Microbiology Exam: Mycology

Card Set Information

Microbiology Exam: Mycology
2013-06-18 23:57:30

Show Answers:

  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 infections
    • Yeasts- Candida albicans
    • Colony morphology
    • Yeasts- Candida albicans
    • -Germ tube production
    • Yeast- Candida albicans
    • -Cornmeal morphology
  7. Yeasts- Other Candida species
    • C. tropicalis
    • C. krusei/inconspicua
    • C. parapsilosis
    • C. glabrata
  8. -Exists in nature
    -Causes disseminated disease
    • Yeasts-Cryptococcus neoformans
    • -Exists in nature
    • -Causes disseminated disease
  9. Colony Morphology
    Yeasts- C neoformans
  10. India Ink
    Yeasts- C neoformans
  11. Latex agglutination
    Yeasts- C neoformans
  12. Cornmeal morphology
    Yeasts- C neoformans
  13. Bird seed agar
    • Yeasts- C neoformans
    • -Phenol oxidase detection
  14. Other Cryptococcus species
    • Urease positive
    • Inositol assimilation positive
    • Round yeast cells only on cornmeal agar
  15. Causes disease in immunocompromised
    Can colonize healthy individuals
    Urease positive
    Yeasts- Trichosporon beigelii
  16. Colony morphology
    Yeasts- T beigelii
  17. Cornmeal morphology
    Yeasts- T beigelii
  18. Causes White Piedra
    Yeast- T beigelii
  19. Causes Tinea versicolor-
    (pityriasis versicolor)
    Yeasts- Malasezzia furfur
  20. Part of normal human flora
    Can cause disseminated infection
    Microscopic exam
    Yeasts- M furfur
  21. Special growth requirements- lipophilic
        so needs lipids or fatty
        acids to grow in vitro
    Yeasts- M furfur
  22. Other yeasts
    Base identification on morphologic and biochemical criteria
    • Morphology determined on cornmeal agar
    • Biochemical reactions- API’s or Vitek
  23. Aseptate (nonseptate)
    Molds- hyphae
  24. a.
    • Molds- hyphal pigmentation
    • a. Dematiaceous
    • b. Hyaline
  25. Have many different arrangements and sizes
    Helps to identify the mold
    Molds- spores
  26. Molds- Traditional Taxonomy
    -4 Phyla
    • Zygomycota
    • Ascomycota
    • Basidiomycota
    • Deutromycota
  27. Aseptate hyphae
    Rapid growers
    “lid popper”
    Asexual reproduction
  28. Zygomycota
  29. Septate hyphae
    Asexual reproduction
  30. Sexual reproduction
    Ascospores within 
  31. Septate hyphae
    Sexual reproduction –basidiospores
    Plant pathogens or environmental organisms
    Rarely cause human disease
  32. Contains mushrooms,
         rusts and smuts
  33. No sexual stage
    Septate hyphae
    Classified based on conidia
    Includes most saprobic and pathogenic fungi
  34. Molds-Practical Classification
    4 Categories
    • Superficial or cutaneous mycoses
    • Subcutaneous mycoses
    • Systemic mycoses
    • Opportunistic mycoses
  35. Infect hair, skin and nails
    Superficial Mycosis
  36. Confined to subcutaneous layer without spreading to other sites
    Subcutaneous Mycosis
  37. Contains the dimorphic fungi
    Primarily infects the lungs
    They may disseminate to any organ system
    Systemic Mycosis
  38. Found primarily in immunocompromised patients
    An ever-expanding list of organisms
    All may cause disseminated disease
    Opportunistic Mycoses
  39. 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
  40. Common Specimen Types
    • Respiratory tract specimens
    • Cerebrospinal fluid
    • Blood
    • Hair, skin and nail scrapings
    • Urine
    • Tissue, bone marrow and sterile body fluids
  41. 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
  42. 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
  43. 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
  44. Laboratory Safety Considerations
    • Molds
    • Laminar flow hood and tape plates
    • Yeasts
    • Can be handled on bench top
  45. 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
  46. Three groups of subcutaneous infections
    Chromoblastomycosis- warty lesions

    Mycetoma- mycelial tumor

    Phaeohyphomycosis- pigmented dark hyphae
  47. -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
  48. 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
  49. At site of trauma a chronic infection occurs characterized by draining sinus tracts, granules, and tumor-like deformities of subcutaneous tissue
  50. Bacterial cause- Nocardia, Streptomyces, and Actinomyces

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

    Direct microscopic exam yields dark fungal elements
  54. 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
  55. Phialophora richardsiae
    Microscopic –phialides with distinct flared saucer-like collarettes
  56. 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
  57. Dimorphic Mycosis Causes deep seated infections
    • Internal organs
    • Lymph nodes
    • Bone
    • Subcutaneous tissue and skin
  58. 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
  59. 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
  60. 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
  61. 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
  62. Sporothrix cont’d
    Primary lesion forms
    Non-healing ulcer
  63. Sporothrix cont’d
    Secondary lesions

    • Nodular lesions
    • Lymphatic channels and nodes
    • Rarely disseminates systemically
  64. Sporothrix
    Direct detection from sample
    • Exudate from lesions
    • Silver stain may show cigar shaped yeast cells
  65. Sporothrix culture from sample
    • Culture –mold phase
    • Leathery ,wrinkled colonies that darken with age
    • Young colonies could be mistaken for yeast
  66. 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
  67. Sporothrix Culture –yeast phase
    • Try to convert at 37C on enriched media
    • Cream colored yeast colony
    • Cigar shaped yeast cells- cigar bodies
  68. What are the Endemic areas for Sporothrix?
    • Found world-wide
    • Outbreaks in gold mines
  69. 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
  70. What is the etiology of Histoplasma?
    • Pulmonary lesion- primary infection
    • Chronic pulmonary disease- cavitations
    • Secondary dissemination- lymphatics, organs and skin
  71. Histoplasma Direct detection
    • Respiratory tract specimens
    • Bone marrow, tissue or blood by Giemsa may yield round/oval yeasts within macrophages
    • PCR on tissue
  72. 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
  73. Histoplasma Sepedonium
    saprobic mold that looks similar but grows faster
  74. Histoplasma Culture
    • Yeast phase –difficult to convert, not recommended
    • Microscopic –small yeast cells
  75. 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
  76. How is Blastomyces dermatitidis acquired?
    • Acquired by inhalation of conidia
    • Disease state very similar to Histoplasmosis
    • More common in men associated with outdoor occupation
  77. What is characteristic of a primary Blastomyces infection?
    • respiratory infection
    • Dissemination to bones, soft tissue, and skin
  78. 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
  79. Describe Blastomyces culture during mold phase:
    • White, waxy to cottony colony
    • Microscopic –single, round to pyriform conidia on conidiophores = “lollipop”
  80. Describe Blastomyces culture during yeast phase:
    • Waxy, wrinkled colonies
    • Relatively easy to convert
    • Microscopically –large thick-walled yeast with broad base
  81. 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
  82. Coccidioides immitis
    Source of infection
    • Acquired by inhalation of arthroconidia
    • Mold phase grows on vegetation producing airborne arthroconidia
  83. 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
  84. 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
  85. Coccidioides Culture
    • mold phase
    • Cottony white colony
    • Highly contagious!!!
  86. 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
  87. 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”
  88. Paracoccidioides brasiliensis
    • Dimorphic fungi
    • Endemic in South America
    • Diagnostic form –yeast phase known as “Mariners Wheel”
    • Mold phase –similar to Blastomyces
  89. Others possible systemic mycoses
    • Zygomycosis
    • Candidiasis
    • Aspergillosis
    • Cryptococcosis
  90. What is the only genus in family Mycobacteriaceae?
  91. What are the only two species that are contagious in the family Mycobacteriaceae?
    M. tuberculosis and M.leprae
  92. What are the characteristics of Mycobacteriaceae?
    • Obligate aerobes
    • Slightly curved rods
    • Acid-Fast
  93. How many organisms are required for an acid fast smear?
    Requires 5,000-50,000 orgs/ml to show a positive smear
  94. What stains are used on acid fast organisms?
    • Fluorochrome stains
    • Carbol Fuchsin stains
  95. 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
  96. What is the generation time of mycobacteriacea?
    Very long, 2 to 20 hours.
  97. What is the optimal temperature for AFBs (acid-fast bacilli)?
    • Optimal Temperature for most AFB is 35-37°C
    • Some prefer 30°C
  98. How is non tuberculosis mycobacterium classifeid?
    • Pigment-Runyoun 1959 to classify NTM
    • Nonphotochromogens
    • Photochromogens
    • Scotochromogens
    • Rapid Growers
  99. What is M. tuberculosis plated on?
  100. What is the infective dose of M. tuberculosis?
    1 bacilli
  101. How do you control aerosols of M. tuberculosis?
    • Negative Pressure Rooms
    • Biosafety Cabinet
    • Safety carriers for centrifuge
    • Disinfectant soaked absorbent towels
    • Incinerator/Disposable loops
  102. 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
  103. What is PPD made from?
    antigenic protein particles from killed M. tuberculosis
  104. What are some side effects of PPD tests?
    Delayed hypersensitivity reaction-localized swelling/redness
  105. 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
  106. 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
  107. Digestion-releases mycobacteria from specimen material using which reagent?
    N-acetyl-L-cysteine (NALC)
  108. Decontamination-kills off contaminating bacteria
    • 2% NaOH/4% NaOH
    • 5% Oxalic Acid
    • 4% H2SO4
  109. 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
  110. What ingredient in eggs is effective by neutralizing many toxic factors in specimens?
  111. What is the agar based medium used in culturing M. tuberculosis, that is sensitive to heat and light?
    7H11-transparent media
  112. What liquid based media is used for culturing M. tuberculosis?
    • Modified 7H9 broth
    • Bactec
    • Radiometric:    ↑ CO2 concentration
    • 9000MB:    ↓ O2 depletion
    • Biphasic
    • Isolator
    • Blood
  113. 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
  114. 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
  115. What mycobacteria is the most common cause of clinical tuberculosis?
    M. tuberculosis
  116. 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
  117. What mycobacteria are rare causes of clinical tuberculosis?
    M. africanum, M. microti, & M. canettii
  118. How many of the world’s population is infected with TB
  119. How many of TB cases occur in racial and ethnic minorities?
  120. How many of TB cases are foreign-born individuals?
  121. 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.
  122. 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
  123. 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
  124. 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.
  125. 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).
  126. 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
  127. 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
  128. What genetic test is used in identifying TB?
    • Accuprobe
    • Genprobe-Nucleic acid hybridization of a DNA probe to rRNA of the target organism.
  129. What are conventional biochemical tests for TB?
    • 68° Catalase Negative
    • Nitrate Positive
    • Niacin Positive
  130. 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
  131. WHat treatment is used for latent TB?
    INH daily for 9 months/Reduces risk of development of active TB from 10% to <1%
  132. WHat treatment is used for exposure to TB?
    INH for 9 months/may be discontinued if PPD remains Neg
  133. 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
  134. 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
  135. 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
  136. What is the most important MOTT (mycobacterium other than tuberculosis)?
    M. avium complex
  137. Which organism falls under the MOTT group of organisms and are non-photochromes?
    M. avium complex
  138. What is the transmission of M. avium complex?
    Aerosolization/Ingestion leads to respiratory or intestinal colonization
  139. What water-borne organism is implicated as a significant cause of death in AIDS patients?
    M. avium complex
  140. What is the primary species in M. avium complex?
    M. avium and M. intracellulare
  141. 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)
  142. 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%.
  143. Lymphadenitis is primarily found in children due to which organisms?
    M. avium complex
  144. How is M. avium identified?
    • Accuprobe
    • Conventional biochemicals:68°Cat Positive/Tellurite Positive
  145. 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
  146. 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
  147. Which mycobacteria is most often seen in immunocompromised patients and the disease progression resembles TB-chronic pulmonary disease?
    M. kansasii
  148. What are the key biochemicals in identifying M. kansasii?
    Photo Positive, Nitrate Positive, Accuprobe available
  149. 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
  150. What organisms are considered schrotochromogens?
    M. scrofulaceum and M. gordonae
  151. 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
  152. 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
  153. What mycobacteria are considered rapid growers?
    M. fortuitum complex, M. leprae,
  154. 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
  155. What mycobacteria causes Hansen's disease?
    M. leprae
  156. Which mycobacterium does not grow on routine Media; Requires Cell Culture because it is characteristic of an Intracellular “parasite”?
    M. leprae
  157. 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
  158. 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.