1 / 33

Mycology – Yeast

Mycology – Yeast. Student Lab Division of Medical Technology Carol Larson MSEd, MT(ASCP). Basic Characteristics. Unicellular Generally normal flora. Basic Characteristics. Asexual reproduction Blastoconidia Pseudohyphae Arthroconidia. Direct Examination.

amaranta-nova
Download Presentation

Mycology – Yeast

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mycology –Yeast Student Lab Division of Medical Technology Carol Larson MSEd, MT(ASCP)

  2. Basic Characteristics • Unicellular • Generally normal flora

  3. Basic Characteristics • Asexual reproduction • Blastoconidia • Pseudohyphae • Arthroconidia

  4. Direct Examination • Observe for reproductive structures • Gram stain • Gram positive • India ink stain • Capsules

  5. Growth Requirements • Growth in 2-3 days • Temperature • 25-37ºC • Best at 30ºC

  6. Colony Morphology • Appearance • Similar to bacteria colony • Texture • Glabrous • May be filamentous • Pigmentation • Confuse with Staphylococcus

  7. Yeast ID Methods • Germ Tube Production • First test performed when yeast • Procedure • Interpretation

  8. Yeast ID Methods • Cornmeal-Tween 80 agar • Procedure • Observe microscopically for • Chlamydospores • Blastoconidia • Pseudohyphae • Arthrospores

  9. Yeast ID Methods • Niger Seed Agar (Birdseed agar) • Procedure • Observe for brown pigment caused by phenol oxidase activity • Cryptococcus neoformans

  10. Yeast ID Methods • Urease • Procedure • Positive: • Cryptococcus sp. (rapid) • Trichosporon sp. • Rhodotorula sp. • Negative: • Candida sp. • Geotrichum sp.

  11. Yeast ID Methods • Carbohydrate assimilation • Utilize carbohydrate as sole source of carbon in the presence of oxygen • Positive = growth • Carbohydrate fermentation • Utilize a carbohydrate anaerobically • Positive = gas

  12. Yeast ID Methods • Commercial identification kits • Manual methods • Automated methods

  13. Candida species • Normal flora • Leading opportunistic fungal infection in man • Candidiasis • Mucocutaneous • Cutaneous • Systemic

  14. Factors predisposing to infection • Immunocompromised • Malignancy • Prolonged antibiotic therapy • Lupus, Diabetes • Pregnancy and use of birth control pills • Age • Damaged skin barrier

  15. Candida albicans • #1 fungal isolate in laboratory • Germ tube: positive • CMT: clustered blastoconidia at septa of pseudohyphae, terminal chlamydospores • CHO: sucrose positive

  16. Candida albicans

  17. Candida stellatoidea • Germ tube: positive • CMT: clustered blastoconidia at septa of pseudohyphae, terminal chlamydospores • CHO: sucrose negative

  18. Candida tropicalis • Germ tube: negative • CMT: sparse single or short-chained blastoconidia anywhere along pseudohyphae, rare chlamydospores • CHO: sucrose positive

  19. Candida glabrata • Causes UTI • Germ tube: negative • CMT: only blastoconidia, no pseudohyphae • CHO: only glucose and trehalose positive

  20. Candida krusei • Germ tube: negative • CMT: tree-like branching of abundant blastoconidia from the septa of elongated pseudohyphae (“cross-matchsticks” appearance)

  21. Candida pseudotropicalis • Germ tube: negative • CMT: branched pseudohyphae with chains of elongated blastoconidia – logs in a stream arrangement of broken up blastoconidia positioned parallel to each other

  22. Candida parapsilosis • Germ tube: negative • CMT: few single or small clustered blastoconidia at or between septa of thin curved pseudohyphae. Sometimes giant pseudohyphae may be observed

  23. Cryptococcus neoformans • Cryptococcosis • Pulmonary • Meningitis • Pigeon droppings

  24. Cryptococcus neoformans • Gram stain • India ink stain

  25. Cryptococcus neoformans • Germ tube: negative • CMT: large, round blastoconidia, no pseudohyphae • Urease: positive (within 3 hours)

  26. Cryptococcus neoformans • Niger seed agar: brown pigment

  27. Cryptococcus neoformans • Cryptococcal antigen test

  28. Geotrichum candidum • Geotrichosis • Mimics Candida infections • Infection in debilitated people • Considered a mold • Germ tube: negative • CMT: arthroconidia andtrue hyphae • Urease: negative

  29. Trichosporon beigelii • Causes White Piedra • Germ tube: negative • CMT: arthroconidia, true hyphae, rare blastoconidia • Urease: positive

  30. Rhodotorula species • Saprophytic yeast found in soil • Rarely a pathogen • Often encapsulated • Urease: positive • Colony pigmentation: reddish-orange

  31. Saccharomyces species • Rarely a pathogen • Ascospores (acid fast positive)

  32. Malassezia furfur • Causes Tinea Versicolor • Septicemia in patients receiving intravenous lipid therapy • KOH: clusters of thick-walled, round budding yeast and short, straight or angular mycelial fragments (spaghetti and meatball appearance) • Lipophilic

  33. In Summary … • Key characteristics of yeast • Identification methods • Germ tube • CMT • Biochemical tests • Clinically significant yeast • Candida albicans • Cryptococcus neoformans

More Related