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Rotation: Microbiology > Mycobacteria > Flashcards

Mycobacteria Flashcards

(74 cards)

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1
Q

characteristics of mycobacteria

A

aerobic, non-spore forming, nonmotile straight or curved rods, cell walls are rich in lipids

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2
Q

gram stain of mycobacteria

A

ghost cells: faint, unstained images in the background material

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3
Q

why does mycobacteria stain poorly?

A

because the cell wall lipids interfere with the penetration of crystal violet and safranin into cell

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4
Q

acid-fast stain

A

using phenol to force mycobacterial cells to complex with a special dye

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5
Q

what makes an organism ‘acid fast’?

A

when the special dyes are retained in the cells even when treated with strong decolorizers like acid-alcohol

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6
Q

causative agent of tuberculosis

A

mycobacterium tuberculosis

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7
Q

how is mycobacterium tuberculosis (mtb) transmitted?

A

inhalation of droplet nuclei (small particles formed by coughing)

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8
Q

granulomas

A

tumorlike, inflammatory lesions that may occur in a variety of microbial diseases

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9
Q

tubercles

A
  • tuberculous granulomas
  • often have necrotic centers with a soft, cheesy appearance
  • caseous
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10
Q

primary tuberculosis

A

an infection in a previously uninfected individual

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11
Q

miliary tuberculosis

A
  • disseminated tuberculosis
  • small tubercles scattered throughout the body resemble millet seeds
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12
Q

body sites where mycobacterium tuberculosis (mtb) can cause disease

A
  • lungs
  • meninges
  • kidneys
  • bones
  • genital tractt
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13
Q

tuberculin skin test

A
  • injecting purified protein derivative, a mycobacterium tuberculosis (mtb) antigen, into the skin to observe for reaction within 48 to 72 hours
  • infected individuals become hypersensitive to mycobacterium tuberculosis (mtb) protein antigens
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14
Q

mycobacterium tuberculosis complex

A
  • mycobacterium tuberculosis
  • mycobacterium bovis
  • mycobacterium africanum
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15
Q

mycobacterium avium complex

A
  • mycobacterium avium
  • mycobacterium intracellulare
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16
Q

characteristics of mycobacterium avium complex

A
  • found in the environment
  • can cause pulmonary disease and mycobacterial lymphadenitis in immunocompetent individuals
  • can cause gastrointestinal or disseminated disease in patients with AIDS
  • most common cause of nontuberculous mycobacteria infections
  • resistant to many antimycobacterial drugs
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17
Q

mycobacterium fortuitum complex

A
  • mycobacterium fortuitum
  • mycobacterium chelonae
  • mycobacterium abscessus
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18
Q

characteristics of mycobacterium fortuitum complex

A
  • environmental mycobacteria that cause a variety of diseases including wound infections, abscesses, osteomyelitis, pulmonary infection
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19
Q

mycobacterium haemophilum

A
  • causes skin ulcers, lymphadenitis, disseminated disease in immunocompromised individuals
  • requires hemin, hemoglobin, or ferric ammonium citrate for growth
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20
Q

mycobacterium kansasii

A
  • common cause of nontuberculous mycobacterium pulmonary disease
  • infects variety of body sites including joints, bone marrow, skin, lymph nodes
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21
Q

mycobacterium leprae

A
  • causative agent of leprosy aka Hansen’s disease
  • does not grow in-vitro but can be grown in mouse footpads and armadillos
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22
Q

what is the diagnosis for leprosy based on?

A
  • patient’s clinical manifestations
  • presence of nonculturable acid-fast bacilli in skin biopsies
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23
Q

mycobacterium marinum

A
  • causes swimming-pool granuloma
  • acquired when traumatized skin comes in contact with fresh or salt water
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24
Q

mycobacterium scrofulaceum

A

causative agent of scrofula aka mycobacterial cervical lymphadenitis

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25
mycobacterium ulcerans
causes skin ulcers aka buruli ulcers or bairnsdale ulcers in africa and australia
26
other pathogenic mycobacterium
- mycobacterium genavense - mycobacterium simiae - mycobacterium xenopi - mycobacterium szulgai
27
mycobacterium gordone
common laboratory contaminant and is known as the 'tap-water bacillus' or 'tap-water scotochromogen'
28
other nonpathogenic mycobacterium
- mycobacterium flavescens - mycobacterium phlei - mycobacterium smegmatis - myobacterium terrae complex - mycobacterium baccae
29
what specimens can be submitted for mycobacterial cultures?
- respiratory tract specimens - gastric aspirates or lavages - urine - stool - blood - bone marrow - normally sterile body fluids - tissue - wound aspirate
30
what are inappropriate specimens for mycobacterial cultures?
- swabs - pooled sputum specimens - pooled urine specimens
31
how are mycobacterial specimens processed?
- concentration: more to inoculate - decontamination: to remove normal flora organisms and avoid overgrowing over mycobacteria - digestion: to free mycobacteria from clumps of protein and allows organisms to sediment during centrifugation
32
NALC + 2% NaOH Method
- NALC: mucolytic agent used to digest mucus - NaOH: decontaminates specimen - phosphate buffer: dilutes bactericidal activity of NaOH and lowers specific gravity of specimen to enhance sedimentation of mycobacteria during centrifugation - albumin: protein used to buffer and detoxify specimen sediments
33
ziehl-neelson stain
hot method; carbolfuchsin reagent must be heated for stain to work - smear is flooded with carbolfuchsin and heated until it has steamed for several minutes - after cooled, rinse with water - decolorized with acid alcohol - rinse slide and counterstain with methylene blue or brilliant green - rinse with water - acid-fast organisms: red with maybe beaded appearance - non-acid-fast organisms: blue or green depending on stain
34
kinyoun stain
cold method; carbolfuchsin reagent has high concentration of phenol and basic fuchsin and does not need to be heated
35
fluorochrome stain
uses auramine o which can be combined with rhodamine to stain acid-fast organisms
36
egg-based media
contain fresh eggs that have been inspissated and malachite green
37
nonselective egg-based medias
- petragnani: has high concentration of malachite green and used for specimens that are likely to be contaminated - american thoracic society medium: low concentration of malachite green and recommended for culturing body fluids - lowenstein-jensen medium: most commonly used
38
agar-based media
contain a variety of nutrients, albumin, and a very low concentration of malachite green
39
nonselective agar-based media
- middlebrook 7H10 - middlebrook 7H11
40
selective agar-based media
- mitchison's selective 7H11 (7H11S) - mycobactosel-middlebrook 7H11
41
liquid media
enriched with variety of nutrients and contains tween 80 - dubos tween albumin broth - middlebrook 7H9 broth - middlebrook 7H12 broth - middlebrook 7H13 broth
42
mycobacterium haemophilum culture media
requires hemin, hemoglobin, or ferric ammonium citrate for growth
43
what temperature are most mycobacterium incubated at?
35-37 C
44
what mycobacterium organisms have a lower optimal incubation temperature and at what temperature?
25-33 C - mycobacterium marinum - mycobacterium haemophilum - mycobacterium fortuitum complex - mycobacterium ulcerans
45
photoreactivity test
checks isolates for their ability to produce pigment and if pigmentation is induced by light
46
photochromogens
mycobacteria that produce pigment when exposed to light but not in darkness
47
scotochromogens
produce pigment in the light and in the dark
48
nonphotochromogens/nonchromogens
do not produce pigment in the light or in the dark
49
arylsulfatase
- test substrate: tripotassium phenolphthalein disulfate - pH indicator: phenolphthalein is produced when the sulfate group is removed form the substrate - sodium carbonate detects the free phenolphthalein to produce alkaline conditions and turn the phenolphthalein red **most mycobacteria are arylsulfatase positive and the test system is adjusted to be used as an identification tool
50
catalase
nearly all mycobacteria are catalase positive but the catalases produced by mycobacteria have different properties
51
heat-stable (68 C) catalase
- two tubes suspended with organism - one tube heated in a 68 C water bath for 20 minutes and one tube kept at room temperature - tween 80-hydrogen peroxide reagent is added to observe for mycobacterial clumps - bubbles are positive
52
semiquantitative catalase
measuring the amount of catalase produced by adding tween 80-hydrogen peroxide to an lowenstein-jensen deep and measuring the height of the bubble column - > 45 mm = high catalase producer - < 45 mm = low catalase producer
53
drop method (catalase)
used to test for isoniazid resistant mycobacterium tuberculosis strains by adding tween 80-hydrogen peroxide reagent to test colonies and observing for presence of bubbles - bubbles = susceptibility cannot be determined - no bubbles = presumptive resistance
54
iron uptake
testing for mycobacteria that can convert ferric ammonium citrate to iron oxide; positive results shows tan discoloration and rusty colored colonies
55
niacin accumulation
- all mycobacteria produce niacin but not all can convert it into nicotinic acid mononucleotide - for mycobacteria that cannot convert niacin, the niacin will accumulate which can be tested by adding water, cyanogen bromide, and aniline and left to sit for fifteen minutes - yellow color indicates the presence of niacin
56
nitrate reduction
inoculating the mycobacterial isolate into a tube with nitrate substrate for 2 hours and adding dilute HCl, sulfanilamide, N-naphthylethylenediamine dihydrochloride, and maybe zine if the red color does not appear after adding the other reagents
57
pyrazinamidase
testing for the presence of pyrazinamidase, an enzyme that deaminates pyrazinamide to form pyrazinoic acid and ammonia; pyrazinoic acid complexes with ferrous ammonium sulfate to form a pink color
58
tween 80 hydrolysis
detected by a color change that occurs when neutral red is released from tween 80-neutral red complexes; when neutral red is released from the complex, it turns red indicating a positive result
59
serpentine cords
mycobacterium tuberculosis are frequently arranged this way because of a special glycolipid known as cord factor which is responsible for ropelike or snakelike formations
60
identification characteristics of mycobacterium tuberculosis
- niacin and nitrate production - nap susceptible - negative 68 C catalase test
61
identification characteristics of mycobacterium bovis
- nap susceptible - 68 C catalase, niacin, nitrate negative ** only mycobacterium susceptible to tch
62
identification characteristics of mycobacterium kansasii
- photochromogen - loose strands colonies - on smears, appears long, broad, banded - hydrolyzes tween 80 - nitrate positive - high catalase producer
63
identification characteristics of mycobacterium marinum
- appears as long rods with cross bands in smears - photochromogen - grows best at 30 C - low catalase producer - hydrolyzes tween 80 and urease - pza positive - nitrate negative
64
identification characteristics of mycobacterium gordonae
- scotochromogen - nitrate negative - tween 80 positive
65
identification characteristics of mycobacterium scrofulaceum
- scotochromogen - nitrate negative - tween 80 hydrolysis negative - many strains are urease positive
66
identification characteristics of mycobacterium avium complex
- inactive biochemically - low catalase producers - tween 80, nitrate, urease negative
67
identification characteristics of mycobacterium xenopi
- most are nonchromogenic, some are scotochromogenic - distinctive bird's nest appearance - optimal incubation temperature is 42 C - nitrate, tween 80, urease negative
68
identification characteristics of mycobacterium fortuitum complex
- optimal incubation temperature is 28 C but grow rapidly at 37 C - arylsulfatase positive ** chelone and abscessus should be differentiate from fortuitum becuase they are more resistant to antibacterial agents used to treat infections - fortuitum reduces nitrate and takes up iron but chelone and abscessus do not
69
proportion test
using quadrant plates, control quadrant contains only culture medium while other quadrants contain culture medium and test drug at appropariate concentration to examine for growth compared to drug-free quadrant - resistant = growth in drug-containing quandrant is +1% of growth in control quadrant
70
mycobacterial photochromogens
- mycobacterium kansasii - mycobacterium marinum
71
mycobacterial scotochromogens
- mycobacterium gordonae - mycobacterium scrofulaceum - mycobacterium xenopi (some)
71
mycobacteria positive for tween 80
- mycobacterium kansasii - mycobacterium marinum - mycobacterium gordonae
72
mycobacterial nonphotochromogens/nonchromogens
- mycobacterium avium complex - mycobacterium haemophilum - mycobacterium ulcerans - mycobacterium xenopi (most)
72
mycobacteria positive for nitrate
- tuberculosis - kansasii - fortuitum

Rotation: Microbiology (5 decks)

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