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Microbiology > Bacillus > Flashcards

Bacillus Flashcards

1
Q

difference between spores of bacillus and clostridium?

A

spores of bacillus are of the same width as that of bacteria and do not produce bulge in the bacterial cell wall

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2
Q

what is the difference in motility between bacillus anthracis and other bacilli?

A

bacillus anthracis is non-motile, most have peritrichous flagella

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3
Q

why is anthrax bacillus historically relevant? #morphology

A

1st to be-

a) seen under microscope
b) first to be transmitted
c) first to be isolated
d) first to be used for vaccination

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4
Q

what gram stain does bacillus anthracis give? #morphology

A

gram positive

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5
Q

what acid fast stain does bacillus anthracis give? #morphology

A

acid fast negative

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6
Q

what part of bacillus anthracis is missing in human tissue but is present in culture?
describe them #morphology

A

spores

spores are oval/spherical, centrally located, same width as that of vegetative cell

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7
Q

what part of bacillus anthracis is missing in culture but is present in human tissue?
what is it in nature? #morphology

A

capsule,

it is polypeptide in nature

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8
Q

under what conditions are spores formed?

give two things that encourage spore formation #morphology

A

unfavourable conditions

distilled water and 2% NaCl

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9
Q

what inhibits formation of spores? #morphology

A

calcium chloride

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10
Q

what is McFaydean’s reaction used for? #morphology

A

used for presumptive diagnosis of anthrax

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11
Q

anthrax is a disease primarily for and secondarily for?

A

animals, humans

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12
Q

describe mechanism of McFaydean’s reaction #morphology

A

blood films containing anthrax are stained with polychrome methylene blue. After 10-12 seconds, amorphous purple material is noticed around the bacilli.
It represents the disintegrated capsular material which is characteristic of anthrax bacilli.

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13
Q

in cultures, what specific type of appearance do anthrax bacilli colonies have? #morphology

A

they have a “bamboo-stick appearance”

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14
Q

what does giemsa stain show? #morphology

A

it stains bacillus purple and capsule red

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15
Q

what is the temperature range for growth of anthrax bacilli?

what is the optimum temp.? #culture

A

12-45 degree celsius,

35-37 degree celsius

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16
Q

describe anthrax bacilli in nutrient agar media #culture

A

raised, opaque, greyish white colonies

“medusa head appearance”- interlacing chains of bacilli around the edge of the colonies resembling locks of matted hair

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17
Q

describe anthrax bacilli in blood agar media #culture

A

non-haemolytic though occasional strains produce narrow zone

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18
Q

describe anthrax bacilli in gelatin stab culture #culture

A

“inverted fir tree appearance”- liquefied mostly at the top because it is an aerobe

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19
Q

name selective medium for anthrax bacilli

name some components #culture

A

PLET medium

polymyxin, thallous acetate

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20
Q

solid medium containing pencillin #culture

A

“string of pearls reaction”- when anthrax bacilli is grown on solid medium containing penicillin, in 3-6 hours the cells become large, spherical and resemble a string of pearls

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21
Q

what is the importance of a string of pearls reaction? #culture

A

only b.anthracis gives positive but not b.cereus

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22
Q

2 differences between b. anthracis and b. cereus

A
  1. string of pearls reaction for b. anthracis

2. gammaphage lysis for b. anthracis

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23
Q

what sugars are fermented by b. anthracis? #biochemicalreactions

A

glucose, maltose, sucrose

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24
Q

what is the result of anthrax bacilli on catalase test? #biochemical reactions

A

positive

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25
Q

what is the result of anthrax bacilli on nitrates?

A

reduces nitrates to nitrites

26
Q

what is the resistance of anthrax bacilli to heat?

A
  1. vegetative state- 60 degree celsius in 30 minutes

2. spore state- dry heat 140 degree celsius 1-3 hours, boiling 10 minutes

27
Q

2 methods to destroy anthrax bacilli

A
  1. 4% potassium permanganate in 15 mins

2. autoclave in 15 mins (121 degree celsius)

28
Q

2 methods to destroy anthrax bacilli in animal products and wool

A
  1. duckering- 2% formaldehyde 30-40 degree celsius for 20mins
  2. disinfection of wool- 0.25% 60 degree celsius for 6 hours
29
Q

3 antibiotics that anthrax is susceptible to

A

penicillin, streptomycin, erythromycin

30
Q

three antigens of anthrax bacilli and respective nature

A
  1. capsular antigen- polypeptide, acts as hapten
  2. cell wall antigen- polysachharide
  3. somatic antigen- heat labile protein, acts as antibody
31
Q

two factors that determines virulence of anthrax

A
  1. capsular polypeptide

2. anthrax toxin complex

32
Q

what does the anthrax toxin complex comprise of?

A
  1. PA (protective antigen) factor
  2. OF (oedema factor)
  3. LF (lethal factor)
33
Q

function of PA

A

binds to receptor on target cell surface and provides attachment site for OF or LF

34
Q

function of OF

A

Oedema factor is an adenyl cyclase which causes intracellular accumulation of cAMP causing oedema

35
Q

function of LF

A

causes cell death

36
Q

how does capsular polypeptide cause virulence

A

controlled by plasmid and inhibits phagocytosis

37
Q

describe pathogenesis of anthrax in animals

A

in cattle and sheep by ingestion of spores
not by direct animal-to-animal contact
infected animal released bacilli from mouth, nose, rectum

38
Q

how are humans affected by anthrax? name 3 routes. what’s common between them?

A 
humans are affected secondarily by animals
1. cutaneous
2. pulmonary
3. intestinal
common- septicemia and meningitis
39
Q

cutaneous anthrax-

  1. etiology
  2. affected sites
  3. characteristic features
  4. prognosis
A
  1. by entry of spores into abraded skin- farmers and people holding carcasses
  2. face, neck and hands
  3. formation of pustule, acute inflamm. reaction causing congestion and oedema with central lesion called “black eschar”/malignant pustule
  4. generally resolves by itself, sometimes fatal septicemia
40
Q

pulmonary anthrax-

  1. etiology
  2. affected sites
  3. characteristic features
  4. prognosis
A
  1. inhalation of dust or filaments of wool in factories; “wool sorter’s disease”
  2. lungs
  3. haemorrhagic bronchopneumonia, septicemia HIGH FATALITY
41
Q

intestinal thorax-

  1. etiology
  2. characteristics
  3. prognosis
A
  1. rare in man, by eating improperly cooked meat
  2. violent enteritis with bloody diarrhoea
  3. high case fatality
42
Q

what are the steps in lab diagnosis?

A
  1. specimen collection
  2. microscopy
  3. culture
  4. serology
  5. inoculation
  6. PCR
43
Q

specimen collection in anthrax

A

cutaneous anthrax: swabs, fluid or pus- from pustules
pulmonary anthrax: blood samples
intestinal anthrax: peritoneal fluid or faecal samples

44
Q

microscopy in anthrax

A

positive gram stain,
DFA (direct flourescent antibody test)
cell wall antigen test
mc-faydean’s reaction

45
Q

inoculation in anthrax

A

white mouse/guinea pig die with 36-48 hours

46
Q

serology in anthrax

A

ASCOLI’S THERMOPRECIPITIN TEST:
tissues ground up in saline and boiled for 5 mins, then extract is layered over anti-anthrax serum in a narrow tube- rings appears at the junction of 2 liquids within 5 minutes

47
Q

when is ascoli’s thermopreciptin important?

A

for rapid diagnosis when sample is putrid

48
Q

polymerase chain reaction is used for?

A

confirmation of anthrax bacillus

49
Q

2 medicines for treatment of anthrax

A

doxycycline

ciproflaxin

50
Q

prophylaxis of anthrax

A

factory hygiene, sterilisation of animal products
vaccines for humans- PA vaccines and live attenuated vaccines
vaccines for animals- Sterne vaccine

51
Q

what are the 2 types of PA vaccine?

A

AVA (adsorbed) and AVP (precipitated)

52
Q

what is sterne vaccine composed of?

A

spores of non-capsulated avirulent strain

53
Q

route of administration of PA vaccines? doses?

A

intramuscular, 5 doses for AVA and 4 doses for AVP

requires annual booster

54
Q

route of administration of live attenuated vaccines?

A

subcutaneous

55
Q

what are anthracoid bacilli/pseudoanthrax baciili?

A

aerobic spore bearing bacilli resembling b. anthracis

56
Q

name 3 anthracoid bacilli

A
  1. lichenforms- food poisoning
  2. stearothermophilus- autoclave testing
  3. subtilis- eye infection
57
Q

what does bacillius cereus cause? types?

A

food poisoning

1. short incubation period and 2. long incubation period

58
Q

features of short incubation period food poisoning

A
  1. acute nausea and vomiting
  2. 1-5 hours
  3. from cooked rice in Chinese restaurants
  4. RARE diarrhoea
59
Q

features of long incubation food poisoning

A
  1. acute abdominal pain and diarrhoea
  2. 8-16 hours later
  3. RARE vomiting
  4. contaminated food
60
Q

pathogenesis in B. Cereus is because of?

A

enterotoxin production: diarrhoeal type- e. coli type enterotoxin and emetic type- staphylococcal type enterotoxin

61
Q

3 differences between B. Cereus and B. Anthracis?

A
  1. non-motile/motile
  2. no lysis/lysis by gammaphage
  3. no DFA test/ DFA test
  4. non-capsulated/capsulated

Microbiology (1 decks)

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