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BACTE MIDTERMS > 4.4 > Flashcards

4.4 Flashcards

1
Q

What is the size range of Mycobacteria?

A

0.2 to 0.6 µm x 1 to 10 µm

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2
Q

Are Mycobacteria motile, spore-forming, or encapsulated?

A

No, Mycobacteria are nonmotile, non-spore-forming, and non-encapsulated.

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3
Q

What feature of the Mycobacterial cell wall contributes to acid fastness?

A

The presence of N-glycolylmuramic acid and a high lipid content.

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4
Q

What type of respiration do Mycobacteria exhibit, and what enzyme activity are they known for?

A

Mycobacteria are strictly aerobic and catalase positive.

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5
Q

What appearance is often observed in Mycobacteria due to Much’s granules?

A

A beaded appearance, with Much’s granules being non-acid-fast and gram-positive.

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6
Q

What structural formations can Mycobacteria exhibit microscopically?

A

Palisade or snapping formations, including X, Y, V, and L forms.

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7
Q

How quickly do rapidly growing Mycobacteria grow, and at what temperature range?

A

They grow on simple media in 2 to 3 days at 20°C to 40°C.

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8
Q

How long do Mycobacteria associated with disease take to grow, and on what type of media?

A

They require 2 to 6 weeks of incubation on complex media.

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9
Q

What is the optimal pH range for Mycobacterial culture media?

A

6.5 to 6.8

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10
Q

What is the generation time for Mycobacteria?

A

Greater than 12 hours

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11
Q

What type of medium is required for the primary isolation of Mycobacterium tuberculosis (MTB)?

A

A complex medium containing egg-potato base or serum-agar base

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12
Q

What environmental conditions are needed for MTB growth?

A

Very slow growth (10–20 days for visible colonies).
Requires increased CO₂ tension (5–10%) at 37°C.

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13
Q

Describe the appearance of MTB colonies.

A

Initially: Small (1–2 mm), dry, friable, rough, warty, granular, and buff-colored.
Later: Flat irregular margins with a “cauliflower-like” center.

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14
Q

What enhances MTB growth, and how is this described?

A

Glycerol enhances growth, described as eugenic growth (luxuriant growth).

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15
Q

What is the replication time of MTB?

A

20–22 hours

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16
Q

What factors enable MTB to resist adverse environmental conditions?

A

Intracellular existence in the body.
Resistance to drying, heat, and chemical agents

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17
Q

What are the main virulence factors of MTB,

A

Cord Factor (Trehalose-6,6’-dimycolate)
Sulfatides

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18
Q

Responsible for tight serpentine cords and cord formation.

A

Cord Factor (Trehalose-6,6’-dimycolate)

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19
Q

Glycolipids that react with neutral red and are associated with virulent MTB strains.

A

Sulfatides

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20
Q

What is the primary disease caused by MTB, and how is it transmitted?

A

Primary Tuberculosis: Chronic granulomatous infection of the respiratory tract.

Transmission: Inhalation of infected droplets (1–5 µm).

21
Q

What are the key symptoms of primary tuberculosis?

A

Cough,
hemoptysis,
chest pain,
dyspnea,
low-grade fever,
night sweats,
fatigue,
anorexia, and
weight loss.

22
Q

Hypersensitivity to MTB proteins, indicating past or recent TB infection.

A

Tuberculin Test

23
Q

What reagents are used in tuberculin testing?

A

Old Tuberculin (OT): Prepared from boiled broth cultures.

Purified Protein Derivative (PPD): Mixture of small tuberculoproteins

24
Q

What methods are used for tuberculin test administration?

A

Mantoux Test (intracutaneous injection).

Von Pirquet Test (skin scratching).

Vollmer Patch Test (cloth soaked in OT/PPD placed on skin).

Moro Percutaneous Test (OT/PPD + lanolin rubbed onto skin).

Tuberculin Tine Test (multiple punctures)

25
Q

How is the tuberculin test interpreted?

A

Read at 48–72 hours.

Measure induration:

≥10 mm = Positive.

5–10 mm = Doubtful (other mycobacteria).

<5 mm or erythema without induration = Negative

26
Q

Hematogenous spread of MTB, seeding multiple organs (spleen, liver, lungs, bone marrow, kidneys, etc.).

A

Miliary TB

27
Q

MTB invades the spinal vertebrae, causing back pain

A

Pott disease

28
Q

Pott disease Also known as

A

skeletal TB or tuberculosis spondylitis

29
Q

Name other forms of extrapulmonary TB.

A

Pleural TB (pleurisy).
Lymphadenitis (painless head or neck swellings).
Meningeal TB (rupture into subarachnoid space).
Genitourinary infections (kidneys/genital organs).
Peritoneal TB.
Gastrointestinal TB.

30
Q

What are the first-line antituberculosis drugs?

A

Rifampin,
Isoniazid (INH),
Pyrazinamide (PZA), and
Streptomycin

31
Q

What defines Multidrug-Resistant TB (MDR-TB)?

A

Resistance to at least isoniazid and rifampin

32
Q

What defines Extensively Drug-Resistant TB (XDR-TB)?

A

Resistance to:

Isoniazid and rifampin.
Any fluoroquinolone.
At least one injectable second-line drug (e.g., amikacin, kanamycin, or capreomycin).

33
Q

Biochemical Tests for MTB

A

Niacin Accumulation: Positive.
Nitrate Reduction: Positive.
Catalase: Positive.
Heat-stable Catalase (68°C): Negative.
Arylsulfatase: Negative.
Pyrazinamidase: Positive.
Inhibited by NAP: Positive.
Resistance to T2H: Positive.

34
Q

What is the primary host for Mycobacterium bovis

A

Primarily cattle, but also dogs, cats, swine, parrots, and humans

35
Q

What is the transmission route for Mycobacterium bovis

A

Ingestion of contaminated milk or exposure to infected animals

36
Q

What vaccine is derived from M. bovis?

A

Bacillus-Calmette-Guerin (BCG),

37
Q

used for newborn vaccination against TB.

A

Bacillus-Calmette-Guerin (BCG)

38
Q

Describe the cultural characteristics of M. bovis colonies on Egg-based media

A

Slow-growing, small, granular, rounded, nonpigmented colonies with irregular margins after 21 days at 37°C.

39
Q

Describe the cultural characteristics of M. bovis colonies on Middlebrook 7H10 medium

A

Similar colonies to MTB but slower to mature

40
Q

What medium component selectively inhibits M. bovis growth

A

Glycerol

41
Q

Biochemical characteristics of M. bovis?

A

Niacin accumulation: Negative.
Nitrate reduction: Negative.
Heat-stable catalase: Negative.
T2H (Thiophene-2-carboxylic acid hydrazide): Sensitive.
Serpentine cords: Present in smears

42
Q

Where is Mycobacterium africanum associated with human TB cases?

A

Tropical Africa.

43
Q

What specialized test is used for M. africanum detection?

A

Spoligotyping (spacer oligotyping).

44
Q

What are the biochemical characteristics of M. africanum?

A

Urease: Positive.
Variable growth in TCH (Thiophene-2-carboxylic acid hydrazide).

45
Q

Smooth strain of MTB, grows more rapidly (6 days on solid media).

A

Mycobacterium canetti

46
Q

From which patient population was M. canetti first isolated?

A

An AIDS patient with mesenteric TB

47
Q

Biochemical characteristics of M. canetti?

A

Niacin: Positive.
Nitrate reduction: Positive

48
Q

Which patient populations are affected by Mycobacterium microti?

A

Both immunocompetent and immunocompromised individuals.

49
Q

Isolated from TB patients, indicating its clinical relevance in human infections.

A

M. microti

BACTE MIDTERMS (17 decks)

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