piedra [Mnemonic: MEPT]

8. How can you diagnose superficial fungal infection in the laboratory? 479 Diagnosis of superficial fungal infection: Specimen: Skin scrapping Microscopic examination: A drop of 20% KOH in scrapping material on a slide ↓ Covered with a cover slip ↓ Slightly heated the slide ↓ Examine under microscope ↓ Observation: • Cluster of yeast cells (grapes-like) • Dense meshwork of short non-septate elongated hyphae. Culture: Usually not needed, But if needed, culture is done in Sabouraud’s dextrose agar (SDA) media at 22 - 25 C for 3 – 4 weeks. Examine the culture media every 3 – 4 days.

9. What is mycoses? Classify mycoses according to sites of involvement. 475 Mycoses: Diseases caused by the fungi are called mycoses. Classification of mycoses according to site of involvement/ Clinical classification: 1) Superficial – Tinea versicolor , Tinea nigra 2) Cutaneous – Dermatophytosis/ Ring worm 3) Sub-cutaneous – Mycetoma, Sporotrichosis, Rhinosporidiosis 4) Systemic/ deep – Coccidioidomycosis, Paracoccidioidomycosis, Histoplasmosis, Blastomycosis, 5) Opportunistic – Systemic candidiasis, Aspergillosis, Mucormycosis [Ref: Dr. Adikary]

10. Define superficial mycoses? Superficial mycoses: Fungal diseases of the superficial layer of epidermis of skin are called superficial mycoses. [need to check]


-411. What is mycetoma? Give pathogenesis. 483/6.20 Mycetoma/ Madura foot/ Maduramycosis: Mycetoma is a chronic granulomatous disease of the subcutaneous and deep tissue. [Agent: fungus: Madurella mycetomatis Bacteria: Actinomycetes(most common)] Pathogenesis:

1. Introduction of the organism by trauma ↓ 2. Formation of nodules at the site of injury ↓ 3. Formation of abscess mainly in subcutaneous tissue but may involve muscle even bone. ↓ 4. Formation of sinuses ↓ 5. Discharge of pus containing coloured granules. [Ref: Dr. Adikary] 12. What is dermatophytoses? Give pathogenesis. 6.17 Dermatophytoses: It is a fungal disease that involves only superficial keratinized structure (skin, hair and nails.) Pathogenesis of Dermatophytoses: Dermatophytes first colonize at certain area of the body. Under suitable conditions, they grow & multiply and produce lesions. • In case of skin, the fungus multiplies & migrates centrifugally, giving an annular appearance of the lesion. The central portion of the lesion gradually heals up & becomes fit for fungus. And the fungus remains in the margin of the lesion. In case of nail, the fungal infection makes the nail soft, brittle, thickened and • ultimately deformed. • In case of hair, the fungal infections break up the hairs and produce a patchy area of alopecia.

13. What is dermatophytoses (ring worm infection)? Name the causative genera.6.17 Dermatophytoses (ring worm infection): It is a fungal disease that involves only superficial keratinized structure (skin, hair and nails.) Causative genera: The most important dermatophytes are classified in three genera: 1. Epidermophyton 2. Trichophyton 3. Microsporum th [Ref: Lange: 11 > 320]


-514. What is ring worm? Why so called? 6.17 Ring worm: A group of fungi which are keratinophilic and have the ability to infect the skin and skin appendages (hair, nail) are called ring worm or dermatophytes. They are called ring worm, because – Lesions produced by them have an inflamed circular border containing papules and vesicles surrounding a clear area of relatively normal skin. th [Lange: 11 > 320]

15. How can you diagnose dermatophytoses of the groin (Tinea cruris) in the laboratory? 482 Diagnosis of dermatophytoses of the groin (Tinea cruris): 1) Specimen: Skin – scrapping 2) Microscopic examination: a. Dissolve the specimen (skin) in 10% KOH for at least 1 hour. b. Findings: Septate hyphae with arthrospore. 3) Isolation & identification from culture: a. Specimen is incubated in Sabouraud’s dextrose agar media at 25 30 C (room temp.) for 3 – 4 weeks. b. Findings: i. Naked eye: 1. Colour: Green, red, white and brown. 2. Texture: Cottony, powdery and velvety appearance. ii. Microscopic examination from colony: 1. Microconidia & macroconidia

16. What is dermatophytoses? Name ring worm infection as per distribution in body sites. Dermatophytoses (ring worm infection): It is a fungal disease that involves only superficial keratinized structure (skin, hair and nails.) Ring worm infection as per distribution in body sites: Ring worm infections Tinea capitis Tinea corporis Tinea cruris Tinea pedis th [Ref: Lange: 11 >320]

Body sites

Head Body Groin Foot

Others: (above 4 +) Tinea unguium: Nails Tinea barbae: Beard. nd [Ref: Lippincott: 2 > 207]


-617. How can you diagnose dermatophytoses of the scalp (Tinea capitis) in the laboratory? Diagnosis of dermatophytoses of the scalp (Tinea capitis): 1) Specimen: Hair – plucking 2) Microscopic examination: a. Dissolve the specimen (hair) in 20% KOH for at least 10 hours. b. Findings: Ectothrix (fungal spores outside the hair shaft) and endothrix (fungal spores inside the hair shaft). 3) Isolation & identification from culture: a. Specimen is incubated in Sabouraud’s dextrose agar media at 25 30 C (room temp.) for 3 – 4 weeks. b. Findings: i. Naked eye: 1. Colour: Green, red, white and brown. 2. Texture: Cottony, powdery and velvety appearance. ii. Microscopic examination from colony: 1. Microconidia & macroconidia

18. Name the genera of fungus causing ring worm infection? Causative genera: The most important dermatophytes (ring worm) are classified in three genera: 1. Epidermophyton 2. Trichophyton 3. Microsporum th [Ref: Lange: 11 > 320]

19. Why KOH is used in the laboratory for diagnosis of ring worm infection directly from clinical specimen? 483 Uses of KOH: KOH is a keratolytic agent which lyses the keratin present in the skin, hair and nail, thus facilitates the separation of fungal elements from skin, hair and nail tissue. In case of ring worm infection (dermatophytoses), the collected specimen contains keratin, so KOH is used in the laboratory for diagnosis of ring worm infection.

20. What is tinea versicolor? Name its causative agent. Tinea versicolor: It is a superficial skin infection of cosmetic importance only. Causative agent: Malassezia furfur th [Ref: Lange: 11 > 321]


-721. How can you diagnose tinea versicolor in the laboratory? 479 Diagnosis of superficial fungal infection/ tinea versicolor/pityriasis versicolor: Specimen: Skin scrapping Microscopic examination: A drop of 20% KOH in scrapping material on a slide ↓ Covered with a cover slip ↓ Slightly heated the slide ↓ Examine under microscope ↓ Observation: • Cluster of yeast cells (grapes-like) • Dense meshwork of short non-septate elongated hyphae. Culture: Usually not needed, but if needed, culture is done in Sabouraud’s dextrose agar (SDA) media at 22 - 25 C for 3 – 4 weeks. Examine the culture media every 3 – 4 days.

22. What is opportunistic mycoses? Name some opportunistic fungi. 489 Opportunistic mycoses: Fungal infection in immunesuppressed person is known as opportunistic mycoses. Some opportunistic fungi are: 1) Candida albicans 2) Rhinosporidium seeberi 3) Pneumocystis carinii 4) Cryptococcus neoformans 5) Mucor [Ref: Dr. Adikary]

23. What are the conditions that favor vaginal candidiasis? Tell laboratory diagnosis of vaginal candidiasis. 491,492 Conditions that favour vaginal candidiasis/ Risk factor for Vaginal candidiasis (monoliasis): 1) Loss of acidic pH of vagina 2) Pregnancy 3) Diabetes mellitus 4) Prolonged use of oral contraceptive pill. 5) Prolonged broad-spectrum antibiotic therapy.


-824. What is oral thrush? How can you diagnose oral thrush in the laboratory? 492, 491 Oral thrush: Oral thrush is the infection of the mucous membrane of mouth and tongue by Candida albicans. Diagnosis of Oral thrush/ Candidiasis: 1) Specimen: Oral swab. 2) Microscopic examination: Wet film preparation with normal saline. 3) Culture a. SDA: shows cream-coloured colonies within 24 to 48 hours. 4) Identification 5) Germ tube test. 6) Biochemical test: Ferments glucose and maltose but not lactose.

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Mycology Viva With Answer

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