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MICROBIOLOGY II > Lecture 6- Bacillus > Flashcards

Lecture 6- Bacillus Flashcards

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1
Q

What phylogenetic branch does bacillus belong to

A

Firmicutes (based on 16S rRNA sequencing)

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2
Q

Is bacillus a spore former

A

Yes it sporulates

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3
Q

Bacillus is gram negative - true or false

A

FALSE

Bacillus is gram positive

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4
Q

What shape is bacillus

A

Rod

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5
Q

Is bacillus catalase positive or negative

A

Catalase positive

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6
Q

Is bacillus aerobic or anaerobic

A

Aerobic

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7
Q

Where are the spores of bacillus found

A

Oval/central spores (no distension of sporgangium)

Spore fit within cell - no swelling

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8
Q

Bacillus is considered motile except for one species - which is it

A

Anthrax

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9
Q

What is specific about bacillus metabolism

A

It is very diverse - no typical bacillus

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10
Q

What are the three key species of bacillus

A

MESOPHILES - B.cereus, B. Anthracis and B.subtilis

INSECT PATHOGEN - B. Thuringiensis - toxic to insects so use as pesticide. Also in GM crops

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11
Q

What are the paenibacillus

A

Almost bacillus.

Reclassified 1993

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12
Q

Which did ferdinand cohn do in 1872

A

Work in spores of b. Subtilis and prove spores move transiently from spore to bacteria (spore and germination life cycle)

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13
Q

What fundamental work did r. Koch do in 1876 with a bacillus species

A

Linked b. Anthracis with disease. Looked at anthrax in mice

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14
Q

How many species are there in bacillus genus and nested genera

A

266 species

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15
Q

Where is bacillus cereus most commonly found

A

Ubiquitous

Typical soil and dust

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16
Q

Name two types of food b.cerus is associated with and why

A

Rice (associated starchy foods)
Herbs and spices
Dry foods e.g. Pot noodle

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17
Q

What are the two distinct foodborne intoxications of bacillus cereus

A

Emetic - vomiting
Diarrhoea

( different toxins)

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18
Q

Describe the incubation form and duration of EMETIC b.cereus and explain why it is this length

A

Onset 1-6 hours (short incubation)
Duration - up to 24 hours

Preformed toxin all have to do is eat - short incubation, as physical toxin clear form gut quicker henc 24 hr

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19
Q

What is the emetic toxin produced by b.cereus and what are key characteristics of this toxin

A

CEREULIDE

  • heat stable - hence cannot reheat
  • preformed
  • resistant to proteolytic cleavage - pepsin and trypsin in stomach will not denature toxin
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20
Q

What does the emetic toxin CEREULIDE do

A

Once in stomach directly activate vagal neural system and lead to release of SEROTONIN (activate serotonin receptor) - increased stimulation of enteric NS lead to nausea and vomiting.

Gut has lots of neural connections - toxin attack this

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21
Q

Describe onset and duration of b.cereus diarrhoea form

A

Onset 8-16 hours

Duration 24 hours but has been seen to go on for 4-5 days

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22
Q

What is the pore forming complex of b.cereus diahorreal form made up of and why is it pore forming (shape)

A 
Haemolysin BL (Hbl)
Nonhaemolytic enterotoxin (Nhe) 
Cytotoxon K (Cytk)

Produced in intestine

BETA barrel confirmation THROUGH membrane so form a barrel hole in membrane - cell death. Lose structure of intestine wall so lose function - cannot absorb water so lose in faeces.

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23
Q

What is differnt about diahorreal toxin to emetic form

A

Emetic - heat stabile, preformed

Diahorreal - heat LABILE (sensitive to gut acids and heat - if reheat this then safe as not heat stable).
Organism produce toxin in gut (organism must be live in food and eaten rather than toxin eaten) - not preformed like emetic form.

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24
Q

What conc of b.cereus required for symptoms

A

10^5 cfu g^-1

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25
Q

Above what degree is food safe to be kept

A

63 degrees

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26
Q

What risk factor is there for b.cereus

A

Contaminated foods subject to inadequate temp control and storage following cooking

27
Q

Why is it believed b.cereus is underreported

A

Rapid onset of symptoms
SHORT TERM DIARRHOEAL disease - unlikely
Big outbreaks noted but otherwise not likely

28
Q

What agar is used for laboratory diagnosis

A

b.cereus selective agar
MYP (mannitol yolk agar)
Egg yolk emulsion - look for lecithinase action (hydrolysis of lecithin)

Also bacillus cannot use mannitol so keep pH indicator a blue (bromothymol blue)

Polymixin B - inhibit gram negatives

29
Q

What colourful agar can be used for b.cereus diagnosis

A

Brilliance b.cereus agar

Chromogenic substrate
5-broom-4-chloro-3-indoxyl-B(beta)-glycopyranoside converted via beta glucosidase to give blue green colonies

30
Q

What are treatments and prevention for b.cereus

A

SELF LIMITING

Prevent via adequate cooking, cooling and storage of food

31
Q

What is interesting about presentation of b.cereus

A

If 100 people had same organism at same place present differently
Depend on age, health, whether taking other drugs affecting pH of stomach

Our relationship with organism is unique to our immune system - previous exposure etc

32
Q

What did rob koch grow B anthracis on

A

In sheep eyeballs - no agar in 1877

33
Q

Is b.anthracis gram positive or negative

A

Gram positive

34
Q

Is b.anthracis an aerobic sporeformer or anaerobic sporeformer

A

Aerobic sporeformer

35
Q

Where are the spores of b.anthracis located

A

Central/oval

36
Q

What is the size of b.anthracis

A

3-5um long (BIG)

37
Q

What do b.anthracis cells look like under a microscope

A

Square ended cells

38
Q

What flagella does b.cereus have and what type of colonies does it make

A

Peritchricous and form rhizoids colonies

39
Q

In 1887 what organism was classed by Koch as first bacterium capable of causing disease

A

b.anthracis

40
Q

What is schedule 5

A

Antiterrorism bill for microbial agents could be used as for terrorism. Even c perf on there

41
Q

What species does b.anthracis primarily affect

A

ZOONOSIS

Primarily disease of domesticated and wild animals - herbivores

42
Q

What are 3 main presentations in humans

A

1- cutaneous (skin)
2- inhalation into lungs
3- GI (eat spore or toxin in food)

43
Q

Which type of anthrax cause 95% of anthrax but is still rare

A

Cutaneous anthrax

44
Q

Which country is b.anthracis seen hugely

A

NZ and Australia

45
Q

How does cutaneous anthrax enter

A

Via minor skin abrasions in hands, arms, neck

46
Q

What does b.anthracis cutaneous develop into

A

Painless necrotic ulcer (lesion)

Dissemination occur which lead to septicaemia

47
Q

How many % of case die if untreated

A

5%

48
Q

Which form of anthrax is most ‘weaponised’ for dirty bomb

A

Inhalation anthrax

49
Q

What is infectious dose of b.anthracis

A

Approx 10,000 to 20,0000 spores

50
Q

What are the symptoms of b.anthracis inhalation

A

General flu like symptoms - respiratory difficulty

Dissemination in lymphatic system - shock (2-6 days)

51
Q

If untreated/delayed what percentage is fatal for inhaled b.anthracis

A

95%

52
Q

What is Gi anthrax associated with

A

Contaminated undercooked meat

53
Q

Where does gi anthrax enter

A

Intestinal mucosa (similar mechanism to cutaneous)

54
Q

What are primary sumoptoms of gi anthrax

A

Severe diarhoea
Vomit blood

Dissemination in blood - septicaemia and toxaemia

Used to get in via food industry

55
Q

What is fatality percentage of gi anthrax

A

65%

56
Q

When was largest most recent outbreak of injection anthrax

A

2009-2010 contaminated heroin

Spores withstand process before injected - germinate inside

7 people in UK died from it

57
Q

What feature of b.anthracis is used to attach and evade immune system

A

Use capsule.( glycocalix) slime later around cell and protect from environmental extremes( prevent phagocytosis )

Capsule made of Poly-D-Glutamate polypeptide capsule. Indian Ink doesnt stain capsule. Flourescent show capsule can be thicker than organism

58
Q

What toxins does b.anthracis release and what do they together bring about

A 
Protective antigen (PA) 
Edema Factor (EF) 
Lethal Factor (LF)

BRING ABOUT HYPOXIA, FLUID RETENTION AND NECROSIS (BLACK LESION)

59
Q

PA has two subunits a and B. Which is active and which binds

A

A - active

B - binding (Protective antigen PA)

60
Q

Describe mechanism of action for toxins

A

1- binding subunit of PA (B subunit) bind to ATR (anthrax toxin receptor)
2- furin (protease) cleave off a subunit to activate PA toxin
3- cause PA to form into heptomer (7 protein ring) with 6 other PA
4- as PAs come together drag membrane with them to form membrane raft which screws up membrane
5- 7 tail ends together form receptor for either EF or /and LF (toxins)
6- PA receptor get endocytosed dragging with it either EF or LF and once in endosome EF or LF dissoiate from AP
7- EITHER EF can interact with cAMP to get water retention or get LF with MAPK to get necrosis and hypoxia (cell death)

61
Q

When was last case of b.anthracis

A

2008

62
Q

What musical instrument release toxin and why

A

Animal hyde on drums not cured properly.- liberate toxins and spores of anthrax into air

63
Q

How do you diagnose b.anthracis in lab

A

Gram stain blood smear

Culture on blood agar
Non haemolytic
Ground glass colonies - medusa head

64
Q

What treatment and prevention is available

A

Antibiotics - ciprofloxacin (but need to know anthrax early on for good survival rates)

Prevention - avoid contact with animals, Iv drug use

Vaccine - BioThrax have AVA - anthrax vaccine absorbed against all 3 types of anthrax

Can use prophylactic antibiotics for those potentially exposed individuals

MICROBIOLOGY II (9 decks)

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