Exam 4 (Mycobacteria spp.) Flashcards
Mycobacteria are acid fast due to:
High lipid content
Mycobacteria are Gram___ non-spore forming, slender, slow-growing___, obligate ___:
Gram+/variable
bacilli
obligate aerobes
Mycobacteria are divided into these two groups:
1) Mycobacterium tuberculosis complex
2) Non-tuberculosis mycobacteria (NTM)
T/F
All Mycobacterium tuberculosis complex are slow growers and produce non-pigmented colonies:
True
List the 8 species within the Mycobacterium tuberculosis complex:q
M. tuberculosis M. bovis M. bovis BCG M. africanum M. caprae M. canettii M. microti M. pinnipedii
Which species/strain of Mycobacterium tuberculosis complex has been used in live vaccines for over 70 years, and has led to infection in some patients:
M. bovis BCG
There are over ___ species of NTM, and some transiently colonize __, __, and ___ of healthy humans:
130 species
skin, GI, resp tract
Do NTM species typically spread person to person:
No.
What is the classification of NTM:
Runyon groups (I- IV)
This is an older classification system of NTM based on growth rate, colony morphology and pigment production (caratenoids):
Runyon groups
Photochromogens belong to Runyon Group___:
Group I
Scotochromogens belong to Runyon group___:
Group II
_____produce pigment in dark or light conditions and belong to Runyon group___:
Scotochromogens
Group II
____are non-pigmented regardless of incubation in dark or light conditions, and belong to Runyon Group___:
Non-photochromogens
Group III
____take fewer than 7 days to appear on solid media and belong to Runyon group__:
Rapid Growers
Group IV
Runyon Group IV:
Rapid Growers
Runyon Group III:
Non-photochromogens
List the 3 Mycobacteria species that are photochromogens (group I):
M. kansasii
M. marinum
M. asiaticum
List the 4 Mycobacteria species that are scotochromogens (group II):
M. scrofulaceum
M. szulgai
M. gordonae
This non-photochromogen is found in hot water taps in hospitals, and causes pulmonary infections and disseminated disease:
M. xenopi
This scotochromogen can cause cervical adenitis in children:
M. scrofulaceum
Why are M. avium and M. intracellulare reported in combination, as a complex:
On clinical grounds and routine lab methods, they cannot be distinguished from each other
Mycobacterium avium complex (MAC) is an important pathogen in ____ patients:
AIDS
Does pulmonary disease in AIDS patients present with granulomas or tissue death?
No.
Patients exhibit increased mucus production, can provide stress on bronchioles and lead to bronchiectasis.
Is MAC spread person to person?
No.
List the two Mycobacterium species in the Runyon group IV:
M. fortuitum
M. chelonae
What will Runyon group IV species grow on that most other Mycobacteria spp will not:
MacConkey (w/out crystal violet)
_____ and ____ from Runyon group ___ are the only 2 species that will grow in 5 days on MacConkey at 37 degrees C:
M. fortuitum
M. chelonae
This is a non-cultivatable nontuberculous mycobacterium, has not been grown in vitro because it is an obligate intracellular bacteria that only survives several minutes in the environment….is found in armadillos and mice:
M. leprae
Why can’t M. leprae be grown in vitro:
It is an obligate intracellular bacteria.
___ causes leprosy and is found in ___ and ___:
M. leprae
armadillos and mice
T/F
TB is increasing worldwide, and disease progression is becoming more rapid.
True.
There is a need for rapid isolation/identification.
What is the most important factor with growth of Runyon group IV species on MacConkey:
Most important factor is presence of growth in 5 days. Color change is not of great significance.
Describe a proper sputum specimen for Mycobacteria testing:
Sputum taken early morning for 3 consecutive days
**children with TB typically cannot cough up sputum
List some specimens for Mycobacteria spp testing:
Virtually any tissue or organ
- sputum
- tissue/granuloma
- urine
- bone, csf, blood, GI, stool
T/F
Specimens from sterile sites can be directly plated to media:
True
blood, urine, CSF
Processing of sputum specimens for acid fast bacteria requires ____/____ followed by ____ and ____ via centrifugation. These steps kill normal flora and also release TB bacteria from cells/mucin:
digestion/decontamination
neutralization and concentration
___: liquefy mucus with mucolytic agents which releases the bacteria from the mucin:
Digestion
Decontamination eliminates this:
mixed bacterial flora
What makes Mycobacterium resistant to decontamination:
High lipid cell wall
_____ with phosphate buffer or H20 is done following the 15 minute digestion/decontamination step:
Neutralization
What is used for digestion of mycobacterium:
NaOH
In the NALC NaOH method of sputum digestion/decontamination, NaOH is ____ when mixed with _____:
NaOH is reduced to 2% when mixed with NALC
____ is the preferred method for sputum digestion/decontamination and requires ____ minute incubation:
NALC NaOH
15
NALC is a ____ agent, releasing bacteria, while NaOH is both a ____ and ____ agent:
NALC: mucolytic
NaOH: mucolytic/decontaminating agent
What is done following the digestion/decontamination step:
add the phosphate buffer followed by 15 mins of centrifugation
What stain would be done to mucous specimen:
acid fast
after digestion, etc
What BSL___ lab is used to identify TB, and/or identify all Mycobacteria spp. and perform susceptibility testing:
BSL 3
BSL3 BSC and centrifuge room should have ______ walls and work surfaces, ____ air flow, and ____filters vented to outside:
non-permeable
directional
HEPA
What must be done with protective clothing after working in a BSL3:
removed/autoclaved
High ____cell content of Mycobacteria binds _____ and resists ____ by acid-alcohol:
Lipid
Fuchsin dye
decolorization
List the two methods of acid fast staining:
- Ziehl-Nelson (hot)
* Kinyoun (cold)
This acid fast staining method uses a higher concentration of phenol in the primary stain to accelerate the staining process and thus does not require heat:
Kinyoun (cold)
Fluorochrome stain is used for Mycobacteria spp. because they have an ____ for ____:
affinity for fluorochrome
You need to scan at least ____ oil immersion fields before you report a slide as _____:
300
negative
300 oil immersion fields is equivalent to ___ (400x) fields on on a fluorochrome slide:
30
For optimal recovery of Mycobacteria spp., you should use at least one _____ and one ____:
one solid media
one liquid medium
List the two liquid media used for Mycobacteria spp:
BACTEC 128 medium
Middlebrook 7H9 Broth
What two solid media should be used for Mycobacteria spp:
- one with agar base (Middebrook 7H10)
* one with egg-potato base (Lowenstein-Jensen, or Petragnani)
Both Lowenstein-Jensen and Petragnani media contain malachite green for this purpose:
Malachite green dye inhibits other microbes (contaminants)
How is tube media incubated for Mycobacteria spp:
35 C, dark, 5-10% CO2, humid
*tube initially in slanted position w/ cap loose for 1 wk to let fluid evaporate and CO2 enter
How often should Mycobacteria spp cultures be examined for growth, and when does growth for most species appear on liquid media, and solid media:
examine weekly
liquid: 2 wks
solid: 3-6 weeks
___ is often used as a back up if liquid media fails:
solid media
M. tuberculosis takes and average of ___ to grow and an additional ___ for susceptibility testing:
2-4 wks
2-4 wks
A new____ technique by Ghodbane is reducing the cultivation time for M. tuberculosis to as little as 72 hours:;
incubation
includes microaerophilic conditions
What is the immunodiagnostic test for TB and how does it work:
T-SPOT TB blood test
Wells contain TB specific antigen and thus detect TB activated T cells from blood samples
All Mycobacteria produce ___, some species lack the enzyme necessary to convert __ to ___, resulting in high accumulation of niacin in the culture medium:
niacin
niacin—-> niacin ribonucleotide
Is the niacin test enough to ID M. tuberculosis:
no
With the niacin filter paper test, what color will the broth turn if niacin is present (positive):
yellow
Which two species of Mycobacteria are Niacin+:
M. tuberculosis
M. simiae
Only two species of Mycobacteria produce nitroreductase, which catalyzes the reaction of nitrate reduction to nitrite:
M. tuberculosis
M. kansasii
It is very important controls be used for this test, and the M. tuberculosis control has to be strongly positive, otherwise results of unknowns are unreliable:
Nitrate reduction test
What enzyme reduces nitrate to nitrite, and which two species have the enzyme:
nitroreductase
M. tuberculosis
M. kansasii
Tween 80 hydrolysis is a ____ trade name, and is ___ to certain organisms:
detergent
toxic
This test identifies Mycobacteria possessing a lipase that splits the compound into oleic acid and polyoxyehtylated sorbitol:
Tween 80 hydrolysis
How do you perform a Tween 80 hydrolysis test:
- 2 drops Tween 80 added to 1mL saline and inoculated w/ loopful of organism
- incubate 35 C for ~12 days
- Fluid will change from light orange to pink or red if positive
What does a positive result look like in Tween 80 hydrolysis:
Fluid will change from light orange to pink or red
Which species is a quick positive for Tween 80 hydrolysis, and which are typically negative:
M. kansasii (positive)
M. tuberculosis complex (negative)
T/F
Most Mycobacteria species produce catalase:
True
T/F
All Mycobacteria species produce a heat stable catalase:
False.
*Most M. tuberculosis complex organisms do not produce heat stable catalase.(68 degree catalase neg)
____: Broth culture medium/automated continuous growth monitoring systems:
BACTEC
Positive niacin and nitrate reduction, 68 degree catalase neg, strong acid fast+, rough, dry, buff, non-pigmented on LJ media, slightly curved rods w/ beaded appearance:
M. tuberculosis
TB+ cultures are typically kept by the lab for ___ following ID for epidemiological purposes:
6-12 months
List the two conventional methods for M. tuberculosis susceptibility testing:
- Liquid broth automated systems (BACTEC)
* Absolute concentration (provides MIC)
Molecular methods for susceptibility testing for M. tuberculosis are testing for the gene/gene mutation that causes ___ resistance:
Rifampin
T/F
Inhalation of a single bacilli has been shown to lead to infection with Tuberculosis:
True
not necessarily disease though
Upon exposure to TB, ____% develop disease, ___ remain with latent infection:
5-10%
90%
T/F
One third of the world’s population is infected with TB:
True
latent or active
What is it called when person with latent TB has disease manifestation at a later time:
Secondary (reactivation) TB
Define miliary TB:
spread to other organs hematogenously
TB bacteria travel from respiratory droplets to alveoli, they are taken up by ___ which are unable to kill them, which leads to eventual formation of ____:
macrophages
granulomas
List the two clinical screening methods for TB:
- QuantiFERON-TB Gold In-Tube test
* Purified Protein Derivative (PPD)
Treatment consists of using ___ drugs in combination for ___ months:
- Isoniazid
- Rifampin
- Pyrazinamide
- Ethambuterol
2-3 drugs
9-12 months
*problems with patient compliance and drug resistance
Multidrug resistant TB is resistant to ___ and ____:
Isoniazid and Rifampin
Studies being done on association of ____ between Johne’s disease in cattle and Crohn’s disease in humans:
M. avium, subspecies paratuberculosis
M. leprae causes ____ aka ____:
leprosy
Hansen’s disease
This is a chronic disease of the skin, mucous membranes, nerve tissue, primary reservoir is humans, is usually associated with tropical climates, and is caused by an obligate intracellular bacteria:
Leprosy aka Hansen’s disease
M. leprae
What’s the significance of Molkai Hawaii:
Contact with infected human skin/nasal secretions transmits leprosy
Leprosy can be found in this part of the US, and ___serve as a reservoir:
SW
armadillos
Would a skin biopsy be part of confirming leprosy:
Yes
Can leprosy be cured:
Yes.
Antibiotics such as Clofazimie, Rifampin, Dapsone
