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- Mold, yeast, or dimorphic
-150 species cause disease
-Wide range of infections
-Macroscopic and Microscopic morphological characteristics
-Carb and extracellular enzyme production(physiological characteristics)
-Clinical picture and epidemiology
agents associated with human disease or hazard; percutaneous injury, ingestion, mucous membrane exposure
indigenous or exotic agents with potential for aerosol transmission; disease may have serious consequences
dangerous or exotic agents which pose high risk of life threatening disease, aerosol transmitted lab infections, or related agents with unknown risk of transmission
Many fungal infections are similar to which other infection and therefore is often ordered with fungal cultures
rapid transport and processing is important because of contamination by...
bacteria and saprophytic fungi
sources for specimens include
respiratory, CSF, blood, cutaneous,urine, tissue, bone marrow, sterile body fluids, urogenital, and wounds
special formations seen mostly in dermatophytes
1. Raquet hyphae
2. nodular organs
3. pectinate bodies (comb)
4. favic chandeliers (antlers)
5. spiral hyphae
Storage units, swollen cells found in pseudohyphae, refractile, appear empty, may be intercalary between blastoconidia of pseudohyphae or terminal (on end of pseudohyphae)
Asexual reproductive cells produced directly form true hyphae, appear to have contents in structure
BHI (Brain Heart Infusion agar)
nutritious, used to get fastidious dimorphs growing ; can add blood or antibiotics
Sabouraud Dextrose agar (SDA)
supports most fungal growth; 4% glucose or 2% glucose in the modified version
You want to give enough_____to grow, but not too much that the fungi don't _______.
Inhibitory Mold Agar (IMA)
selective, primary isolation medial; doesn't grow dermatophytes, has chloramphenicol but not cyclohexamide
Dermatophyte Test Medium (DTM)
screen only, not definitive, pH indicator (phenol red); stimulates conidia formation and pigment formation
Mycosel or Mycobiotic agar
selective for saprophytes; contains cyclohexaminde and chloamphenicol, primary dermatophytes
Cotton Seed conversion agar
used for Blastomyces dermatidis; converts dimorphs from mold to yeast form
Direct exam benefits
allows a preliminary report to physician, may enable fungal therapy, may lead to special media inoculation, may prevent overtreatment
Saline wet mount used for to see...
spherules in Coccidioides immitus
Lactophenol Cotton Blue (LPCB)
Lactic acid- preserves fungal structures
Cotton blue-stains chitin in fungal structures to make them visible
-used for hair, skin, nails, sputum, vaginal, and bronchial washings when a lot of cellular material is present
In the Gram Stain, Cryptococcus neoformans may be overlooded in which 2 specimens?
CSF or respiratory specimens
Modified Kinyoun Acid Fast stain
-ID aerobic, branching GPRs or fungus like bacteria, especially Norcardia species
-uses weaker acid to decolorize: 1%H2SO4
Norcardia appears what color under Modified Kinyoun acid fast stain?
red. everything else counterstains blue
India Ink prep
Use blue/black ink, india ink, negrosin
used for observation of capsules, esp. Cryptococcus neoformans and other encapsulated yeasts appear positive
Calcofluor white stain
dye absorbed by chitin in the fungal cell wall
may be used in conjuction with 10% KOH
Observe this color fluorescence for Calcofluor white stain
bluish white or apple green (depending on wavelength)
Gomori methenamine silver (GMS)
histology; stains fungi and actinomyces; stain black with green background
What stain is better than India ink?
Mayers mucicarmine-stains capsle of Cryptococcus red, the background is yellow
Tease mount advantages
can be performed on a mature colony from a primary isolation plate; can be turned into a permanent mount
Tease mount disadvantage
rough teasing may disrupt conidia and make structural morphology difficult to see
Cellophane tape mount advantage
preserves the integrity of conidia and sturctures more than a tease mount
Cellophane tape mount disadvantage
tape acts as a coverslip, so you can't seal it for permanent mounting
Slide culture method (and advantages)
best method for observation of fungal structures; can be preserved for permanent mounting; two mounts can be preserved by permanent mounting
Slide culture advantage
fungal growth onto the slide and coverslip maintains the morphological position of structures to make ID easier
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