Mycology and diagnostics Flashcards
What are the characteristic of Fungi as a kingdom?
eumycota, eukaryotic, ergosterol cell membrane, cell wall- glucans and chitin, heterotrophic metabolism (need to be fed)
What are the morphologies of fungi? subclasses?
yeast, mold- fleshy fungi (mushroom- reproductive structure)-> terranean and subterranean and dimorphic- yeast or mold depending on environmental conditions (typically temp)
What are the morphologic features of mold?
unicellular, non-filamentous (budding cells- trying to reproduce or pseudohyphae= elongated bud)
What are the morphological features of mold (mould)?
multi-cellular, fiamentous- hyphae (septate or non-septate) and mycelium (interwoven mass of hyphae)
What is a conidia? What doe sthe color of mold growing tell you?
a mold spore; white= less likely spores are being released, color change= spores being released
What are mushrooms?
aerial reproductive structure, hyohae in soil; basidium with basidiospores
What are the morphologic features of dimorphic fungi?
mold at room temp (environmental form), infectious via inhalation, yeast t body temp (37C), diagnostic form, presumptive in vivo, not infectious
What is taxonomy?
reproductive structure (basis for ID and classification, which determines pathogenesis and epidemiology, name of disease, only see vegetative in vivo (require in vitro culture to ID by repro struct.), rare to see repro structures in vivo
How are fungi named?
generally 2 names: anamorph (asexual name, in vivo-lab) and teleomorph (sexual, prefect state, see both in vitro)
what are general features of asexual structures? examples in mold? yeast?
involve mitosis; arthroconidium, macroconidium, microconidium, and sporangiospore; blastoconidium and chlamydoconidium
what are the features of a arthroconidium? Characteristic species?
within hyphae, rectangular to barrel-shaped cells; coccidioides immitis
What are the features of microconidium? Macrocondium? Characteristic species?
smaller of two; larger of two, usually multicellular; demratophytes
What are the features of a sporangiospore? Characteristic species?
produced with a sporangium; rhizopus spp.
What are the features of blastoconidium? characteristic species?
produced by yeast cells, “budding”; all yeast
What are the features of chlamydoconidium? characteristic species?
tip of psuedohyphae, ID for candida albicans (most common disease causing) and candida dubliniensis
what are the general features of sexual forms of reproductive structures? examples?
involve meiosis; can involve mating of two different fungal strains of same species (compatible) or ability to produce structure without mating (hermaphroditic, male and female); acospore, basidiospore, zygospore
What are the features of acospores? characteristic mold species? yeast?
spores within an ascus; pseudallescheria boydii, hermaphrodite, sexual name; saccharomyces cerevisiae, hermaphrodite, sexual name
What are the features of zygospores? characteristic species?
naked spores; rhizopus spp. requires mating (asexual name same as sexual)
What are the features of basidiospores? characteristic species?
formed on basidium (mushroom), amanita spp., hermaphroditic, no asexual state
what is the basis of fungal classification?
nature of sexual spores orlack thereof, hyphal characteristic (septate or not)
What are the phylum under eumycota? classes under?
Perfect Fungi- zygomycota (produce zygospores), Ascomycota (ascospore and septated hyphae), basidiomycota (mushrooms); and Imperfect Fungi- deuteromycota
what are the methods of direct detection in the lab?
gram stain, calcofluor white stain, KOH prep, Wet mount, Woods Lamp, India Ink stain; and histopathology
what are the features of gram staining fungi?
yeasts- gram (+), mold- stain poorly
What are the features of calcofluor white stain?
stains chitin in fungal cell wall, need fluorescence microscope
What are the features of KOH?
same as draino, chews up proteins, use with keratinized tissues- skin, hair nails, look for dermatophytes (ringworm)
What are the features of Wet mount?
oral or vaginal secretions, budding yeast= usually thrush; turn light down to see
What are the features of Wood’s Lamp?
UV light, fluoresce dermatophytes and demratophytosis (ringworm, esp in hair)
What are the features of india ink stain?
CSF, encapsulated yeast, cryptococcosis (cryptococcal meningitis from cryptococcal neoformans, very common in immune compromised)
What are the features of histopathology?
GMS (gemori methenamine silver) stain= mold w/ hyphae; Mayer’s mucicarmine stains yeast pink (mucin capsule, Cryptococcus neoformans); PAS (periodic acid-Schiff) stain- yeats and mold inernal structures (pink)
What medium is selective for fungi? fetaures of it?
Sab (Sabouraud dextrose agar), low pH, nutrionally deficient, 2+ days yeast, 7+ days mold, may take 4 wks, forces sporulation, and weeds out B
What is a biochemical test that can be performed for yeast?
germ tube test, ID candida albicans/dubliniensis, has candida albicans complex, grow culture 48 hrs, put in complex and incubate 2-3 hours, lateral hyphal extension is positive
What are the features of mold ID from culture?
culture medium growth characteristics, hyphal structure (septate or not), reproductive structures, requires well trained eyes
What are the features of serologic diagnosis of fungi?
Ab- not reliable or useful in immunocomprimised or neutropenic; Ag- latex agglutination- cryptococcal Ag in CSF for following treatment, and Serum galactomannan- Ag from aspergillus hyphae, not great, adjunct to follow therapy
What are some methods of culture confirmation?
nucleic acid probes (only approved for lab grown culture not tissue specimen, not cheap) and sequence analysis comparison- must have pathogen in mind, undergoing eval
What are the different main categories of fungal pathogenesis?
true pathogen- problem with even normal immune system, opportunistic- only problem in immunocomprimised
What are the factors behind fungal ability to cause disease?
colonize host, suitable micro-environment niche, avoid or subvert host normal defenses, multiple in environmental niche
What are known factors of fungal virulence?
highly researched don’t know much;grow at 37C and physiologic pH 7.3, produce proteinases- keratinase, phospholipase
What aspects of immune system play a role in fungal infections?
phagocytes primary role (if neutropenia at inc. risk), cell mediated (Tcells major) and humoral (B cells minor)
What is mycetismus?
poisoning by ingestion of fruiting bodies (mushroom poisoning)
What is mycotoxicosis?
intoxication by eating food contaminated with toxin produced by mold (aflotoxin), big problem as it is heat labile
What is hypersensitivity disease?
inhalation of fungal elements induce hypersensitivity (pneumonitis)
What is mycoses?
infection caused by a fungus
what are the classifications of mycoses?
superficial, cutaneous or mucocutaneous, subcutaneous and systemic
What is involved in a superficial mycoses? examples.
restricted to outermost skin layers, stratum corneum; Pityriases (tinea) versicolor (dry scaly ringworm, pigmented), Dandruff
What are the etiology, distribution, predisposing factor, clinical picture of Pityriasis?
malassezia furfur (flaky, lipophilic yeast), part of normal flora (endogenous, over grow), oily skin, hypopigmented lesion if tan (dark if fair complected, catheter associated malassezia sepsis),
What is the etiology, distribution and predisposing factors of dandruff?
Malassezia globosa, found on human scalp, oily skin - sebaceous secretions, higher levels of M. globosa on scalp, individual susceptibility
What are the features of cutaneous mycoses? Examples.
infect keratinized tissues w/o invasion (skin, hair, nails); candidiasis (thrush) and dermatophytes (ringworm-tinea)
skin scraping, culture and biochemical features of Pityriasis?
spaghetti and meatball appearance, lipid growth requirement (olive oil overlay), and sugar assimilation tests; dumbbell appearance
What is the etiology, distribution, and predisposing factors?
candida albicans most common, normal flora (endogenous to mouth, skin, GI, and vaginal; except mom to baby), endocrine deficiency, immune defect (chemo, steroid, AIDS), follow Ab therapy
What are the clinical features of candidiasis in mucous membranes? Vaginal mucosa?
curd-like patchy areas, inflammation and swelling (drool and talk funny); thick milky discharge, inflammation and itching
How is candidiasis diagnosed?
wet mount, gram stain, look for yeast; culture- chlamydoconidia to ID C. albicans/dubliniensis, biochemical- germ tube to ID C. albicans/dubliniensis, sugar assimilation tests or thermotolerance, separate species
What are the etiologies of dermatophytosis?
epidermophyton floccosum, Trichophyton rubrum, Trichophyton tonsurans, and microsporium canis (all ringworm)
What is the distribution and predisposing features of dermatophytosis?
True pathogen, selective association of pathogens (animal, human, soil); exposure to contaminated object
What are the clinical presentations of skin dermatophytosis? diagnose?
dry and scaly skin leading to vesicular lesions, tinea corporis (body), tinea pedis (athletes foot), tinea cruris (jock itch); KOH prep
What are the clinical presentations of hair dermatophytosis? diagnose?
brittle hair, with or without alopecia, inflammatory response in severe infections, Wood’s Lamp
What are the clinical presentations of nail dermatophytosis? diagnose?
deformed and/or cracked nail (tinnea anguium), hardest to treat; difficult due to smaple thickness but KOH
How is dermatophytosis diagnosis confirmed in general? Features of trichophytun rubrum? microsporum canis? epidermophyton floccosum?
culture, macroscopic features: macrocondium, microconidium, septate hyphae; red pigment in culture; septate hyphae from dogs or cats; flocks (tinea corporis and cruris)
What are the general features of subcutaneous mycoses? example.
localized area (SQ or lymphatics, hands or feet most common), traumatic implantation, exogenous fungi (vegetation); sporotrichosis (US, other species in other countries)
what is the etiology, distribution and predisposing factor with sporotrichosis?
sporothrix schenkii (dimorphic), moss, hay, soil, decaying vegetation, exogenous source exposure
What are the clinical features of sporotrichosis?
lessions at inoculation site (multiple nodules, lymphatics that drain inoculation site), “lymphocutaneous”, raised local lymphadenopathy that necrosis over time
What is the presumptive diagnosis of sporotrichosis?
clinical picture and/or histopathology (GMS) elongated yeast called cigar bodies
What is the confirmed diagnosis of sporotrichosis?
culture at 25c (yeast bud like)and 37c (hyphae)
What are the general features of a true systemic mycoses? Examples
normal host immune system, lungs primary inoculation (spore inhaled), disease spectrum widespread (acute, chronic, or systemic), granulomatous, geo restricted (soil), etiologic agents dimorphic; endemic fungal disease- blastomycosis, histoplasmosis, coccidioidomycosis
What us the etiology, distribution and predisposing factors of blastomycosis?
blastomyces dermatitidis, endemic soil- Northern missisisspi river basin, exposure to conidia from soil (inhaled), some gentic predisposition affecting severity of disease
What are the clinical features of blastomycosis?
primary pulmonary disorder (frequently unrecognized, very mild), potential to disseminate to skin, bone, and GI
How is blastomycosis presumptively diagnosed?
clinical picture and/or histopathology, GMS or H&E, broad based budding yeast with double contoured wall
How is blastomycosis diagnosis confirmed?
culture 25C (hyphae) and 37C (double contoured wall with broad based budding); slow grow, microscopic observation, DNA probe
What is the etiology, distribution, and predisposing factor for coccidioidomycosis?
coccidioides immitis/posadasii (can’t distinguish, nationally reportable), soil (SW US), exposure to conidia from soil by inhalation, normal host (haboobs!)
What are the clinical features of coccidioidomycosis?
primary pulmonary disease, extrapulmonary brain infection in AIDS (defining)
How is coccidioidomycosis diagnosed presumptively?
clinical picture and/or histopathology- spherule with endospores (yeast like but not technically yeast, can look like budding yeast is only find endospores) H&E or GMS
How is diagnosis confirmed for coccidioidomycosis?
culture (highly infectious in lab, bio3, capped tubes) microscopic observation (classic arthroconidia), DNA probe, DNA polymorphisms to separate immitis (California clade) from posadasii (non-California clade), noninfectious in hospital (dimorphic)
What is the etiology, distribution and predisposing factor for histoplasmosis?
Histoplasma capsulatum (intracellular in histocytes), endemic in soil of Ohio-Missouri river valleyassociated with bird and bat droppings (high nitrogen content in soil), exposure to conidia- inhalation normal host
What are the clinical features histoplasmosis?
primary pulmonary (coin lesions bilateral), extrapulmonary- blood (fungemia) and lymph nodes (AIDS defining)
How is histoplasmosis presumptively diagnosed?
clinical picture and/or histopathology, characteristic CXR, small intracellular yeast (PAS)
How is histoplasmosis diagnosis confirmed?
culture, microscopic observation (characteristic tuberculate macroconidia at 25C, small budding yeast at 37C), DNA probe
what are the features of opportunistic systemic mycoses in general?
invasive infection (fungi low virulence), immune defect (aggressive cancer therapy older population, solid organ transplant, AIDS)
Examples of opportunistic systemic mycoses.
true yeast or yeast like - systemic candidiasis, cryptococcosis, pneumocystis pneumonia; true mold- mucomycosis (zygomycosis) and invasive aspergillosis; (same in vivo and in vitro, any temp for all)
What is the etiology and distribution of invasive candidiasis?
canidida albuicans/dubliniensis, C. glabrata (resist std antifungals), C. Krusei (intrinsic resist fluconazole), C. lusitaniae (intrinsic resist amphotericin B), C. tropicalis, and C. parapsilosis; endogenous flora
What are the clinical features of invasive candidiasis?
any organ system (Resp- AIDS def., Wound- pulm or peritoneal, and Esophageal- AIDS def.), Candidemia (blood, diagnose with blood culture)
How is invasive candidiasis presumptively diagnosed?
clinical suspicion, gram stain blood culture and or histopathology- budding yeast with pseudohyphae
How is the diagnosis of invasive candidiasis confirmed?
culture, biochemical testing (germ tube to rule out C. albicans/dubliniensis
What is the etiology, distribution, and predisposing factor for cryptococcosis?
Cryptococcus neoformans (encapsulated yeast), environment assoc. w/ pigeons, exogenous- inhalation dried fecal material from colonized pigeons, immunosupression
What are the clinical features of cryptococcosis?
primary pulmonary, extrapulmonary (AIDS def.)- blood (fungemia), brain (meningitis), and Cutaneous
How is cryptococcosis presumptively diagnosed?
clinical suspicion, india ink stain of CSF, histopathology- PAS, encapsulated budding yeast, irregular sizing
How is the diagnosis of cryptococcosis confirmed?
culture- mucoid colonies, biochemical tests
What is the etiology, distribution, and predisposing factor for Pneumocystis Pneumonia?
Pneumocystis jirovecii (formerly P. carinii f.sp. hominis), human derived, environmental source not recognized, immunosuppression (AIDS)
What are the clinical features of Pneumocystis Pneumonia?
primary pulmonary (AIDS def.)- nonproductive cough, chest tightness, CXR- diffuse bilateral interstitia and bilateral perihilar interstitia
How is Pneumocystis Pneumonia presumptively diagnosed?
clinical picture (characteristic CXR) and compromised host
How is diagnosis of Pneumocystis Pneumonia confirmed?
histopathology (lung biopsy- crescent shaped cysts), can’t culture, immunoflourescent stain (bronchoalveolar lavage, monoclonal Ab against surface epitopes)
What is the etiology, distribution, and predisposing factor for mucormycosis (zygomycosis)?
Rhizopus spp. or Rhizomucor spp., environment saprophytes (everywhere!), sever immune suppression, uncontrolled diabetes (low blood pH encourages growth)
What are the clinical features of mucormycosis (zygomycosis)?
primary sinus orbital (have to cut out), disseminate to any organ system (extremely deadly)
How is mucormycosis (zygomycosis) presumptively diagnosed?
clinical suspicion and/or histopathology- irregular sized non-septate hyphae, angioinvasive
How is the diagnosis of mucormycosis (zygomycosis) confirmed?
culture, microscopic appearance- aspetate hyphae with sporangium containing sporangiospores and rhizoids (roots), and species ID- mating studies and molecular sequencing
What is the etiology, distribution, and predisposing factor for invasive aspergillosis?
aspergillosis fumigatus complex, A. Flavus complex, and A. terrus complex, environmental contaminate- sparophyte (breath in), immune suppression (neutropenia)
What are the clinical features of invasive aspergillosis?
primary pulmonary and cutaneous (under tape), sino-orbital, disseminated
How is invasive aspergillosis presumptively diagnosed?
clinical suspicion, histopathology- 45 degree angle branching, irregular size, septate hyphae
How is the diagnosis of invasive aspergillosis confirmed?
culture, microscopic features- 45 degree angle branching, irregular size, septate hyphae, vesicle, phialides, conidia; molecular sequencing
What is the etiology, presentation, and predisposing/distribution of fungal meningitis/septic arthritis?
exserohium rostratum- opportunistic fungus, black pigmented (phaeohypomycosis), contaminated steroid injection (compounded solution)
