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69 Cards in this Set
- Front
- Back
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the wide variety of fungal infections is due to:
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-their diversity as a group
-host immunity or lack thereof -tissue(s) affected/infected -geographical location -virulence factors |
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Fungi are _________ meaning they require exogenous carbon as a food source.
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heterotrophic
---therefore they recycle nutrients in the ecosystem |
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In the overlying scheme of fungal disease they:
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1. have overlapping clinical signs and presentations
2. are treated with a special class of drugs 3. may be challenging to diagnose 4. Can be a sentinel for human disease |
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What are some beneficial effects of fungi?
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decomposition - recycle carbon and nutrients
can be biosynthetic factories used to produce alcohol, drugs, antibiotics model organisms for biochemical and genetic studies |
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The fungal cell wall is _________, like a plant, so it is non motile. Protozoa and animals have cell walls that are not _________.
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fungal cell wall is rigid
protozoa and plant cell walls - not rigid |
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The cytoplasmic membrane of a fungus contains the sterol _________ (a target for some antifungals) while the cell wall is comprised of _______ (vs. cellulose in plant cell walls).
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cytoplasmic membrane - Ergosterol
cell wall - chitin |
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Chitin
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composes the cell wall of fungi
is a complex carbohydrate and is very resistant to degradation |
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Fungi are _________ cells, as opposed to bacteria which are ________.
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fungi = eukaryotic
bacteria = prokaryotic |
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Fungi are for the most part ___________ to antibacterial agents.
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resistant
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Fungi lack ____________ so they cannot perform ________________ to produce their own organic molecules. Fungi secrete digestive enzymes to break down organic molecules the fungi can then absorb. Therefore they are _________.
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chloroplasts
photosynthesis heterotrophs |
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Most fungi consist of thread-like filaments (few are unicellular e.g. rapid rise yeast), these are known as...
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Vegetative hyphae - they elongate into a food source and absorb the nutrients
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Mycelium
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a mass of vegetative hyphae -- by elongating and often branching, the fungi increase their surface area for absorption
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fruiting bodies
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reproductive hyphae arising from hyphae; they are involved in the dispersal of fungal spores (since they are light, they are easily dispersed throughout the environment)
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once fungal spores disperse....
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they can quickly 'spread' especially if the environment is full of nutrients
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How is the ability of fungal spores to disperse in the environment important to veterinary medicine?
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the easily dispersed spores can be inhaled by the animal (or a person); inhaling the spores can lead to disease
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How do fungi reproduce?
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they reproduce both sexually and asexually (ie the spores can be produced either way)
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Why does it matter how fungi reproduce?
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--Because it helps with classification
---Because it impacts ability to spread as well as allowing genetic diversity which impacts survival (of both host and fungus) |
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How are fungi classified?
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they are classified into phyla according to the type of fruiting body and the sexual spores they form
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Explain the process of asexual reproduction of fungi
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spores form at the tips of reproductive hyphae via asexual reproduction (ie mitosis). -- because there are millions of reproductive hyphae, asexual repro allows the fungus to release many, many spores that can then germinate and utilize available nutrients
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Explain the process of sexual reproduction of fungi
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because this involves the process of meiosis, crossing-over can occur - this enables new combinations of genes to be carried by the offspring; this can provide an advantage by possibly giving the offspring new traits; also maintains gene flow w/in the population allowing new traits (advantageous ones) to spread quickly throughout the population
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What are the two morphological types that fungi can be classified as?
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Yeasts
Mold (septate or non-septate) |
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Examples of Yeasts
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- Candida albicans, Cryptococcus neoformans, malassezia pachydermatis
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Descriptive info of yeast
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-- unicellular, oval or spherical cells
--reproduce asexually to form daughter cells which develop as small outgrowths or buds from the older parent cell --some may produce pseudohyphae -really just elongated cells that remain attached to each other and may resemble hyphae |
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What is the appearance of yeast colonies and how do you identify them?
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-usually moist or mucoid, similar to bacterial colonies
-identified by biochemical tests |
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What is a thallus?
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this is the resultant colony when there are many hyphae present; in the center, hyphae are often necrotic due to deprivation of nutrients and oxygen
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What is the principal element of a mold?
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the hypha (or mycelium) which is a branching tubular structure 2-10 um in diameter
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What are the 2 structural types of hyphae?
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Septate and non-septate
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septate hyphae
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-have cross walls (or septae) along the hypha to divide it into compartments but not into cells
-more robust than non-septate b/c if a hypha is damaged pores between adjacent compartments can be plugged preventing the death of the whole strand |
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Molds
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hyphae
branching, filamentous septate or non-septate highly variable |
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In which type of fungi are septate hyphae typically found?
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Ascomycetes, Basidomycetes, and Deuteromycetes
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Non-septate fungi
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-no cross walls
-considered more primitive b/c if hyphal strand is damaged the entire strand dies -this is important when trying to culture from tissues -typically belong to the Zygomycetes (which are bad!!) |
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What are the 2 main functional types of hyphae?
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vegetative and aerial
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What are vegetative hyphae?
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they project into the substrate for nutrients
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What are aerial hyphae?
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they project into the air. They often bear reproductive cells or spores. The mode of spore formation and the structure, size and shape of the spore is used for classification.
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Medically important fungi are usually divided into?
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the perfect fungi (commonly found in the sexual state) and fungi imperfect which are invariably found in their asexual state
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What are "perfect" fungi?
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those fungi commonly found in their sexual (teleomorphic state); Zygomycetes, Ascomycetes, Basidiomycetes
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What are the "fungi imperfect"?
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they are invariably found in their asexual (anamorphic) state; Deuteromycetes
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Fungi can be: ____________, __________, or mutualistic.
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Saprophytic, Parasitic, or Mutualistic
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Saprophytic fungi
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wide spread in environment
involved in decomposing organic matter sporadically cause opportunistic infections |
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Parasitic fungi
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Ringworm --- dermatophytes
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Mutualistic Fungi
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obligatory associations with other microorganisms so non-pathogenic
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Spores are reproductive cells that can be ____________ or ___________ in origin. They are formed: ________________, _____________, ______________.
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sexual (meiotic) or asexual (mitotic)
formed: directly on hyphae, inside sporangia, fruiting bodies |
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Appearance and biological behavior are dependent on ___________.
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temperature
--yeast usu. spherule at body temp ---Mycelial or hyphal at a lower temp. (room or outside temp) ---yeast or spherules can be identified in body tissues |
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why does fungal infection occur?
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bad luck
altered physical barriers compromised host immunity adapted fungi (virulence factors) many infective organisms |
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What are the appropriate clinical signs that you may expect to see with fungal disease?
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respiratory: coughing, sneezing, dyspnea, nasal discharge
dermatologic: alopecia, pruritis, nodules organomegaly or lymphadenopathy |
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What type of exposure history would you expect for a possible fungal disease?
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ask: about travel history
know: which if any fungal agents are endemic |
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What other signs would you expect with a fungal infection?
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lack of response to standard therapies
inflammatory cell types present (cytology or histology) |
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Cell types seen with inflammation
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epithelioid macrophages, multinucleated giant cells
neutrophils (pyo) lymphoid cells plasma cells |
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Systemic fungal disease can be delineated by the interaction of what 2 factors?
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1) inherent virulence of the fungus
2) immune competency of the host |
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True pathogens (diseases)
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Histoplasmosis
Blastomycosis Coccidiomycosis Paracoccidioidomycosis |
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Opportunistic Pathogens (disese)
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Aspergillus
Candidiasis Zygomycosis Cryptococcus Pneumocystis |
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Prognosis of true pathogens (in systemic mycoses)
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subclinical to severe/fatal ---alters immunity or can bypass normal host defenses
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What causes Blastomycosis?
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Blastomyces dermatitidis
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What species can get Blastomycosis?
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Dogs!!!!
Cats (especially large breed or young dogs) |
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What is the morphology of Blastomyces dermatitidis?
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2x size of a neutrophil
deep blue broad budding extracellular lots of neutrophils around |
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What is the distribution of Blastomyces dermatitidis?
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Soil!!! of the SE and South central states (including SE VA)
Yeast phase in body hyphal phase in culture |
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What are the signs of Blastomyces dermatitidis?
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Respiratory (dyspnea, Exercise Intolerance, cough), anorexia, weight loss, skin lesions, fever, lymphadenopathy, uveitis, anemia. Bone involved in radiographs
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How do you diagnose Blastomycosis?
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direct visualizaion in aspirations of LN, spleen, necropsy tissue, AG detection much better than AB detection
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What are some predisposing factors for Blastomycosis?
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From living by body of water near sea level.
dogs more prone than humans. Recent rains or moist kennels (w/soil) in shady areas (BAD) |
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Remember the B's for Blastomycosis
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Blasto: Basophilic, broad-based-budding
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Blastomycosis treatment
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itraconazole, amphotericin B (nephrotoxic)
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Blastomycosis prognosis
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variable - good to guarded (severity of lung involvement and CNS involvement poor prognostic indicators)
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What species are infected by Histoplasma capsulatam
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dogs
cats |
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Morphology of Histoplasma capsulatam
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intra or extracellular
Half-empty/half-full (baso and eosino centers) clear false capsule |
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Distribution of Histoplasma capsulatam
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Bird/Bat droppings - nitrogen rich soil
river valleys of midwest, SE US, yeast phase in body, hyphal phase in culture |
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Signs of Histoplasma capsulatam infections
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Cats: nonspecific disseminated dz
Dogs: anorexia, fever, resp signs, GI involvement, often anemic with low liver values diffuse interstitial to miliary pattern on rads |
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How do you diagnose Histoplasma capsulatam infection?
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cytology or histopathology of BONE MARROW, LN, fluids, tissue, blood, rectal scrape
immuno tests cross react w/ blasto -UNRELIABLE |
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Treatment of Histoplasma capsulatam infections
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itraconazole is preferred drug of choice
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Predisposing factors/Prevention of Histoplasmosis
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stand downwind of dropping piles, building demolitions
beware of INHALATION |
