Diagnostic Methods and DermPath Flashcards
Special stain(s) that highlight collagen
Masson’s trichrome
Special stain(s) that highlight elastin/elastic fibers
Verhoff’s Elastic Stain
Special stain(s) that highlight melanin
Fontana-Masson; Gomori methenamine silver stain
Special stain(s) for calcium
VonKossa Stain
Special stain(s) for lipids
Oil Red O
Special stain(s) for acid-fast bacteria
Ziehl-Neelsen, Kinyoun’s method, Fite stain, Auramine stain
Special stain(s) for fungi
Gomori methenamine silver stain, Periodic acid-Schiff
What components of a sample does hematoxylin stain? What color?
Is a basic dye with a purplish blue color that stains ACIDIC structures such as the cell nucleus and organelles that contain RNA such as ribosomes and rough endoplasmic reticulum – stains them PURPLE
What components of a sample does eosin stain? What color?
Is an acidic dye that stains BASIC structures such as the cytoplasm, cell walls, and extracellular fibers – stains them REDDISH PINK
What is the Giemsa stain used for?
useful in identifying parasites or pathogenic bacteria; used in blood films including peripheral blood smears and bone marrow aspirates
What structures are Congo red stains used for?
amyloid fibrils (gives apple-green birefringence under polarized light); stains cell wall of fungi and outer membrane of gram-negative bacteria
What accounts for the different colors between gram-negative and gram-positive bacteria when a gram stain is applied?
Gram positive = thick peptidoglycan layer in cell wall that retains crystal violet stain; Gram negative = thinner peptidoglycan layer allows the crystal violet to be washed away when ethanol is added, then pick up the pink/red counterstain instead
Give 8 differentials for infectious organisms associated with Splendore-Hoeppli reactions on biopsy
Zygomycosis (Rhizopus, Mucor, Basidiobolus, Conidiobolus), Habronema (and other cutaneous larval migrans), Sporotrichosis, Blastomycosis, Aspergillosis, Dermatophytic/Bacterial pseudomycetomas, Nocardiosis, Actinomycosis, Pythiosis (not as striking), Lagenidiosis (not as striking)
What is the Splendore-Hoeppli reaction?
brightly eosinophilic material that surrounds organisms – represents an antigen-antibody reaction around infectious agents or parasites; occurs at the periphery of organized aggregates of organisms
What are the components of the DiffQuick staining solution?
Methanol = clear or pale blue fixative; Eosin = red dye; Methylene blue = blue dye
Explain how the D forms in a D test. What enzyme change occurs?
Diffusion of erythromycin in the plate closer to clindamycin results in induction of
methylase (which alters the 50S subunit on the ribosome which both antibiotics bind to in
order to kill the bacteria); The Zone 1 bacterial resistance creates the “D shape” and does not spread farther because
higher concentrations of clindamycin reach the inner zones (Zone 2) and inhibit bacterial growth before the erythromycin can induce resistance in the bacteria to clindamycin as well
What is the mechanism of action of methanol as a fixative in staining?
It is a denaturing fixative = removes water from cells and preserves secondary structure
while altering tertiary structure
What bacteria can fluoresce with a Wood’s lamp?
Pseudomonas aeruginosa and Corynebacterium minutissimum (but NOT characteristic apple-green of dermatophytes)
What is the difference between ectothrix vs endothrix invasion with dermatophytes
Ectothrix = hyphae in the hair shaft form arthroconidia on the hair surface; Endothrix = hyphae in the hair shaft form conidia within the hair shaft leaving the cuticle
intact
What species of dermatophytes cause ectothrix invasion?
Microsporum gypseum, Trichophyton verrucosum, T. mentagrophytes
What species of dermatophytes cause endothrix invasion?
Trichophyton tonsurans
What are 3 fungi that won’t grow on a DTM plate? Why?
They are sensitive to cycloheximide; Cryptococcus neoformans, Candida spp., Aspergillus spp., Zygomycetes (Rhizopus, Mucor spp., Basidiobolus, Conidiobolus)
A pigmented fungal organism is present on biopsy, but is not a dermatophyte. What is your next most common differential?
Aspergillus
What is Dunstan’s blue line?
area of stratum corneum lifted by degenerate neutrophils and cocci, indicating a staph infection
How is direct immunofluorescence staining performed?
incubate cells with an antibody directly conjugated to a
fluorochrome
How is indirect immunofluorescence staining performed?
cells are incubated first with a primary antibody, then
again with a secondary fluorochrome-labeled antibody
Define immunohistochemistry
antibodies specific for certain epitopes applied to histopathology sections
Diagnostic that evalutes tissue samples for presence of intralesional immunoglobulins and/or complement factors using fluorescent-coupled antibodies
Direct immunofluorescence
Diagnostic that uses Immunohistochemistry or immunofluorescence to evaluate autoantibodies revealed on the lamina lucida or lamina densa in the basement membrane
salt-split skin
Diagnostic that evaluates fixed samples ultrastructurally to identify cellular and extracellular matrix changes
electron microscopy
Diagnostic that uses complementary molecular probes to detect sequences of certain chromosomal regions or genes (DNA or RNA), typically on fixed tissue
in situ hybridization
Diagnostic that evaluates sera for the presence of tissue specific circulating autoantibodies
indirect immunofluorescence
What stain highlights glycogen, mucopolysaccharides, fungi, and tissue debris as red?
Perioidic-Acid Schiff
What stain highlights lipids as red?
Oil Red O
What stain highlights elastin as black?
Verhoff’s Elastic Stain
What stain highlights lipids as green-black?
Sudan black B
What stain highlights acid mucopolysaccharides (mucin) as blue?
Alcian blue
What stain highlights acid mucopolysaccharides (mucin) and mast cell granules as purple?
Toluidine blue
What stain highlights fungi and melanin black?
Gomori methenamine silver stain
What color does Gram stain vs Brown-Benn stain highlight gram-postive and gram-negative bacteria?
Gram-postive: Gram stain = purple, BB = blue; Gram-negative: Gram stain = red, BB = red
Define prevalence
proportion of cases in a population that have a disease at a given time
Define incidence
probability of a disease occurrin in a population over a defined period of time
