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Microbiology 2 > Bacillus > Flashcards

Bacillus Flashcards

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1
Q

The only important pathogenic species of Bacillus in domestic animals

A

Bacilllus anthracis

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2
Q

Principal Characteristics of Bacillus

A

large, Gram-positive, rods

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3
Q

Oxygen requirement of Bacillus

A

Aerobic, some are facultative anaerobic

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4
Q

Reproduction, fermentation, motility and enzyme test of Bacillus

A

Sporeforming

Most are catalase-positive, fermentative and non motile

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5
Q

Public Health Significance of Bacillus

A

Humans are infected through contact with infected animals, hide, hair, wool, excreta, and soil, and ingestion of spores from milk and meat,

Occupational disease

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6
Q

True or False: The spore of bacillus does not distend the sporangium and is smaller than the vegetative cell?

A

True

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7
Q

In what temperature can the spores of bacillus be visualized?

A

42 C
or
37 C at longer hours

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8
Q

Habitat and Ecology of Bacillus

A

Occur widely in nature: soil, water, air

Most common laboratory contaminants

Infected animals and animal product are reservoir

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9
Q

Habitat and Ecology of Bacillus anthracis

A

Associated with alkaline or calcareous soil, in which the spores can survive for many years.

Survival in soil is favored by a neutral or alkaline pH, an ambient temperature of 20 C to 37 C, and a relative humidity of 60% or higher

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10
Q

What virulence factor of Bacillus anthracis is carried by the plasmid?

A 
Genes coding for the 
exotoxin protein (pX01) and
polypeptide capsule (pX02)
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11
Q

Significance of the capsule of Bacillus anthracis

A

The capsule gives the virulence, non capsulated bacilli is non virulent

It is made up of poly-D glutamic acid, a protein, unlike other capsule which are made up of carbohydrates

Inhibits phagocytosis and interfere with opsonization

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12
Q

Component of media needed to trigger the organism produce capsules

A

Serum or bicarbonate

mucoid colonies = capsule formation

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13
Q

The three thermolabile components of Anthrax exotoxin complex

A

Factor 1 - Edema Factor - Edema
Factor 2 - Protective Factor - Antiphagocytic
Factor 3 - Lethal factor - Lethality

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14
Q

What is the alpha and beta subunit of the Anthrax exotoxin

A

Alpha - Factor 1/Edema Factor

Beta - Factor 2/Protective Factor

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15
Q

Mode of Action of Factor 1

A 
Calcium regulated
Increases Camp
Causes fluid & electrolyte loss
Prevent entry of Na & Cl ions
Creates osmotic effect
Edema formation
(affects all cell of the body)
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16
Q

Mode of Action of Factor 2

A

Promotes entry of edema factor and lethal factor

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17
Q

Mode of Action of Factor 3

A

Inducing apoptosis of activated macrophages, LT could prevent the release of chemokines and cytokines that alert the immune system to the presence of infecting B. anthracis, thereby facilitating the systemic spread of the infection

no effect on other cells

18
Q

Mode of Action of Anthrax Exotoxin Complex

A

PA binds & forms a heptamer to which EF and LF bind

Endocytosis and pH change causes fusion of PA with vesicle and release of LF and EF

Inhibit cell signaling and causes cell death

19
Q

Pathogenicity of Bacillus anthracis in Cattle

A

Most frequently seen in Cattle
Acute septicemia is more common
Cutaneous form following contamination of abrasions or wounds is occasionally observed

20
Q

Pathogenicity of Bacillus anthracis in Swine

A

Less susceptible than cattle
Subacute form; (Pharyngeal edema) pharyngitis with extensive swelling and hemorrhage in the region of neck and throat
Intestinal form with gastroenteritis also occurs

21
Q

Pathogenicity of Bacillus anthracis in Dogs and Cats

A

Rare but resembles that of Swine (Pharyngeal Edema)

22
Q

Pathogenicity of Bacillus anthracis in Humans

A 
Malignant carbuncle or pustule (most common)
Pulmonary Anthrax (Woolsorter's Disease, localized in Macrophanges, mediastinal hemorrhage)
Intestinal Anthrax (Necrotic Lesions with abdominal pain)
23
Q

Resistance of Vegetative cells of Bacillus anthracis

A

Vegetative cells in unopened carcasses may survive for up to 1-2 weeks (Killed at 60 C for 30 minutes)

24
Q

Resistance of Spores of Bacillus anthracis

A

Spores can persist for decades in a stable, dry environment. Spores are relatively resistant to heat and chemicals

Heat fixation of smears doesn’t kill spores

Killed by autoclaving (121C/15 minutes) and dry heat (150C/60 minutes, but not by boiling(100C) for under 10 minutes

25
Q

Resistance to disinfectants of Bacillus anthracis

A

Aldehydes, oxidizing and chlorinating disinfectant, ethylene oxide

Hides, hair, wool, bones and animal products not treated sufficiently to kill the spores may remain ineffective for years

26
Q

True or False: If anthrax is suspected, carcass should not be opened

A

True. Sporation can occur in abundant oxyegn and contaminate the air.

Let carcass rot to kill vegetative vell because of acidic products

27
Q

Sample collected for diagnosis in Septicemic form in cattle, sheep, and horses

A

Septicemic form.

Swabs from exuded blood or blood taken by syringe. Blood smears may also be submitted

28
Q

Sample collected for diagnosis in localized form in swine

A

Swabs from the cut surface of hemorrhagic lymph nodes or fluid or exudates aspirated from affected lymph nodes if the organism cannot be demonstrated in blood smears

29
Q

Stain used for the direct examination of Bacillus anthracis

A

Smears from tissues or blood contained from a superficial vein are stained with Gram’s, Giemsa’s, or Wright’s stain
(large, square-ended, gram-positive rods suggests anthrax)

stain with fluorescent antibodies against the cell wall or capsule of B. anthracis

30
Q

Expected appearance of Bacillus anthracis in isolation (blood agar, nutrient agar, microscopic examination)

A

Blood agar: colonies appear within 24 hours and are flat, rough, grey, and non-hemolytic

Nutrient agar: Colonies could be smooth and mucoid or rough (ground glass appearance

Microscopic examination: the edges of the colonies appear as a tangled mass of curly hairs (medusa head/judge’s wig)

31
Q

Bacillus species resembling Bacillus anthracis are called?

A

Anthracoids (e.g. B. subtilis, B. cereus, B. licheniformis, B megaterium, B. thuringiensis)

32
Q

Explain the Mcfadyean’s reaction

A

anthrax organism appears as blue color rods in pink stained amorphous polyglutamic acid capsule

33
Q

Explain the Ascoli test

A

Precipitation reaction. Used to detect anthrax in decomposed carcasses.

34
Q

Explain the String of Pearls test

A

Based on the principle of impairment of cell wall development by penicillin

Due to cell wall impairment it will produce colonies which will resemble string of pearls

35
Q

Antibiotic used against Bacillus anthracis

A

Penicillin

36
Q

What is a Stern Strain Vaccine

A

A live attenuated spore vaccine. With px01, but no px02 (no capsule=not pathogenic)

37
Q

What is a Anthrax Vaccine Adsorbed (AVA)?

A

Cell free filtrate of anthrax. Toxigenic but not capsulated

38
Q

Bacillus cereus

A

Bovine - gangrenous bovine mastitis

Cows and ewes - abortion

39
Q

Bacillus subtilis

A

Man - occasionally conjunctivitis

40
Q

Bacillus licheniformis

A

Bovine & ovine - abortion (but not the main cause)

41
Q

Geobacillus stearothermophilus

A

used to test the efficacy of autoclaving and other sterilizing procedure

42
Q

Bacillus piliformis

A

Tyzzer’s Disease

Gram negative, intracellular organism

Microbiology 2 (6 decks)

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