Practical 1 – Flashcards
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| Which yeast are germ tube positive? |
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| C. albicans and C. dublinenses |
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| Which yeast is germ tube negative? |
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| C. glabrata |
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| Which yeast is India Ink positive? |
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| C. neoformans |
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| What makes C. albicans/dublinenses germ tube positive? |
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| psuedohyphae |
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| What makes C. neoformans India Ink positive? |
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| Capsule/Halo |
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| What differentiates Epidermophyton from the other dermatophytes? |
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| Epidermophyton has thin and smooth macrocondidia growing directly from septate hyphae |
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| What differentiates Microsporom from the other dermatophytes? |
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| Microsporum has rough and turbulent macrocondidias with a spindle shape, growing from multiseptate hyphae |
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| What differentiates Trichophyton from the other dermatophytes? |
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| Trichtophyton have microcondidia growing directly from the hyphae |
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| What differentiates Penicillium from Aspergillus? |
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| Penicillium has a condidiaphore which gives rise to thin finger-like phialides |
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| What differentiates Aspergillus from Penicillium? |
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| Aspergillus has condidiaphores which give tise to a vesicle which has phialides on top of it |
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| What are the names of the three dimorphic fungi? |
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| Blastomyces dermatitdis, Coccoidiodes immitis, and Sporothrix schenkeii |
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| What makes the yeast form of Blastomyces dermatitdis special? |
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| grows at 37 C, large, broad-based, unipolar yeast-like cell |
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| What makes the yeast form of Coccoidiodes immitis special? |
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| grows at 37 C, large, thick, contains endospores |
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| What makes the yeast form of Sporothrix schenkeii special? |
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| grows at 37 C, oval to cigar shaped yeast cells, single-multiple buds from one cell |
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| What makes the mold form of Blastomyces dermatitdis special? |
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| grows at 25 C, septate hyaline hyphae, unbranched, short condidiophores at right angles |
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| What makes the mold form of Coccoidiodes immitis special? |
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| grows at 25 C, barrel-like anterospores with thin septate hyphae |
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| What makes the mold form of Sporothrix schenkeii special? |
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| grows at 25 C, septate hyaline hyphae, condidiophores and conidia, looks like roses growing off the hyphae |
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| Name the dematiacious molds |
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| Alternaria spp. and Curvularia spp. |
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| What differentiates Alternaria spp. from Culvularia spp.? |
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| Alternaria spp. appears with transverse and longitidinal sepations in the condidia |
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| What differentiates Culvularia spp. from Alternaria spp.? |
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| Culvularia spp. appears with curved macrocondidia |
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| What color is a positive modified kinyoun stain? |
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| Red |
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| What color is a positive kinyoun stain? |
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| Red |
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| What color is a positive fluorescent stain? |
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| Gold |
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| What color is a negative modified kinyoun stain? |
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| blue/green |
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| What color is a negative kinyoun stain? |
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| blue/green |
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| What color is a negative fluorescent stain? |
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| black |
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| Why do we use Kinyoun stains? |
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| Kinyoun stains are used for bacteria which do not take up the Crystal Violet stain well |
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| Why do we use modified kinyoun stains? |
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| some bacteria do not take up the crystal violet well, and do not have enough mycolic acid in their walls to hold the primary stain during decolorization, the decolorizer in modified kinyoun is less potent |
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| How do you do a modified kinyoun? |
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3 minutes with carbol fuchsin rinse decolorize with 1% sulfuric acid rinse Counter stain for 30 seconds with methylene blue, malachite green or brilliant green rinse air dry |
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| Describe Actinomyces |
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| endogenous strain, obligate anaerobe, causes lumpy jaw and IUD infections, sulfur granules present in tissue, molar tooth colony, modified kinyoun negative |
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| Describe Nocardia |
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| obligate aerobe, causes pulmonary and skin/tissue infections (mycetomas), colonies appear white, tan, orange, dry, wrinkled, and chalky, modified kinyoun positive |
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| Describe Streptomyces |
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| causes skin infections (mycetomas) and pulmonary diseases, colonies appear waxy, modified kinyoun negative |
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| How do you do a kinyoun stain? |
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| 5 minutes with carbol fuchsin rinse with tap water 2 minutes with 3% decolorizer rinse 1-3 minutes with methylene blue rinse air dry |
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| How do you do a fluorescent stain? |
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| 15-20 minutes with auramine-rhodamine stain rinse 2-3 minutes with 3% HCl decolorizer rinse 2-4 minutes with potassium permanganate rinse air dry |
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| Describe mycobacterium tuberculosis |
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| slow grower, nonpigmented, tan, buff, dry and rough on plate, cord formation on stained smear, niacin positive, fluorescent and kinyoun positive |
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| Which mycobacterium are photochromagens |
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| M. kansasii and M. marinum |
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| When does a photochromagen produce pigment? |
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| upon exposure to light |
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| Which mycobacterium are scotochromagens? |
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| M. gordonate |
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| When does a scotochromagen produce pigment? |
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| always |
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| Describe M. fortuitum |
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| rapid grower, buff, moist colonies |
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| Describe M. avium-intracellulare |
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| rapid grower, nonphotochromagen |
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| describe M. leprae |
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| no growth in routine agar, found on foot pads of armadillos |
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| Which other organisms can positive false positives in AFB cultures? |
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| bacteria, nocardia, and yeast |
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| What is the general description of mycobacterium? |
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| pleomorphic beaded gram positive rods, non motile, non branching, non spore forming, strict aerobes, varying growth rate, environmental contaminants (except MTB) |
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| What are the staining methods for AFB? |
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| Ziehl Nelson, Kinyoun, and Fluorescent |
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| What is different between the light microscope and the fluorescent microscope? |
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| Light source comes from above (fluorescent) and below in the light. The fluorescent light hits the molecules and excites them which causes them to give off light as they come back down to ground state |
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| What media is mycobacterium cultured on? |
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| Lowenstein Jensen agar |
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| What precautions should you take when working with AFB? |
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| Negative pressure room, biological safety cabinet and face mask, saftey cups for centrifugation, splash-proof discard containers, disposable inoculating needles, disposal of waste |
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| What are acceptable specimens for AFB culturing? |
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| respiratory specimens (3 days worth), urine (centrifuge before processing), stools (direct smear screen), bone and tissue (ground up), blood and fluid (mycolyic bottle or isolator tube) |
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| What do you use to decontaminate AFB specimens? |
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| 1:1 ratio of specimen to NALC with NaOH |
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| Describe the steps in processing AFB specimens? |
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| add NALC and NaOH Vortex, let sit for 20 min add phosphate buffer concentrate with centrifugation for 15 min pour off supernatent inoculate media, make 2 smears, heat fix to slide |
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| Describe LJ agar |
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| egg based |
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| Describe Middlebrook agar? |
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| agar or broth based |
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| In which environment do you incubate LJ slants? |
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| dark, Co2 |
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| 4 ways of identifying mycobacteria |
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| runyoun classification (growth rate), chromagen (pigment), biochemical testing, or DNA probes/PCR |
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| How does Mass Spectrophotmetrey identify mycobacteria? |
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| analysis of proteolytic peptides |
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| How does HPLC identidy mycobacteria? |
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| quantification of mycolic acids |
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| What are the 5 primary anti-TB drugs? |
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| Isoniazid, Rifampin, Ethambutol, Streptomycin, and Pyrazinamide |
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| What are the 3 methods of susceptiblity testing for multi-drug resistant TB |
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| agar with antibiotics, broth dilution (MIC) and PCR |
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| What is the general description of Actinomycetes? |
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| beaded, branching, filamentous, gram positive rods |
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| 5 ways to identify actinomycetes |
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| gram positive rod, branched filaments, grows on BAP, CAP, LJ and SAB (3-6 days), decomposition of casein and DNA sequencing |
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| Yeast on a gram stain are |
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| gram positive |
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| What is KOH prep used for? |
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| breaks down keratin and releases it into solution |
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| How do you identify C. neoformans? |
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| india ink positive, urease positive on urea slant or rapid latex antigen test on CSF or serum |
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| What are mycelum? |
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| long structures, intertwined on SAB agar, characteristic of fungal cultures |
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| How do you identify C. glabrata? |
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| RAT test positive (rapid assimilation trehelose) |
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| How do you identify yeast? |
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| Rapid ID or automated ID based on sugar assimilation |
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| How do you identify mold? |
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| Structures and touch prep |
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| What is in touch prep? |
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| lactophenol cotton blue stain |
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| how do perform a slide culture? |
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| Take a circle of sab dex agar set on glass side in petri dish (with toothpicks and moist towel) inoculate agar with mold via notches on side corners place cover slip on top incubate remove cover slip, stain and look for structures |
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| What is PNA fish? |
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| peptide nucleic acid FISH, tag and attach probe to molecular structure |
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| What is unique about the structure of C. albicans? |
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| chlamydospores and psuedohyphae |
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| How do you differentiate between Geotrichum spp. and trichosporon spp? |
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| Geotrichum shows individual artherospores with septate hyphae, Trichosporon shows blastocondidia |
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| What are the three Zygomycetes? |
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| Rhizopus, Mucor and Absidia |
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| What is characteristic of Rhizopus? |
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| rhizoids at the bottom of sporeangiophores |
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| What is characteristic of Mucor? |
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| no rhizoids |
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| What is characteristic of Absidia? |
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| Rhizoids in between sporeangiophores |
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| [image] |
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| Cryptococcus neoformans, india ink |
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| [image] |
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| C. albicans, wet mount |
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| [image] |
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| Geotrichum spp. Touch Prep |
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| [image] |
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| Trichosporon sp. Touch prep |
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| [image] |
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| Alternaria sp. |
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| [image] |
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| Curvularia sp. |
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| [image] |
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| Aspergillus sp. |
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| [image] |
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| Penicillium sp. |
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| [image] |
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| Epidermophyton |
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| [image] |
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| Microsporum sp. |
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| [image] |
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| Trichophyton sp. |
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| [image] |
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| Trichophyton sp. |
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| [image] |
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| Blastomyces dermatitidis, yeast |
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| [image] |
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| Blastomyces dermatitidis, mold |
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| [image] |
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| Sporothrix schenkeii - mold |
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| [image] |
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| Rhizopus |
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| [image] |
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| Absidia |
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| [image] |
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| Mucor |
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| [image] |
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| Aspergillus |
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| [image] |
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| C. Albicans |
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| [image] |
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| Penicillium |
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| [image] |
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| Aspergillus |
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| [image] |
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| Rhizopus |
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| [image] |
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| Germ Tube Negative |
