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Mycology lab
Mycology quiz one
| Question | Answer |
|---|---|
| What type of laboratory precautions are required? | Gloves, mask, and gown Class II biosafety cabinet |
| Why are class II biosafety cabinets required? What must be done daily? | Because of airborne spores/conidia & for all processing and plating. Airflow must be checked daily |
| Define conidia | Spore produced asexually by fungi at tip of a specialized hypha |
| What types of media is used and which one is preferred? | Screw cap tubes & Petri plates. Screw cap tubes are preferred |
| why are screw capped tubes preferred? | 1. It decreases airborne spores 2. Smaller surface area for fungal growth 3. Preserves moisture |
| Why are petri plates used and what must be done each time you use it? | 1. Greater surface area for fungal growth 2. Easier to manipulate fungal colonies. You must seal plates with air-permeable tape. |
| What is needed for laboratory identification and what types of specimens are collected? | Proper collection, handling, & transport is dependent on body site: Hair, skin, nails, urine, genital tract, respiratory specimens, wounds & lesions, blood & bone marrow, and CST |
| What are the types of direct microscopic exams? | Saline wet mount, Lactophenol cotton blue, Potassiom hydroxide (KOH), Calcofluor White with KOH, India Ink Prep, & tissue Stains |
| Why is it important to perform direct wet mount examination on every specimen submitted for fungal culture? | it allows you to send out an immediate preliminary report to the physician, if it’s positive you can inoculate special media to quickly isolate & specifically id the organism. As well it could save the patients life if the patient has an acute disease. |
| Explain Saline Wet Mount | 1. Place one drop of specimen on a glass slide & add one drop of saline. 2. Put on coverslip & observe under low & high power using low light. Organism will appear refractile, or shiny, and slightly green. |
| What type of fungal elements will you observe on a saline wet mount? | Budding yeast, hyphae or pseudohyphae, & conidia |
| Saline Wet Mount Picture | Fusarium sp. |
| Why is Lactophenol Cotton Blue used? | Phenol Kills Fungi Lactic acid preserves fungi elements Cotton blue stains chitin in fungal cell walls |
| Lactophenol Cotton Blue | Microsporum gypseum |
| Potassium hydroxide prep procedure | 1. Mix 10& KOH with specimen 2. Heat gently & Incubate 20 min. 3. KOH dissolves keratin & other cellular material 4. KOH doesn't dissolve chitin 5. Glycerol prevents reagent crystallization 6. Used for skin, hair, nails, & tissue |
| KOH prep | Paracoccidioides brasiliensis (thoracic mass) |
| Procedure for Calcofluor White with KOH & why it's used | Mix fluorescent with KOH The dye binds to chitin in cell walls See apple green or blue-white fluorescence depending on filter |
| Calcofluor White with KOH | Blastomyces dermatitidis |
| Calcofluor White with KOH | Candida albicans germ tubes |
| India Ink Prep | Mix specimen with India Ink or nigrosin. Used to observe for capsule with maximum light In CSF, may be diagnostic for Cryptococcus neoformans |
| India Ink Prep pic | Cryptococcus neoformans |
| Tissue Stains | Periodic Acid-Schiff (PAS) Gomori methenamine silver (GMS) Giemsa Acid-fast stains |
| Tissue Stains pic | Coccidiodesimmitis spherules PAS |
| Tissue Stains Pic | Pneumocystiscarinii (jiroveci) GMS |
| Tissue Stains Pic | Histoplasma capsulatum Giemsa |
| Nonselective Media | Sabouraud Dextrose Agar (SDA or SabDex), Sabouraud Brain Heart Infusion Agar (SABHI), Brain heart infusion agar with Blood (BHIB) |
| Sabouraud Dextrose Agar | pH 5.6 Nutritionally poor inhibits most bacteria some fungi won't grow |
| SDA | Aspergillus fumigatus Candida albicans |
| Sabouraud Brain Heart Infusion Agar (SABHI) | not as nutritionally poor allows most fungi & Bacteria to grow |
| Brain Heart Infusion agar with Blood (BHIB) | nutritionally rich and good for sterile sites (CSF, blood) |
| Selective Media | Inhibitory mold agar (contains gentamicin), BHIB with gentamicin & chloramphenicol, BHIB with gentamicin, chloramphenicol, & cyclohexamide, or Dermatophyte Test Medium (DTM) |
| Inhibitory Mold agar | contains gentamicin and inhibits bacteria |
| BHIB with gentamicin & chloramphenicol | increased nutrients inhibits bacteria and fungus-like bacteria |
| BHIB with gentamicin, chloramphenicol, & cyclohexamide | increased nutrients, inhibits bacteria, fungus-like bacteria, yeasts, & fungal oppourtunist |
| Dermatophyte Test Medium (DTM) | Dermatology offices Contains antibiotics & phenol red Pos: Color change from yellow to red |
| Special/Subcultured Media | Birdseed or Caffeic Acid Agar, Potato Dextrose Agar, Neutral SDA or SabDex (Emmon's modification) |
| Birdseed or Caffeic Acid agar | Cryptococcus sp. produce melanin |
| Potato Dextrose Agar | promotes mold sporulation & pigmentation |
| Neutral SDA or SabDex (Emmon's modification) | neutral pH & less glucose better for culture maintenance |
| What types of temp and humidity do fungus like? | 30 although 25 (room temp) is acceptable 37 to demonstrate mold to yeast conversion 40-50% humidity seal plates with air-permeable tape and loosen screw caps on tube |
| What is the incubation time? | Growth rates vary (days to weeks) |
| How long do you keep cultures for? | at least 1 month |
| How long do you keep Histoplasma capsulatum cultures for? | 12 weeks. |
| What are the 3 types colony (Macroschopic) morphology of fungus? | Texture, topography, & Color |
| Define texture | height of the hyphae |
| Define Topography & types | Surface features Rugose Umbonate Verrucose Flat |
| What is this type of topography | Rugose - furrow radiating from center |
| What is this type of topography | Umbonate - buttonlike |
| what is this type of topography? | Verrucose - wrinkled |
| Color of colonies | Characteristic surface and reverse, usually different colors on the front from the back. |
| Colonies with different colors | Trichophyton rubrum |
| What are the types of microscopic morphology? | Hyphae septate vs, aseptate Hyaline vs. dematiaceous Conidia/spores |
| Conidia/Spores to differentiate by | type Size shape arrangement |
| Hyphae septate vs. aseptate | |
| Hyaline vs. Dematiaceous | Penicillum sp. & Bipolaris sp. |
| Blastoconidia | budding |
| Poroconidia | Pushing |
| Phialoconidia | tube or vase shaped |
| Annellocondidia | Ringed or saw-toothed |
| Macro/microconidia | entire hyphae converts |
| Arthroconidia | fragments |
| Sporangiospores | only in Aseptate hyphae |
| Chlamydoconidia | survival conidia (like bacteria) |
| Types of culture examination | Tease mounts, Cellophane tape prep Slide culture |
| Tease Mount | Drop of LPCB onto slide use needle to tease part of colony to slide Tease apart with second needle Coverslip Adv: can be performed immediately after growth Disadv: teasing disturbs morphology |
| Cellophane Tape Prep | Drop of LPCB onto slide Touch top of colony with tape Place tape onto slide ADV: can be done immediately, doesn't disturb structures DIS: Easiest to use with plates |
| Culture using tape prep | Aspergillus fumigatus |
| Slide Culture | Inoculate agar block in slide culture setup with organism Add coverslip & sterile water for moisture Incubate for growth Coverslip: transfer to slide with drop of LPCB Slide: Remove agar; add LPCB & coverslip |
| Slide Culture pic | Adv: Fungal elements grown, very little disruption of morphology DIS: requires technical expertise Incubation period for growth of the subculture |
| Slide Culture pic | |
| Opportunistic pathogens- immunocompromised Patients | Inherited genetic defect Acquired - HIV/AIDS, certain cancers Medications - steriods, chemotherapy, radiation, immunosuppressive post-transplant medications, pregnancy |
| Mucormycosis (zygomycosis) | infection mostly affects the nose, sinuses, eyes, & Brain without early diagnosis & treatment, mucormycosis can damage the face so badly that the required surgery results in disfigurement. Death in 2-10 days (total) |
| Zygomycetes (aseptate fungi) | grow very fast |
| LPCB tape prep | Mucor sp. |
| LPCB tape prep | Rhizopus sp. |
Created by:
Twixy565