Mycology TD
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| show | Through isolation and identification techniques the causative organism can be determined.
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| There are four classes of fungi responsible for human infections. These classes are based on sexual cycles which are usually not seen in cultures of clinical materials. | show 🗑
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| Safety in the clinical laboratory is important. Molds by their nature can easily become airborne and infect laboratory personnel. | show 🗑
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| show | The cabinet should be located in a quiet area to minimize disruption of the air flow into the cabinet.
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| India ink is a suspension of carbon particles in a solution of glycerol and water. When combined with pelleted material from cerebrospinal fluid, India ink allows visualization of the polysaccharide capsules of the yeast, Cryptococcus neoformans. | show 🗑
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| show | Once the two drops meet the coverslip is pushed away. The coverslip is then allowed to settle onto slide. This technique will provide areas of varying ink densities which enhance the visibility of encapsulated yeast. Examine at 400X magnification.
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| A 10% potassium hydroxide (KOH) preparation is used when specimens such as hair, nails, skin or tissue are to be examined for fungal elements. KOH digests the host cellular material allowing the fungal elements to be more easily seen | show 🗑
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| show | Allow preparation to remain at room temperature for 5-20 minutes. Examine under the microscope at 400X magnification.
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| For a more sensitive direct exam of clinical material, calcofluor white can be added to the traditional 10% KOH preparation. Calcofluor binds to the chitin in fungal cell walls. The bound compound fluoresces when exposed to UV light. | show 🗑
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| show | The intensity of staining of fungi may vary from negligible to strongly gram-positive.
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| The Gram-Weigert stain is used to detect Pneumocystis carinii. The Gram-Weigert stain is used to detect Pneumocystis carinii. | show 🗑
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| Histologic stains are useful to demonstrate fungal elements in host tissue. | show 🗑
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| A variety of specific fungal media have been developed 2 isol. & grow yeast & molds. Choice of culture media 2 be used is dependent upon type of clinical specimens, patient history & organisms 2 be isolated. Further considerations are the mycologist's e | show 🗑
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| show | Brain heart infusion agar with sheep blood is used as an enriched medium to isolate the the more fastidous fungi.
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| Most yeasts form visible colonies within 2-3 days. Yeast colonies vary in color, shape, and texture. | show 🗑
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| show | Done
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| show | Smooth convex surfaces are common, but some species have colonies with folded surfaces.
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| show | Done
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| show | Differential agars can be used as primary isolation media or as subculture media to separate similar looking yeast by color.
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| The wet mount is used to determine if a colony is yeast or bacteria. | show 🗑
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| show | Mix colony in water to produce a light suspension. Place coverslip on drop. Examine under the microscope at 400X magnification
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| The germ tube test is a rapid method to distinguish Candida albicans from other yeast. | show 🗑
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| Make a light suspension of the unknown yeast in calf serum. Incubate at 35ºC for 2-3 hours. | show 🗑
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| For identification of Candida albicans, it is important to distinguish germ tubes from pseudohyphae. | show 🗑
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| Yeast morphology agar, such as cornmeal agar with Tween 80, can be used to demonstrate pseudohyphae, true hyphae, budding cells and chlamydoconidia | show 🗑
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| Using an inoculating needle or loop, make 3 or 4 streaks of the yeast on the surface of the cornmeal agar. Make 3 or 4 streaks of yeast on surface of cornmeal agar. | show 🗑
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| show | Demonstration of ascospores is helpful in identifying these yeast. On routine Kinyoun acid-fast stain, ascospores stain red and vegetative cells stain blue.
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| Assimilation tests are used to determine the ability of a yeast to use a carbon or nitrogen source for growth. | show 🗑
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| show | Done
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| Enzymatic tests are used to detect the presence of enzymes that degradate specific substrates. | show 🗑
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| Often it is necessary to supplement routine indentification tests. | show 🗑
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| show | Aerial hyphae grow above the surface of the agar and give texture to the colony. Vegetative hyphae grow into the agar like roots.
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| show | Within the mold group, growth rates can also vary greatly from appearing in 2-3 days to 2-3 weeks.
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| show | The aerial hyphae (obverse) may have a different color than the vegetative hyphae (reverse). Diffusible pigments may also be present.
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| The texture of the colony is helpful in identifying molds. The height of the aerial hyphae growing above the surface of the agar gives texture to the colony. | show 🗑
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| Differential tests aid in the identification of molds. The presence or absence of growth on differential media or color change due to pH may suggest specific species. ie, bromcresol purple-milk solids-glucose (BCP-MSG) agar | show 🗑
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| Various techniques and stains are used to visualize the microscopic features of molds grown on culture media. | show 🗑
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| show | Two commonly used stains are lactophenol cotton blue and lactofuchsin.
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| show | Begin by placing a drop of stain on a glass slide.
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| show | Aerial and vegetative hyphae should be included, avoiding white sterile hyphae on the periphery
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| Transfer sample to the stain. | show 🗑
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| Add a coverslip to the teased sample, pressing down on the coverslip, if necessary, to flatten sample and evenly disperse stain under coverslip. | show 🗑
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| show | Begin by placing a drop of stain onto a clean microscope slide.
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| show | Add another drop of stain on top of the tape. Cover drop with coverslip. Examine slide at 200 - 400X magnification.
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| show | Begin by using bent wire hook to pick up a portion of the colony. Innoculate the agar surface in straight line. Multiple inoculation sites can be made on the same plate. This will allow a culture to be examined over a period of weeks as culture matures.
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| At the site of the inoculated line, place a flamed coverslip at an acute angle into the agar surface. When the growth appears mature, pull one of the coverslips from the agar. Place the coverslip onto a drop of stain on a microscope slide. | show 🗑
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| show | The presence of cone-shaped perforations on the hair shaft is a positive test. The absence of perforations after 4 weeks of incubation is considered a negative test.
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| Once the microscopic preparations are made and stained, it is necessary to examine them for the unique morphologic features that define different molds. | show 🗑
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| Conidia are asexually produced cells that disperse and give rise to new fungal colonies. | show 🗑
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| Blastoconidia are formed by budding. Buds are produced by de novo growth from the mother cell. This is the manner in which most yeast cells reproduce. | show 🗑
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| show | The ring-like scars are useful morphological features which help to distinguish molds that produce annelloconidia from other molds
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| show | Poroconidia are produced through a pre-existing pore on the mother cell.
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| Aleurioconidia are formed from a newly formed hyphal branch which then separates from the main hypha by formation of a cross wall. | show 🗑
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| Arthrocondia are formed by structural changes in the cell walls and septa of preformed hyphae. They are produced along the entire length of the hypha. In some species, the arthroconidia are separated from one another by empty cells. | show 🗑
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| show | Sporangiospores are formed only by members of the fungal Class known as Zygomycetes (e.g. Rhizopus and Mucor)
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| Tinea versicolor is characterized by altered coloration of the stratum corneum due to overgrowth of Malassezia furfur, a skin commensal. Involved areas may be lighter or darker than surrounding skin. | show 🗑
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| Skin scrapings directly examined microscopically can be diagnostic for tinea versicolor. Hyphal and yeast-like forms can be seen in a "spaghetti and meatball" configuration | show 🗑
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| The cells of Malassezia furfur are yeast-like and give the appearance of budding. However, the mother cells are actually phialides. | show 🗑
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| Tinea nigra is characterized by darkly pigmented non-inflammed lesions in the surface of the skin. It is caused by Phaeoannellomyces (Exophiala) werneckii, a darkly pigmented (dematiaceous) mold. | show 🗑
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| Phaeoannellomyces werneckii produces a beige yeast-like colony which matures into a black velvet-napped mold with a black reverse. | show 🗑
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| show | The dark yeast-like single and doubled-celled conidia are known to be annellides. Striations which are scars left from previous budding may be seen at the elongated end of the cells.
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| show | It is caused by Trichosporon beigelii, a yeast-like mold.
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| While technically a mold, Trichosporon beigelii gives the initial appearance of a yeast. Mature colonies are yellowish white with a suede-like texture. | show 🗑
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| show | Done
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| The dermatophytes are a group of molds that infect the skin, hair and nails. The three genera classified as dermatophytes are: Epidermophyton, Microsporum and Trichophyton. Ringworm is a common term for dermatophytosis due to the circular skin lesion. | show 🗑
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| show | All genera of dermatophytes have the same morphology on direct examination.
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| show | The obverse of the colony can vary from brownish-yellow to olive gray. The reverse is orange to brown
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| show | Microconidia are not produced.
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| Microsporum canis causes skin and hair infections. The obverse color of the colony is white with a yellow fringe. | show 🗑
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| show | A few club-shaped microcondidia may be present.
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| Trichophyton mentagrophytes may infect any body surface. It most frequently causes athlete's foot. | show 🗑
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| A microscopic preparation of a T. mentagrophytes colony will demonstrate round, clustered microconidia. | show 🗑
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| T. rubrum sometimes resembles T. mentagrophytes. Differential tests may be used to distinguish between these two species. | show 🗑
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| T. mentagrophytes: hair perforation = positive urea = positive BCP-MSG = profuse growth with alkalinization. | show 🗑
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| Trichophyton rubrum infects nails and the skin of hands, feet, and torso. It rarely infects hair. The obverse appearance is typically white and downy. | show 🗑
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| show | Differential tests may be necessary to distinguish Trichophyton rubrum from Trichophyton mentagrophytes.
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| show | T. mentagrophytes: hair perforation = positive urea = positive BCP-MSG = profuse growth with alkalinization.
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| Tricophyton tonsurans commonly causes ringworm of the scalp. It may also infect skin and nails. The obverse appearance is variable. It may be white, gray, yellow, tan or brown. The texture may be powdery to suede-like. | show 🗑
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| show | ---->
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| Nutritional requirement tests using Trichophyton agars can be used to separate T. tonsurans from other Trichophyton species. | show 🗑
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| Sporotrichosis follows a penetrating wound which inoculates the subcutaneous tissue with a soil mold, Sporothrix schenckii. In developed countries, the typical history involves a deep puncture from a rose thorn. | show 🗑
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| Sporothrix schenckii is a thermally dimorphic mold. When cultured at 25-30ºC, it appears as a cream-colored, moist colony which turns brown to black . Short aerial hyphae are usually produced in subculture. | show 🗑
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| show | A second type of conidium is produced along the sides of the hyphae. The conidia turn dark with age. At 35-37ºC, round, oval or elongated budding yeast cells are seen.
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| Chromoblastomycosis is a chronic disease that follows inoculation of soil molds into subcutaneous tissue. Typical lesions are large warty growths frequently described as cauliflower lesions. 4 orgs cause chromoblastomycosis: | show 🗑
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| Colonies of Cladophialophora carrionii grow slowly and tolerate temperatures up to 37º C. | show 🗑
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| show | Dark scars on the conidia are typical at the points of attachment.
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| show | The obverse appearance is dark green to brown with velvety texture. The reverse is black
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| show | Fonsecaea are dematiaceous molds that may produce four types of conidiation. Rhinocladiella type: oval conidia are borne on swollen denticles at the tip and along the sides of the conidiophore.
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| Fonsecaea are dematiaceous molds that may produce four types of conidiation. Cladosporium type: conidiophores produce shield-shaped conidia that bear oval conidia in branching short chains. The conidia have scars of attachment. | show 🗑
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| Phialophora verrucosa is a slow-growing dematiaceous mold. | show 🗑
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| show | A distinct cup-like collarette forms at the tip of the phialide. Round to oval conidia typically cluster at the tip of the phialide.
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| show | -> including filamentous gram-positive bacteria and molds which are introduced into tissue via a puncture wound. From primary subcutaneous lesions, mycetomas errode into contiguous tissues including muscle and bone.
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| show | The obverse appearance is white and cottony, becoming gray with age. The reverse is tan with darkening areas.
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| show | Cleistothecia are large brown structures containing oval ascospores, which are released when the cleistothecia bursts. The asexual form, Scedosporium apiospermum, has oval conidia on long slender conidiophores.
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| Colonies of Exophilala jeanselmei are slow growing with a dark olive to black yeast-like appearance | show 🗑
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| Exophiala jeanselmei produce profuse oval conidia | show 🗑
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| show | Nocardia spp. are weakly acid-fast and may appear beaded on stained preparations. In long-standing infections the organism exists in granules, which should be crushed and examined microscopically.
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| show | Wangiella dermatitidis, Cladophialophora (Xylohypha) bantiana, Exophiala spp., and Phialophora spp. Phaeohyphomycosis can vary in severity depending on their location and size.
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| Colonies of Wangiella dermatitidis are slow growing. | show 🗑
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| Wangiella dermatitidis produces profuse conidia | show 🗑
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| show | Colonies are olive to gray-black with a velvety texture. The reverse is black.
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| show | The conidiophores produce long chains of oval conidia.
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| Colonies of Exophiala spp. are slow growing with a dark olive to black yeast-like appearance. | show 🗑
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| Exophiala spp. produce profuse oval conidia. | show 🗑
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| show | The obverse appearance is dark gray-green, brown or black and velvety to wooly. The reverse is black.
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| show | A saucer-like collarette forms at the tip of the phialide. Round to oval conidia typically cluster at the tip of the phialide.
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| show | / common in immunocompromised patients. The CNS most frequent site of dissemination. Skin and viscera are also involved in a small % of patients. Cryptococcus neoformans -> w/w distribution (pigeon droppings)
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| The India ink preparation is the traditional method used to look for Cyptococcus neoformans in cerebrospinal fluid. The yeast's capsule creates a halo around the cell. | show 🗑
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| show | Cryptococcus neoformans may be visible on direct Gram stain of cerebrospinal fluid. The yeast cells may vary in size.
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| show | Most patients with blastomycosis have self-limiting pulmonary infections. Most cases present with cutaneous lesions reflecting hematogenous dissemination. Other less common sites of dissemination include viscera, bone, and the prostate gland.
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| The yeast cells of Blastomyces divide with a characteristic broad-based bud. These can be seen on direct examination of clinical specimens. | show 🗑
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| show | cream colored and irreg shaped. Conversion of the mold to the yeast phase (or yeast to mold imp for ID of Blastomyces. DNA probe is commercially available for confirmation. Oval to round conidia form at the end of short conidiophores. yeast form at 37ºC.
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| Coccidioidomycosis found primarily in the west hemis with endemic areas in semi-arid regions:southwestern US South America. Caused by Coccidioides immitis, a dimorphic fungus, that appears as spherules in host tissue and as a mold in the env. | show 🗑
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| Histologic preparations of host tissue reveal the presence of the spherule form of Coccidiodes immitis. These spherules contain endospores. Coccidioides immitis is a mod rapid-growing dimorphic mold. | show 🗑
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| show | The arthrocondia of Coccidioides are readily airborne and pose a serious hazard to laboratory personnel. Therefore, it is recommended that all molds be handled in a biosafety cabinet.
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| With age, the hyphae of Coccidioides begin to form arthroconidia | show 🗑
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| show | Histoplasmosis is distributed worldwide. The endemic areas in the United States include the Ohio-Mississippi valleys where the organism is found in soil enriched with bird or bat droppings
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| Histoplasmosis originates as an asymptomatic or self-limiting, mild pulmonary infection. A small percentage of patients develop chronic pulmonary lesions. | show 🗑
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| show | The yeast colonies are cream-colored and may be glabrous. Conversion of the mold to the yeast phase (or yeast to mold) is important for identification of Histoplasma. A DNA probe is available to distinguish Histoplasma from other white fluffy molds
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| The mold form of Histoplasma capsulatum produces round, warty (tuberculate) macroconidia. Microconidia may also be present | show 🗑
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| Paracoccidioidomycosis is caused by Paracoccidioides brasiliensis, a thermally dimorphic fungus, that appears as large, multiply budding yeasts in host tissue and as a mold in the environment. | show 🗑
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| show | Yeast colonies are white and creamy. Conversion of the mold to the yeast phase (or yeast to mold) is important for ID of Paracoccidioides.
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| Mold form of Paracoccidiodes brasiliensis doesnt usually produce distinctive structures. Chlamydoconidia, arthroconidia, and microconidia may be present | show 🗑
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| show | When a patient is immuno-compromised due to high dose steroids, neutropenia, HIV, or organ transplants, opportunistic fungi may cause severe infection.
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| show | Gram-positive budding yeast cells and pseudohyphae may be seen on direct Gram stains of clinical material
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| Candida albicans produces blastoconidia (budding yeast) in culture. | show 🗑
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| The conidial heads (the reproductive structure) of Aspergillus fumigatus is composed of several parts. The bulb is known as the vesicle. From the vesicle grow phialides and the phialides produce chains of round conidia. | show 🗑
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| There are many species in the Aspergillus group. Description of the phialides and their growth pattern is important to differentiate one species from another. | show 🗑
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| The conidial heads of Aspergillus flavus are radial. The phialides can be uniserate or biserate and produce chains of round conidia. | show 🗑
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| Rhizopus spp. is a very rapidly growing cottony mold. The obverse of the colony is light gray-brown. The reverse is pale | show 🗑
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| show | Mucor spp. is a very rapidly growing mold. The obverse is white becoming gray with age and has a cottony texture. The reverse is white.
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| show | done
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| show | staining lung tissue or secretions with the Gram-Weigert stain and/or histologic stains. P. carinii cysts stain blue with Gram-Weigert and are round to oval in shape. Some cysts will stain faint or even appear to be refractile.
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| show | Acremonium have long slender phialides that produce oval, unicellular microconidia that cluster at the tip of the phialide.
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| The clusters of microconidia are easily disrupted from the tip of the phialide | show 🗑
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| show | Alternaria produces dematiaceous (dark), poroconidia with transverse and longitudinal septa (muriform).
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| show | Chrysosporium is a large, diverse group which produce aleurioconidia that are usually unicellular and form at the ends of short conidiophores, intercalary, or directly from the hyphae
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| show | Chaetomium produces a fruiting body called an ascocarp which is covered with hair-like protrusions (setae) and contains large numbers of oval ascospores.
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| Curvularia is a rapidly growing mold. The obverse is white which darkens with age and has a wooly texture. The reverse is dark brown. | show 🗑
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| The multicellular poroconidia of Curvularia are curved due to the swelling of the central cell. | show 🗑
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| show | Fusarium is a rapidly growing mold. The obverse is white to pale yellow or pink, and occasionally lavendar with cottony texture. The reverse varies from pale to red to violet or brown.
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| show | The microconidia vary from oval to cylindrical in shape, may be uni- or multicelluar, and cluster at the ends of slender phialides. The microconidia of Fusarium may be confused with the microconidia of Acremonium.
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| Paecilomyces is a rapidly growing mold. The obverse is white to beige or lavendar and darkens with age and has a powdery or cottony texture. The reverse is colorless to pale brown or yellow. | show 🗑
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| show | Penicillium is a rapidly growing mold. The obverse is blue-green with a white border and a velvety texture. The reverse is pale or light yellow.
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| show | Penicillium differs from Paecilomyces by its thick, flask-shaped, tightlly clustered phialides.
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| Phoma is a rapidly growing mold. The obverse is light to olive gray with a velvety texture. The reverse is pale yellow to dark brown. | show 🗑
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| Pithomyces is a very rapidly growing mold. The obverse is pale gray to brown with a wooly texture. The reverse is dark brown to black. | show 🗑
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| Scopulariopsis is a moderately rapid growing mold. The obverse is white to light brown with velvety texture. The reverse is light yellow to brown. | show 🗑
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| show | Ulocladium produces dark, rough-walled, muriform poroconidia.
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| The poroconidia of Ulocladium arise from geniculate (bent) conidiophores | show 🗑
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