Microbiology Exam: Mycology

  1. What are fungi?
    • Eukaryotic
    • Lack chlorophyll
    • Reproduce by spores
    • Filamentous or unicellular
    • Macroscopic or microscopic
    • Few species cause human disease
    • Many live as saprobes
    • Humans usually accidental hosts
    • Lack of susceptibility to antibiotics
  2. Yeasts- Unicellular Fungi Colonies
    • Moist
    • Creamy
    • Pasty
  3. Molds-Filamentous Fungi
    • Fluffy
    • Cottony
    • Woolly
    • Powdery
  4. Dimorphic Fungi
    Can exhibit two forms
    • Thermally dimorphic so temperature dependent
    • 25-30 C = mold
    • 35-37 C = yeast
  5. Yeasts- General Descriptions
    • Unicellular
    • -Round to oval
    • -Some have capsules
    • Reproduction
    • -Asexually by budding-blastoconidia formation
    • -Sexually by ascospores or basidiospores
    • Pseudohyphae
    • -Elongated buds connected to one another
    • -Not all species produce pseudohyphae
  6. Yeasts- Candida albicans
    • Part of our normal flora
    • Superficial infections
    • Invasive infectionsImage Upload 1
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    • Yeasts- Candida albicans
    • Colony morphology
  8. Image Upload 3
    • Yeasts- Candida albicans
    • -Germ tube production
  9. Image Upload 4Image Upload 5
    • Yeast- Candida albicans
    • -Cornmeal morphology
  10. Yeasts- Other Candida species
    • C. tropicalis
    • C. krusei/inconspicua
    • C. parapsilosis
    • C. glabrata
  11. -Exists in nature
    -Causes disseminated disease
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    • Yeasts-Cryptococcus neoformans
    • -Exists in nature
    • -Causes disseminated disease
  12. Colony Morphology
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    Yeasts- C neoformans
  13. India Ink
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    Yeasts- C neoformans
  14. Latex agglutination
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    Yeasts- C neoformans
  15. Cornmeal morphology
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    Yeasts- C neoformans
  16. Bird seed agar
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    • Yeasts- C neoformans
    • -Phenol oxidase detection
  17. Other Cryptococcus species
    • Urease positive
    • Inositol assimilation positive
    • Round yeast cells only on cornmeal agar
  18. Causes disease in immunocompromised
    Can colonize healthy individuals
    Urease positive
    Yeasts- Trichosporon beigelii
  19. Colony morphology
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    Yeasts- T beigelii
  20. Cornmeal morphology
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    Yeasts- T beigelii
  21. Causes White Piedra
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    Yeast- T beigelii
  22. Causes Tinea versicolor-
    (pityriasis versicolor)
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    Yeasts- Malasezzia furfur
  23. Part of normal human flora
    Can cause disseminated infection
    Microscopic exam
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    Yeasts- M furfur
  24. Special growth requirements- lipophilic
        so needs lipids or fatty
        acids to grow in vitro
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    Yeasts- M furfur
  25. Other yeasts
    Base identification on morphologic and biochemical criteria
    • Morphology determined on cornmeal agar
    • Biochemical reactions- API’s or Vitek
  26. Aseptate (nonseptate)
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    Molds- hyphae
  27. a.Image Upload 21
    b.Image Upload 22
    • Molds- hyphal pigmentation
    • a. Dematiaceous
    • b. Hyaline
  28. Have many different arrangements and sizes
    Helps to identify the mold
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    Molds- spores
  29. Molds- Traditional Taxonomy
    -4 Phyla
    • Zygomycota
    • Ascomycota
    • Basidiomycota
    • Deutromycota
  30. Aseptate hyphae
    Rapid growers
    “lid popper”
    Asexual reproduction
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  32. Septate hyphae
    Asexual reproduction
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  33. Sexual reproduction
    Ascospores within 
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  34. Septate hyphae
    Sexual reproduction –basidiospores
    Plant pathogens or environmental organisms
    Rarely cause human disease
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  35. Contains mushrooms,
         rusts and smuts
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  36. No sexual stage
    Septate hyphae
    Classified based on conidia
    Includes most saprobic and pathogenic fungi
  37. Molds-Practical Classification
    4 Categories
    • Superficial or cutaneous mycoses
    • Subcutaneous mycoses
    • Systemic mycoses
    • Opportunistic mycoses
  38. Infect hair, skin and nails
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    Superficial Mycosis
  39. Confined to subcutaneous layer without spreading to other sites
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    Subcutaneous Mycosis
  40. Contains the dimorphic fungi
    Primarily infects the lungs
    They may disseminate to any organ system
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    Systemic Mycosis
  41. Found primarily in immunocompromised patients
    An ever-expanding list of organisms
    All may cause disseminated disease
    Opportunistic Mycoses
  42. Molds- A systematic approach to identification
    • 1.Look at the hyphae
    • -Aseptate or septate?
    • 2.Look at color of hyphae/spores
    • -Hyaline or dematiaceous?
    • 3. Look at type and arrangement of spores
    • -Single or multi-celled?
    • -Single or in clusters?
    • 4. Growth rate and temperature studies
    • 5. Colony morphology
    • -Color- fromt and reverse
    • -texture
  43. Common Specimen Types
    • Respiratory tract specimens
    • Cerebrospinal fluid
    • Blood
    • Hair, skin and nail scrapings
    • Urine
    • Tissue, bone marrow and sterile body fluids
  44. Recommended Media
    • All media should contain antibacterial agents unless specimen is from a sterile site
    • Sabouraud with gentamicin and chloramphenicol
    • Media with and without cycloheximide
    • Mycosel
    • Sabouraud
    • Use a combination of above mentioned media types based on specimen
  45. Incubation Requirements
    • Preferably 30 C
    • Relative humidity 40-50%
    • Hold 3 days to 6 weeks –depending on specimen type and request
    • Gas permeable tape
    • Examined at least 3 times weekly
  46. Direct Microscopic Exams of Specimens
    -Gram stain

    • -Potassium hydroxide preparations 
    •       (KOH Prep)
    • -Calcofluor White 
    • Fluorescent microscopy
    • -Gomori methenamine silver (GMS)
    • For histologic sections or direct specimens
    • -Modified acid fast- Nocardia and AFB
  47. Laboratory Safety Considerations
    • Molds
    • Laminar flow hood and tape plates
    • Yeasts
    • Can be handled on bench top
  48. Soil organisms and plant saprobes
    More often seen on hands and feet
    Most often seen in rural, tropical, agricultural areas
    More often seen in men (occupational exposure)
    Subcutaneous Mycosis
  49. Three groups of subcutaneous infections
    Chromoblastomycosis- warty lesions

    Mycetoma- mycelial tumor

    Phaeohyphomycosis- pigmented dark hyphae
  50. -At site of trauma a warty, cauliflower-like lesion forms
    -Microscopic- sclerotic bodies (copper pennies) seen in tissue

    -Molds are all dematiaceous and form heaped grey to black colonies
  51. Agents of chromoblastomycosis
    • 1. Cladosporium carrionii
    • Long chains of elliptical conidia on branching conidiophores
    • 2. Phialophora verrucosa
    • Flask-shaped phialides with distinct collarette, conidia in clusters at tip
    • “vase of flowers”
    • 3. Fonsecaea (pedrosa and compacta)
    • Can have four arrangements of conidia
  52. At site of trauma a chronic infection occurs characterized by draining sinus tracts, granules, and tumor-like deformities of subcutaneous tissue
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  53. Bacterial cause- Nocardia, Streptomyces, and Actinomyces

    Long filamentous gram positive rods
    Actinomycotic Mycetoma
  54. Granules are many colors: yellow, white, red or black
    Actinomycotic Mycetoma
  55. Fungal cause
    Pseudoallescheria boydii/Scedosporium apiospermum
    Exophialia jeanselmei
    Madurella mycetomatis
    Eumycotic Mycetoma
  56. Any infection caused by a dematiaceous fungi

    Direct microscopic exam yields dark fungal elements
  57. Exophiala jeanselmei
    Colony –yeastlike at first then wooly
    Microscopic –balls of conidia on conidiophore
    Growth at 37C but not at 40C
    Grows with KNO3 media
  58. Phialophora richardsiae
    Microscopic –phialides with distinct flared saucer-like collarettes
  59. Exophiala (Wangiella) dermatitidis 
    Colony-yeastlike when young then velvety black
    Microscopic-ball of conidia appear to slide down conidiophores
    Will grow at 40C
    Doesn’t use KNO3 media
  60. Dimorphic Mycosis Causes deep seated infections
    • Internal organs
    • Lymph nodes
    • Bone
    • Subcutaneous tissue and skin
  61. Dimorphic Mycosis exist in two forms that are temp dependent
    • Mold form (how it exists in nature)
    • In vitro phase 25-30 C
    • Yeast form (invasive tissue form)
    • In vivo phase 35-37 C
    • Can try to accomplish on enriched media with increased CO2
  62. Dimorphic Mycosis Usually considered slow-growing
    • Requires 7-21 days for growth at 25-30 C
    • Though exceptions do occur
    • i.e. large number of organisms in specimen
  63. What are methods of ID for Dimorphic Mycosis
    • In vitro conversion of mold form to yeast form
    • Can be tedious and C. immitis has none
    • Exo-antigen testing
    • Gel immunodiffusion precipitin test
    • Nucleic acid probes
    • Sensitive, specific and rapid 
    • Very expensive
  64. Sporothrix schenkii
    Source of infection
    • Organism lives on vegetation
    • Inoculation occurs through trauma
    • Occupational hazard
    • Farmers, gardeners, florists and miners
    • “rose gardener’s disease”
    • Possibly pulmonary route also
  65. Sporothrix cont’d
    Primary lesion forms
    Non-healing ulcer
  66. Sporothrix cont’d
    Secondary lesions

    • Nodular lesions
    • Lymphatic channels and nodes
    • Rarely disseminates systemically
  67. Sporothrix
    Direct detection from sample
    • Exudate from lesions
    • Silver stain may show cigar shaped yeast cells
  68. Sporothrix culture from sample
    • Culture –mold phase
    • Leathery ,wrinkled colonies that darken with age
    • Young colonies could be mistaken for yeast
  69. Sporothrix Microscopically
    • – conidia borne in clusters at tips of conidiophore = rosette
    • Leathery ,wrinkled colonies that darken with age
    • Young colonies could be mistaken for yeast
    • As culture ages may see “sleeve arrangement” – single conidia along hyphae
  70. Sporothrix Culture –yeast phase
    • Try to convert at 37C on enriched media
    • Cream colored yeast colony
    • Cigar shaped yeast cells- cigar bodies
  71. What are the Endemic areas for Sporothrix?
    • Found world-wide
    • Outbreaks in gold mines
  72. Where is the source of infection for Histoplasma capsulatum?
    • Organism lives in soil enriched with bird manure or bat feces
    • Acquired via inhalation of conidia
  73. What is the etiology of Histoplasma?
    • Pulmonary lesion- primary infection
    • Chronic pulmonary disease- cavitations
    • Secondary dissemination- lymphatics, organs and skin
  74. Histoplasma Direct detection
    • Respiratory tract specimens
    • Bone marrow, tissue or blood by Giemsa may yield round/oval yeasts within macrophages
    • PCR on tissue
  75. Histoplasma Culture
    • Mold phase –slow growing, usually 2-4 weeks
    • Colony –white fluffy, turns brown with age
    • Microscopic –macroconidia at first round and smooth but become tuberculate
  76. Histoplasma Sepedonium
    saprobic mold that looks similar but grows faster
  77. Histoplasma Culture
    • Yeast phase –difficult to convert, not recommended
    • Microscopic –small yeast cells
  78. Where is Histoplasma Endemic?
    • Worldwide distribution
    • Prevelant in Ohio, Mississippi, and Missouri River Valleys
    • Outbreaks following cleaning of chicken coops, barns, pigeon roosts and spelunking
    • In endemic areas- high percentage of population are skin test positive
  79. How is Blastomyces dermatitidis acquired?
    • Acquired by inhalation of conidia
    • Disease state very similar to Histoplasmosis
    • More common in men associated with outdoor occupation
  80. What is characteristic of a primary Blastomyces infection?
    • respiratory infection
    • Dissemination to bones, soft tissue, and skin
  81. What would you see in a direct detection of Blastomyces using
    large thick walled yeast with single bud connected by broad base to parent cell
  82. Describe Blastomyces culture during mold phase:
    • White, waxy to cottony colony
    • Microscopic –single, round to pyriform conidia on conidiophores = “lollipop”
  83. Describe Blastomyces culture during yeast phase:
    • Waxy, wrinkled colonies
    • Relatively easy to convert
    • Microscopically –large thick-walled yeast with broad base
  84. Blastomyces Endemic areas
    • Seen in Americas and Africa
    • Prevelant in Northern Ohio and Mississippi River Valleys and south eastern United States
    • Diagnosed cases are usually the disseminated ones
    • Mississippi River Valley Disease or Chicago Disease
  85. Coccidioides immitis
    Source of infection
    • Acquired by inhalation of arthroconidia
    • Mold phase grows on vegetation producing airborne arthroconidia
  86. Coccidioides Etiology
    • Primary infection is pulmonary disease (60% of which are asymptomatic and self limiting)
    • Dissemination - <1% develop this in bone, CSF, organs or subcutaneous tissue
  87. Coccidioides Direct detection
    • On sputum, bodyfluids or tissues, non-budding, thick-walled spherule containing endospores
    • Spherules may burst and endospores may be confused with yeast
  88. Coccidioides Culture
    • mold phase
    • Cottony white colony
    • Highly contagious!!!
  89. Coccidioides Culture Microscopically
    • hyphae that form barrel-shaped arthroconidia that alternate with empty spaces
    • No yeast phase in vitro only spherules in tissue or sample
  90. Coccidioides Endemic areas
    • Prevelant in desert southwest United States, especially the San Joaquim Valley
    • “Valley Fever”
    • Outbreaks after windstorms
    • Seen in other parts of the world due to travel- “snow birds”
  91. Paracoccidioides brasiliensis
    • Dimorphic fungi
    • Endemic in South America
    • Diagnostic form –yeast phase known as “Mariners Wheel”
    • Mold phase –similar to Blastomyces
  92. Others possible systemic mycoses
    • Zygomycosis
    • Candidiasis
    • Aspergillosis
    • Cryptococcosis
  93. What is the only genus in family Mycobacteriaceae?
  94. What are the only two species that are contagious in the family Mycobacteriaceae?
    M. tuberculosis and M.leprae
  95. What are the characteristics of Mycobacteriaceae?
    • Obligate aerobes
    • Slightly curved rods
    • Acid-Fast
  96. How many organisms are required for an acid fast smear?
    Requires 5,000-50,000 orgs/ml to show a positive smear
  97. What stains are used on acid fast organisms?
    • Fluorochrome stains
    • Carbol Fuchsin stains
  98. What makes an organism acid fast?
    • Resistant to acid-alcohol decolorization due to Mycolic acids that have a lipid layer surrounding peptidoglycan layer of cell wall
    • Involved in virulence
  99. What is the generation time of mycobacteriacea?
    Very long, 2 to 20 hours.
  100. What is the optimal temperature for AFBs (acid-fast bacilli)?
    • Optimal Temperature for most AFB is 35-37°C
    • Some prefer 30°C
  101. How is non tuberculosis mycobacterium classifeid?
    • Pigment-Runyoun 1959 to classify NTM
    • Nonphotochromogens
    • Photochromogens
    • Scotochromogens
    • Rapid Growers
  102. What is M. tuberculosis plated on?
  103. What is the infective dose of M. tuberculosis?
    1 bacilli
  104. How do you control aerosols of M. tuberculosis?
    • Negative Pressure Rooms
    • Biosafety Cabinet
    • Safety carriers for centrifuge
    • Disinfectant soaked absorbent towels
    • Incinerator/Disposable loops
  105. What is the PPD/Manoux test?
    • Purified protein derivative
    • Intradermal injection of antigenic protein particles from killed M. tuberculosis
    • Delayed hypersensitivity reaction-localized swelling/redness
    • Reveals only previous infection-does not differentiate an active infection from latent infection or a cured patient
  106. What is PPD made from?
    antigenic protein particles from killed M. tuberculosis
  107. What are some side effects of PPD tests?
    Delayed hypersensitivity reaction-localized swelling/redness
  108. Can the PPD/Manyoux test be used to differentiate an active infection from latent infection or a cured patient?
    No. Reveals only previous infection-does not differentiate an active infection from latent infection or a cured patient
  109. Processing M. tuberculosis consists of what two parts?
    • -Digestion-releases mycobacteria from specimen material
    • N-acetyl-L-cysteine (NALC)
    • -Decontamination-kills off contaminating bacteria
    • 2% NaOH/4% NaOH
    • 5% Oxalic Acid
    • 4% H2SO4
  110. Digestion-releases mycobacteria from specimen material using which reagent?
    N-acetyl-L-cysteine (NALC)
  111. Decontamination-kills off contaminating bacteria
    • 2% NaOH/4% NaOH
    • 5% Oxalic Acid
    • 4% H2SO4
  112. What media is used to support the growth of mycobacteria?
    • Egg based, Lecithin in eggs neutralizes many toxic factors in specimens
    • Lowenstein-Jensen slants
    • Malachite Green
    • Gruft Modification with Antibiotics
  113. What ingredient in eggs is effective by neutralizing many toxic factors in specimens?
  114. What is the agar based medium used in culturing M. tuberculosis, that is sensitive to heat and light?
    7H11-transparent media
  115. What liquid based media is used for culturing M. tuberculosis?
    • Modified 7H9 broth
    • Bactec
    • Radiometric:    ↑ CO2 concentration
    • 9000MB:    ↓ O2 depletion
    • Biphasic
    • Isolator
    • Blood
  116. What is the incubation temp and time for culturing M. tuberculosis?
    • Temperature
    • 35-37°C for most cultures
    • 30°C media added for skin and joint cultures
    • CO2
    • Mycobacteria require 5-10% CO2 esp. during early phase of growth
    • Time
    • 6-8 weeks
  117. What organisms does the M. tuberculosis complex consist of?
    • M. tuberculosis
    • Most common cause of clinical tuberculosis
    • M. bovis
    • Primarily a disease of cattle
    • M. bovis has been irradicated from cattle in the U.S.
    • M. bovis BCG - strain of attenuated M. bovis used as TB vaccine
    • M. africanum, M. microti, & M. canettii
    • Rare causes of clinical tuberculosis
  118. What mycobacteria is the most common cause of clinical tuberculosis?
    M. tuberculosis
  119. What mycobacteria is the primarily a disease of cattle; has been irradicated from cattle in the U.S.; and can be attenuated for use as a TB vaccine?
    M. bovis
  120. What mycobacteria are rare causes of clinical tuberculosis?
    M. africanum, M. microti, & M. canettii
  121. How many of the world’s population is infected with TB
  122. How many of TB cases occur in racial and ethnic minorities?
  123. How many of TB cases are foreign-born individuals?
  124. Describe the initial infection of TB:
    • Bacilli are expelled when a person with active TB coughs, sneezes, sings, etc… Close contacts are at greatest risk.
    • Bacilli are inhaled and reach the pulmonary alveoli.
    • Immune response kills most of the bacilli leading to formation of granulomas.
  125. Describe the latent infection of TB:
    • Macrophages illicit a cell-mediated immune response and cause destruction of bacilli and formation of tubercules.
    • ~90% of people infected will have latent infection only
  126. Describe an active infection of TB:
    • TB overcomes the immune system, allowing mycobacteria to multiply, leading to TB disease.
    • Occurs most in those who lack a powerful cell-mediated immune response (e.g. kids, elderly, immunocompromised)
    • 1-5% of primary infections result in active infections
  127. Describe the reactivation of TB:
    • Decrease in the body’s defenses leads to release of bacilli and active infecton.
    • 5-9% of initial infections will result in reactivation TB.
  128. What is the clinical presentation of TB?
    Patients with active tuberculosis infection typically present with chronic low grade fever, night sweats, weight loss and most often a prolonged productive cough (>3 weeks).
  129. What are some diagnostic tests for TB?
    • Chest X-ray showing infiltrate or cavities in lungs which may be suggestive of TB.
    • PPD
    • AFB Smear/Culture
  130. What are methods of identifying TB?
    • Accuprobe
    •  Genprobe-Nucleic acid hybridization of a DNA probe to rRNA of the target organism.
    • Conventional Biochemical Testing
    •  68° Catalase Negative
    •  Nitrate Positive
    •  Niacin Positive
    • PCR/NYS “Fast Track” Program
    • Universal genotyping/DNA fingerprinting
    •  Spoligotyping/RFLP
  131. What genetic test is used in identifying TB?
    • Accuprobe
    • Genprobe-Nucleic acid hybridization of a DNA probe to rRNA of the target organism.
  132. What are conventional biochemical tests for TB?
    • 68° Catalase Negative
    • Nitrate Positive
    • Niacin Positive
  133. WHat treatment is used for active TB?
    • Active TB
    •  DOTS
    •   RIPE-for typical susceptible strains of Mtb in Non-HIV pts            Rifampin (RIF), Isoniazid (INH), Pyrazinamide (PZA), and Ethambutol (EMB) daily for 2 months, then        RIF and INH for 4 months
  134. WHat treatment is used for latent TB?
    INH daily for 9 months/Reduces risk of development of active TB from 10% to <1%
  135. WHat treatment is used for exposure to TB?
    INH for 9 months/may be discontinued if PPD remains Neg
  136. What susceptibility testing is performed on TB?
    • Broth or agar plates
    • 1st line drugs-RIPE and Streptomycin
    • 2nd line drugs-tested if any of 1st line show resistance
  137. What are causes of TB resistance?
    • In U.S. ~9% of Patients w/TB are resistant to at least 1 drug
    • Inadequate treatment
    • Mutation
    • Health Care infrastructure
  138. What are characteristics of MOTTs/NTMs (mycobacterium other than tuberculosis/non tuberculosis mycobacteria)?
    • Ubiquitous in nature: soil, water etc…
    • May colonize without causing disease
    • Non-photochromogens
  139. What is the most important MOTT (mycobacterium other than tuberculosis)?
    M. avium complex
  140. Which organism falls under the MOTT group of organisms and are non-photochromes?
    M. avium complex
  141. What is the transmission of M. avium complex?
    Aerosolization/Ingestion leads to respiratory or intestinal colonization
  142. What water-borne organism is implicated as a significant cause of death in AIDS patients?
    M. avium complex
  143. What is the primary species in M. avium complex?
    M. avium and M. intracellulare
  144. What are the patterns of pulmonary disease due to M. avium complex?
    • Associated primarily with patients with underlying lung disease (COPD, chronic bronchitis, lung cancer etc…)
    • Productive cough, weight loss, fever, bloody sputum (can be like TB)
  145. What are the patterns of disseminated disease due to M. avium complex?
    • Primarily AIDS pts - Severe immunosuppression greatest risk factor
    • Fever, sweats, fatigue, diarrhea, SOB
    • Wasting disease associated with CD4+ counts of <50 cells/ul
    • Prior to availability of antiretroviral medication, 30% of all HIV+ patients developed disseminated disease.  With highly active antiretroviral therapy incidence is only ~2%.
  146. Lymphadenitis is primarily found in children due to which organisms?
    M. avium complex
  147. How is M. avium identified?
    • Accuprobe
    • Conventional biochemicals:68°Cat Positive/Tellurite Positive
  148. What is the treatment for M. avium complex?
    • Combination of clarithromycin/azithromycin and ethambutol with or without rifabutin
    • Pulmonary MAC: 6 months/~90% chance of recovery
    • Disseminated disease: Maintenance therapy for life
    • Patients with low CD4+ counts get prophylactic TX w/HAART
    • Lymphadenitis in kids: no treatment necessary/benign course
  149. Which mycobacteria Requires hemin for growth; (chocolate plate or Middlebrook agar with “X” factor strip); Prefers 30°C and primarily causes skin and joint disease in AIDS patients
    M. haemophilum
  150. Which mycobacteria is most often seen in immunocompromised patients and the disease progression resembles TB-chronic pulmonary disease?
    M. kansasii
  151. What are the key biochemicals in identifying M. kansasii?
    Photo Positive, Nitrate Positive, Accuprobe available
  152. This organism is found in Fresh and Salt water and primarily causes cutaneous infections due to water-related trauma (fish tank, swimming pool, or natural water sources), prefers 30°C.
    M. marinum
  153. What organisms are considered schrotochromogens?
    M. scrofulaceum and M. gordonae
  154. What important pathogen is a cause of cervical lymphadenitis in children <5 years old and has been surpassed by M. avium complex as most common cause of lymphadenitis in developed countries?
    M. scrofulaceum
  155. This organism is very commonly found in water; Non-pathogenic
    Most commonly encountered “contaminant” in AFB Lab; Used as QA monitor to evaluate decontamination procedure; ~5% of total isolates should be M. gordonae:
    M. gordonae
  156. What mycobacteria are considered rapid growers?
    M. fortuitum complex, M. leprae,
  157. Why is it important to differentiate M. fortuitum from M. chelonae? How are they differentiated?
    M. chelonae is much more resistant

    • M.fortuitum species group:Salt tolerance, Iron uptake, and Nitrate POS
    • M. chelonae: Salt Tolerance, Iron Uptake, and Nitrate NEG
  158. What mycobacteria causes Hansen's disease?
    M. leprae
  159. Which mycobacterium does not grow on routine Media; Requires Cell Culture because it is characteristic of an Intracellular “parasite”?
    M. leprae
  160. What is the transmission of M. leprae?
    • Primary infection occurs through nose
    • Affects superficial nerve endings causing anesthetic skin lesions
    • If untreated can lead to sensory loss and paralysis
    • Natural infection in the footpads of wild armadillos
    • Primarily seen in Asia and Africa
    • In U.S. occasionally seen in Texas/Louisiana
  161. How do you identify M. leprae?
    • Rapid Identification
    • GLC/HPLC
    • Analysis of cell wall mycolic acids
    • HPLC used by many large laboratories and is very good at differentiating most documented species of Mycobacteria
    • or
    • Nucleic Acid sequencing
    • 16S rDNA sequencing
    • More widespread use has resulted in the recognition of many “new” genetically distinct species that have been previously uncharacterized.
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Microbiology Exam: Mycology