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109 Cards in this Set
- Front
- Back
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Define hyphae
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Long strands of cells which may form mats like mycelium
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What is the appearance of asceptate hyphae? Give an example of a group with asceptic hyphae
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- contain no cross walls
- seen in Zygomycotina - |
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Describe septate hyphae. Give an example of a group with this hyphae.
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- most hyphae are septate
- Ascomycotina - Basidiomycotina - Deuteromycotina |
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Define conidia
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reproductive structures often seen on the end of aerial hyphae
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Define superficial mycoses
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- Top keratin-containing layers of skin or hair.
- Non-invasive - Sometimes described as 'basically asymptomatic' |
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Define cutaneous infections
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- deeper epidermal layers of skin, nails and hair,
- produces more tissue destruction and symptoms than superficial. |
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What are the four superficial mycoses?
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tinea nigra
Pityriasis versicolor Black piedra White Piedra |
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What is the organism responsible for Black Piedra?
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What is the organism responsible for white piedra?
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trichosporon ovoides
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Give examples of cutaneous infections in humans
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Dermato- phytosis
Dermato-mycosis Candidiasis |
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What are the causative agents of Dermatophytosis
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Tricho-phyton spp.
Epidermo-phyton sp. Microsporum sp. |
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What is Dermatomycosis
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a cutaneous mycoses caused by fungi other than dermatophytes
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List dermatophytes
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trichophyton
epidermosphyton microsporum |
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What is the causative agent of the mycosis Candidiasis
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Candidia spp.
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What are the two types of specimens in the mycology lab? what types of specimens are in this group?
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1. cutaneous and keratinised tissue (3)
-skin, hair, nails 2. non keratinised subcutaneous and systemic specimen (6) - tissue bx - blood, - sputum, - urine, - CSF, - bronchial washing |
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What is performed on all specimens. What is rate limiting step in clinical specimens?
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- Microscopy and culture is performed on all specimens as direct microscopy does not rule out disease.
- enough specimen material |
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How is isolation media and direct microscopy performed?
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guided by specimen types - same as bacteriology
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What are the factors which determine whether or not the isolation of fungi is successful?
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1. proper collection
2. quick transport, quick processing 3. appropriate media 4. correct incubation conditions |
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What is the Most rapid method for diagnosis?
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- microscopic examination of material
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what are the mounting fluids for clinical materials composed of?
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- 10% potassium hydroxide
- 10% KOH and glycerol - (UV) 10% KOH, glycerol and calcoflour white |
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How is collection performed for superficial and cutaneous infections?
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from actively growing outer edge of lesion
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How is collection performed for scalp infection
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15-20 hair roots for collection
- due to infection being in the roots - spores are around hair and inside |
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How is collection performed for nails?
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scrape inside of nail and close to nail bed, while removing as much diseased tissue as possible
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How is collection performed for feet?
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Discard outer horny layer and scrape lower layer
also sample between 4th and 5th toes. |
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How is collection performed for tinea
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Discard outer horny layer and scrape lower layer
also sample between 4th and 5th toes. |
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What is the specimen collection procedure for skin scrapings
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- alcohol swab
- advancing border sample - rolling of swab over lesions |
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What is the specimen collection procedure for hair samples
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pluck from shaft
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What is the specimen collection procedure for nail samples
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alcohol
deep scrape to sample tissue recently invaded. |
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What is the turnover time for microscopy?
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<24hrs
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What is the turn around time for culture?
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1-4 weeks
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What are the likely dx for tinea?
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TEM
Trichophyton epidermophyton microsporum |
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What are possible dx for systemic pathogens?
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Fusarium
Scedosporium |
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What are the three dermatophyte genera?
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TEM
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How can dermatophyte genera be made distinct from one another?
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TEM
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Which of the three genera of dermatophytes can infect nails?
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Trichophyton
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Describe the shape and cells in each of the dermatophyte genera
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Which genera in dermatophytes have thick walls?
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Microsporum can have thick or thin walls.
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Which dermatophyte has macroconidia shaped like a
(a) pencil (b) eliptical/spindle (c) club |
trichophyton
microsporum epidermophyton |
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Define arthrophilic and an example of such an infection
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Trichophyton rubrum
only affecting parastisim in humans |
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What are zoophilic infections? give an example
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human infection is from contact with animals. an exampls is microsporum canis
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What is a geophilic infection? give an example
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an infection transferred through soil or contact with soil. Microsporum gypseum is an example.
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Explain host specificity - give an example
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T. concentricum Infections among Europeans are rare. Distribution is restricted to the Pacific Islands of Oceania, South East Asia and Central and South America.
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How do we diagnose dermatophytes?
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Use calcofluor white + 10% KOH
OR --> KOH + Parker ink look for septae and arthroconidia in skin & nails look for spores and hyphae in hair roots |
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define ectothrix
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Endothrix refers to dermatophyte infections of the hair that invade the hair shaft and internalize into the hair cell. This is in contrast to exothrix (ectothrix), where a dermatophyte infection remains confined to the hair surface
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define endothrix
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Endothrix refers to dermatophyte infections of the hair that invade the hair shaft and internalize into the hair cell. This is in contrast to exothrix (ectothrix), where a dermatophyte infection remains confined to the hair surface
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Why is microscopy so important in fungi?
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1. In case it was zygomycosis or cryptococcus
2. Some organisms do not grow in culture 3. will direct the selection of primary isolation media - special media or additional specimens 4. Helps determine the significance when it does grow in culture |
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Describe the calcofluor white + 10% KOH
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- UV fluorescence
- %10 chitin and cellulose binding for the fungal wall. - sensitive |
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Describe KOH and Parker Ink
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- no longer available
- was used most often for direct microscopy - not as sensitive as calcofluor |
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What does 10% KOh do?
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clears tissue and cell debris
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What does 10% glycerol do?
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- prevents crystallisation of reagent
- dyring out of specimen |
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What is the differential characteristic of DTM?
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Dermatophytes produce ammonia which causes a pH change and goes from yellow to red.
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Explain the basic primary isolation conditions for fungi
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- Biosafety cabinets for subcutaneous and systemic fungi (I or II)
- microscopy is performed (Calcofluor + 10% KOH) - 2 to 3 types of media is innoculated - 30 C for 4 weeks - Dimorphic 35 C for 8 weeks - examined 3x weeks |
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How long is the treatment for cryptococcus meningitis
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3 months
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How is Direct Microscopic Examination performed?
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**
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What is the primary isolation media specifically for Dermatophytes?
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What does DTM contain?
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Describe the Isolation of Fungi
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SICI
Safety: subcutaneous and systemic specimens must be processed in Biological safety cabinets Innoculation: variety 2-3 types of media are innoculated. Complimentary: complimentary factors in the media are combined to isolate the fungi Incubation: sealed and incubated at 30 C for 4 weeks, dimorphic at 35C for 8 weeks. |
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List types of PIM for fungi
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Media:
1. No antimicrobials - SDA 2. Antibiotics innoculated - SABP: SDA + blood + polymixin B - SABD: SDA + BHI + chloramphenicol + gentamicin 3. Antibiotic and Antifungals - Mycose/MD: mycobiotic afar + chloramphenicol, gentamicin & cycloheximide. 4. CandidaCHROM |
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What is observed in culture?
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1. Surface colour and reverse colour
2. Typography 3. texture 4. growth rate |
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What temperature do pathogenic dermatophytes grow at?
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35C
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How is identification mainly derived?
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method of spore production
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Identification of Fungi depends on what main characteristics
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1. ability to visualise microscopic conidial features
2. Having a good slide preparation 3. Having a good microscope 4. Macroscopic appearance also assists in Id of fungi (IE: surface and reverse colour) |
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How is Microscopy culture performed?
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cellotape preparation
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What is observed in microscopy culture?
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1. Microconidia shape,
2. Macroconidia shape, thickness of walls, sepate/non spetate 3. Observation of chlamydoconidia defn: thick walled thallic spores formed within the vegetative hyphae for survival. 4. Unique characteristics like spiral hyphae in Trichophyton mentagrophytes |
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What is the following?
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pyriform microconidia
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What is the following?
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sub sperical microconidia
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What is the following?
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spherical microconidia
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Describe the following
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clavate microconidia
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Describe the above morphology
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ellipsoidal macroconidia
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Describe the above
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clavate of bullet shaped macroconidia
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Describe the above
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spindle shaped macroconidia
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Describe the above
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cigar shaped macroconidia
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Describe the above
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irregular shaped macroconidia
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How can macroconidia be described?
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1. wall thickness, wall texture
2. macroconidia shape |
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How can microconidia be described?
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shape
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Identify the above
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characteristic smooth, thin-walled macroconidia, cigar shaped
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Identify the above
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chlamydoconidium
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Identify the above morphology
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thick walled spindle shaped macroconidia
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Identify the morphology of the above
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macroconidia are irregular, spindle-shaped, with rough thick walls
Microconidia are pyriform to clavate in shape |
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Identify the morphology of the above
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ovoid to pyriform macroconidia with 1-3 cells,
relatively thin, finely rough walls, and broad truncate bases |
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What are the four essential steps to the successful isolation of fungi?
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1. clinical suspicion of fungi by GP/ physician
2. Proper collection and transport 3. isolation through innoculation on to correct media and incubation conditions, followed by appropriate staining 4. informed and skilled microscopic examination |
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Identify
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slender clavate to pyroform microconidia. barb wire like - Trichophyton rubrum
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Identify
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T. rubrum - white suede like to downy with a characteristic deep wine reverse pigment.
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Identify
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T. rubrum - scant to moderate number o
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What are the clinical symptoms, locations and terms for T. rubrum?
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CLINICAL SYMPTOMS:
- circular erythematous scaling border - soft wrinkled skin - brittle and discoloured nails - Tinea pedis, Tinea cruris - normally sees growth in 1 week |
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What are the clinical symptoms, microscopic appearance and culture results for trichophyton mentagrophytes?
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clinical:
- scaly, erythematous lesion, scaly. - kerion lesion of scalp with superlative foliculitis - ectothrix infection - does not fluoresce |
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Describe yeasts
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- unicellular
- blastoconidia reproduction - mother cell develops to blastoconidia and separates. - not inherently pathogenic - HME |
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What are examples of yeasts that can become pathogenic?
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Candida
Cryptococcus Malassezia Rhodotorula Trichosporon Geotrichhum |
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What are the two main pathogenic yeasts?
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Malassezia furfur
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What does pathogenic Malassezia furfur cause?
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pityriasis
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Describe the clinical presentation of Malassezia furfur
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- common
- mild - recurrent - pigmentation of redish, brown,white - affect upper trunk, arms and upper body - face legs and hands can be affected - common in the tropics - flaking of the skin/scaling - most commonly seen in caucausions --> hyperpidmentation of the trunk - depigmentation occurs in people of colour called pityriasis versicolor |
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Describe the treatment for Malassezia furfur
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imidiazoles
shampoos |
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Describe the culure of malassezia furfur
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- fluoresces under wood's lamp
- Dixon's media as it requires lipid base, or requires normal media + olive oil layer - 37C incubation |
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Describe the microscopic appearance of malassezia furufr in microscopy and culture
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MICROSCOPY
- thick round oval cells - clusters - short angular hyphae forms CULTURE - small circular colonies pinkish |
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Describe Dixon's agar
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Specialised isolation medium containing glycerol-mono-oleate. oily based media.
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What is the causative agent of white piedra
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trichosporon ovoides
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What is the clinical presentation of white piedra:?
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- light brown, green, red or white soft nodules around beard and moustache
- less firmly attached than black piedra |
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What is the culture method for white piedra
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- SDA at room temperature
- white glabrous colonies within 5 days - wrinkled |
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What is the microscopic appearance of trichosporon ovoides? How is white piedra dx?
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- corn meal-tween 80
- hyaline hyphae - blastoconidia - arthoconidia - biochemical tests |
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What are the main diagnostic features of Trichosporon sp.?
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raised wrinkled colony
arthroconidia basidiomycete class urea positive oval budding yeast celle |
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What class is Trichosporon?
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Basidiomycete
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Identify
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Trichosporon spp.
- oval budding yeast cells |
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Identify
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What other characteristics would we look for here
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urease positive or negative?
culture that is raised and wrinkled colony arthroconidia oval budding yeast cells |
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What is the causative agent of Tinea Nigra?
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Phaeo -annello- myces wernicki
phaeannellomyces wernicki |
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What is the clinical presentation of tinea nigra?
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brown to black
non scaly patches hands |
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What cultural media and procedure is used to isolate tinea nigra. What are we likely to see?
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SDA
room temp Black yeasty colony - initial slow growth short olive grey mycelium turn to olive as aerial mycelia develop |
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Describe the microscopic characteristics of phaeoannellomyces wernecki
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brown to dark
septate hyphae 2 celled yest cells annelloconidia |
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Describe the microscopic characteristics of phaeoannellomyces wernecki
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