Lecture | Mycobacteria Flashcards
Aerobic, nonmotile, acid alcohol-fast (able to resist decolorization), slightly curved or straight bacilli
mycobacteria
M.tuberculosis complex (MTBC)
- Mycobacterium tuberculosis
- Mycobacterium bovis,
- M. bovis Bacille Calmette- Guérin strain [BCG]
- Mycobacterium caprae, Mycobacterium
pinnipedii, Mycobacterium africanum, Mycobacterium microtii, and Mycobacterium canettii
Nontuberculous mycobacteria are classified based on the pigment or known as
Runyon’s classification
classified as Slow-growers
Photochromagen, Scotochromogen, and Nonchromogen
- Battey Bacillus
- In AIDS patients
MYCOBACTERIUM AVIUM COMPLEX
“yellow bacillus,”
MYCOBACTERIUM KANSASII
growth requirement for hemoglobin or hemin
MYCOBACTERIUM HAEMOPHILUM
Bairnsdale ulcer
MYCOBACTERIUM ULCERANS
cultured from hot and cold water taps, hospital hot water generators and storage tanks, and other environmental sources.
MYCOBACTERIUM XENOPI
disseminated disease in HIV-infected patients
MYCOBACTERIUM GENAVENSE
chronic granulomatous infections involving skin and soft tissue, often called “swimming pool granuloma” or “fish tank granuloma”
MYCOBACTERIUM MARINUM
“Tap-water bacillus
MYCOBACTERIUM GORDONAE
etiologic agent of leprosy
MYCOBACTERIUM LEPRAE
also called Hansen’s disease
MYCOBACTERIUM LEPRAE
1 Lepra cells (cells that infect)
2 Not culturable;
3 Infects the nerves
MYCOBACTERIUM LEPRAE
Methods for Decontamination and Digestion of Mycobacteria
- N acetyl-L-cysteine (NALC) and 2-4% NaOH
- Trisodium phosphate and benzalkonium
chloride (ZEPHIRAN) - Dithiothreitol and NaOH
release mycobacteria trap in the mucin or in the cells.
digesting agent or 2-4% NaOH
- 0.2-0.6 micron in diameter and 1-4 micra in length
- Highly resistant to drying (protected from sunlight)
MYCOBACTERIUM TUBERCULOSIS
mycobacterium tuberculosis Putrifying sputum
WEEKS
mycobacterium tuberculosis Dried sputum
6-8 months
Droplets of dried sputum in the air
8-10 days
mycobacterium tuberculosis exposed to direct sunlight, organism for culture are killed within
2 hours
mycobacterium tuberculosis In sputum
20-30 hours
Disinfection of sputum
24 hours in 5% phenol
Easily killed by moist heat, boiling for 10
minutes, autoclave
mycobacterium tuberculosis
is the initial infection. The mycobacterium is eradicated by the host cellular immune response or walled off in a granuloma in the lung.
Primary tuberculosis
Primary tuberculosis Reactivation of latent infections can occur in immunocompromised individuals and cause
secondary tuberculosis.
in mycobacterium tuberculosis, a disseminated infection with multiple organ involvement.
Miliary TB
is miliary tuberculosis in the bones or spine
Pott’s disease
is used to detect MTB-infected individuals
Tuberculin skin test
purified protein derivative (PPD) is what type of antigen
MTB antigen.
Tuberculin skin test: positive test
hypersensitivity reaction at the injection site within 72 hours
Fluorochrome =
Auramine & Rhodamine
Gene Xpert =
new method
Cultures of mycobacteria are maintained for
8 week
Cultures of mycobacteria are Incubated at
35°C in the dark in 5%-10%
carbon dioxide
Liquid media
10 days - Löwenstein-Jensen (LJ) agar slant
Solid media
17 - Middlebrook 7H11 agar
standard for Isolating mycobacteria
Löwenstein-Jensen (LJ) agar slant
this agar contains coagulated whole eggs. glycerol, potato flour, and salts.
Löwenstein-Jensen (LJ) agar slant
in Löwenstein-Jensen (LJ) agar slant, what is is added to inhibit the growth of contaminating bacteria.
Malachite green
The disadvantage of this medium is that it becomes hydrolyzed when contaminants do grow on it, and the culture must be discarded.
Löwenstein-Jensen (LJ) agar slant
In what agar does M. tuberculosis colonies appear as cream-colored, dry, and wrinkled.
Middlebrook 7H11 agar.
In what agar does M. tuberculosis colonies appear as rough, buff-colored colonies that appeared within 3 weeks
Löwenstein-Jensen (LJ) agar slant
widely used medium for the isolation and antimicrobial susceptibility testing of mycobacteria. Although similar to Middlebrook 7H10 agar.
Middlebrook 7H11 agar
Middlebrook 7H11 agar con- tains casein hydrolysates that improve the recovery of
isoni azid-resistant strains of M. tuberculosis
M. avium strains on Middlebrook 7H11 agar can be distinguished from other M. avium-complex microorganisms, such as M. intracellulare, by their ability to grow at the temperature
45°C
M. avium on Lowenstein Jenson agar slant. appears as a
a film after 3 to 4 weeks of incubation.
on Lowenstein Jenson agar slant, its Colonies are buff-colored , but much smaller than M. tuberculosis
M. avium
bacteria with smooth colony type can appear as a “sun-spot” with starlike or asteroid margins
M. avium
bacteria with rough colony has a characteristic “lacy” appearance.
M. avium
a photochromogen, group I of Runyon’s classification
M. kansasii on Middlebrook 7H11 agar
classical method for differentiating the mycobacteria
M. kansasii
A characteristic feature of the photochromogens is their dependence on exposure
to light for pigment production
colonies of this bacteria have a strong yellow color
M. kansasii
a positive catalase reaction, reduction of nitrate to nitrite, and rapid hydrolysis of Tween 80, a detergent.
M. kansasii
on Middlebrook 7H11 agar. This rapid grower can appear on culture media within 2 to 4 days.
M. chelonae
M. chelonae can be distinguished from M. fortiatum because
- does not reduce nitrates or assimilate iron
- suceptible to polymyxin B and resistant to ciprofloxacin.
on chocolate agar it appear as smooth, opaque colonies resembling staphylococci or yeast
M. chelonae
Examined microscopically, the colonies appear dark and dense with smooth edges and a somewhat lighter center
Colony of M. chelonae
on Middlebrook 7H11 agar. The rapidly growing, rough colonies are shown after 3 days of incubation.
M. fortuitum
M. fortuitum can also grow on modified Mac- Conkey agar, without crystal violet, at temperature?
37°C
M. fortuitum can grow on 7H11 and LJ at temperaure?
43°C
M. fortuitum can grow in 5% NaCl at temperaure?
37°C
The rough colonies of M. fortuitum on Löwenstein-Jensen agar are shown growing after how many days of incubation
3 days
The rough colony of M. fortultum observed microscopically with
transmitted light
M. gordonae colonies on Middlebrook 7H11 agar.
Yellow- orange pigmented colonies
This species belong to the Runyon group II scotochromogens, characterized by pigmented colonies in the absence of exposure to light. Colony growth can appear in 3 weeks.
M. gordonae
M. gordonae colonies on Löwenstein-Jensen agar.
Yellow- orange pigmented colonies as well
Biochemical Test:
Reagent strip impregnated with substrate cyanogen halide = yellow
Niacin accumulation tests
Biochemical Test:
- Base on the ability to convert ferric ammonium citrate to an iron oxide
- Reddish brown or rust colored colonies
Iron uptake test
Biochemical Test:
1. Growth at 28°C on an egg based medium containing 5% NaCl.
2. All species of Mycobacteria are + except M. chelonae (-)
NaCl tolerance test
Two classes of catalase test
thermolabile and thermostable
In M. tuberculosis and M. bovis the enzymatic activity is inhibited at
68°C
Biochemical Test:
- solution of perhydrol 30% and Tween 80 at 10%
- height of the column of bubbles can be measured
Catalase test
Biochemical Test:
- detected by adding phenolphthalein to the colony/ substrate mixture and observing the formation of a pink color
Arylsulfatase test
species positive in Arylsulfatase test
- after three days: M. fortuitum and M. abcesuss
- after 2 weeks : M. gastri
Biochemical Test:
pyrazinamide is converted into pyrazinoic acid through the action of the pyrazinamidase enzyme
Pyrazinamide test
Biochemical Test:
- measures the presence of a lipase.
- Hydrolysis causes a pink color change
Tween 80 hydrolysis
