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BACTERIOLOGY > 12 – Bacillus > Flashcards

12 – Bacillus Flashcards

1
Q

Microbial characteristics

A
  • vary of biocontainment levels
    o B. anthracis=level 3
  • large, spore forming, gram-positive rods
  • aerobic, facultative anaerobic
  • form large, irregular colonies
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2
Q

Natural host or habitat

A
  • Ubiquitous (found in environment, water, soil)
  • Spores survive for decades
    o Highly resistant to desiccation, heat, radiation and disinfectants
    o Can survive for decades (or longer!)
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3
Q

B. anthracis morphological characteristics

A
  • “medusa heads” on gram stain
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4
Q

Virulence factors

A
  • Virulent ones are encapsulated
  • Protective antigen
  • Edema toxin
  • Lethal toxin
  • *these 3 on own=inactive
  • Protective antigen
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5
Q

Protective antigen

A
  • Forms heptameric pores in cell wall
    o Edema factor (EF) or lethal factor(LF) then bind to enter cell and create toxins
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6
Q

Lethal factor (LF)

A
  • Inactivates MAPK kinases
  • Disrupts cell signalling=leading to apoptosis
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7
Q

Edema factor (EF)

A
  • Calmodulin dependent adenylate cyclase
  • Increased intracellular cAMP leads to edema
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8
Q

B. cereus: virulence factors

A
  • exotoxins which are responsible for gastroenteritis
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9
Q

B. thuringiensis (insect pathogens): virulence factors

A
  • crystal toxins (disruption of gut)
  • digestion of crystal liberates Cry toxin
  • used as a larvicide in mosquito control
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10
Q

B. subtilis virulence factors

A
  • largely non-pathogenic
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11
Q

Susceptibility ladder of species to B. anthracis

A
  • most: cattle, sheep, goats
  • intermediate: horses, humans
  • lowest: pigs, birds, carnivores
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12
Q

Why might some species be more resistant to B. anthracis?

A
  • Carnivores eat lots of dead animals
  • *lifestyle and dietary choices
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13
Q

B. anthracis (ruminants)

A
  • acquired by ingesting endospores
  • often seen when drought followed by heavy rainfall
  • sudden death
  • *if suspect, do NOT perform necropsy and call CFIA
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14
Q

B. anthracis (ruminants): sudden death

A
  • Incomplete rigor migor, splenomegaly
  • Failure to clot: if cut carcass=blood flows freely
  • **On exposure to oxygen, it will sporulate and are extremely resistant to disinfection
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15
Q

B. anthracis (horse)

A
  • Presents as acute intestinal disease
    o Colic, diarrhea, fever, depression
  • Localized lesions can be seen
    o Due to insect transmission
  • may see dependent edema (thorax, abdomen, prepuce, mammary gland)
  • followed by fatal septicemia
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16
Q

Anthrax outbreak in SK in 2006

A
  • ante-moretm: not really an pathognomic clinical signs
    o depression, SQ edema, skin lesions
  • post-mortem: dripping blood, failure to clot or darken blood)
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17
Q

B. anthracis (pigs and meat)

A
  • oral/pharyngeal lesions most common
    o ulceration at site of entry
    o regional lymphadenitis
    o ulcerative and haemorrhagic enteritis
18
Q

B. anthracis (carnivores)

A
  • rarely affected
  • when diseased, similar to pigs
  • septicemia with massive exposure
19
Q

B. anthracis (hippo)

A
  • disease recognized as animal die-offs
  • serious public health concern
    o exposure to or consumption of carcases associated with human disease
20
Q

4 distinct forms of B. anthracis in people

A
  1. Cutaneous (most common)
  2. Pulmonary
  3. Oropharyngeal
  4. Gastrointestinal
21
Q

Cutaneous form of B. anthracis (people)

A
  • Direct contact with infected animal tissues
  • Lesions develop 2-5 days post exposure
  • Mortality rate 10-20% if untreated
22
Q

Pulmonary form of B. anthracis (people)

A
  • Inhalation of endospores, phagocytosis in lungs
  • Lethal toxin kills macrophages
  • Hemorrhagic necrosis of mediastinum
  • 1-3 day incubation period
  • Mortality rate 80-90% if untreated
23
Q

Oropharyngeal and gastrointestinal forms of B. anthracis (people)

A
  • Associated with ingestion of spores or vegetative cells
  • GI form: 2-7 day incubation period, fever, nausea, bloody vomiting
  • Oropharyngeal form: cervical and oral pain and edema
  • *if sepsis untreated=DEATH
24
Q

B. cereus (humans)

A
  • Acute, self-limiting gastroenteritis
  • Emetic form
  • Long incubation food poisoning
  • *some strains grow at low temperature 4-7 degree C
25
Q

Emetic form of B. cereus

A
  • ingestion of cereulide toxin
  • 1-6hr following ingestion
  • Associated with rice, cream and milk products, pasta and infant formula
26
Q

Long incubation food poisoning

A
  • Ingestion of hemolysins
  • Watery diarrhea, nausea, tenesmus (straining to defecate)
  • Associated with meat, vegetables, cakes, sauces and dairy
27
Q

Paenibacillus larvae

A
  • Pathogen of honeybee larvae
  • Causes American foulbrood disease
  • Acts by multiplicity of mechanisms
  • Antibiotic and probiotics for prevention
  • Infection control is key
28
Q

Paenibacillus larvae acts by multiplicity of mechanisms

A
  • Chitin degrading enzymes
  • Toxins leading to intestinal epithelial cell death
  • S-layer proteins on cell surface, protect from insect immune system
29
Q

Specimens to collect

A
  • B. anthracis: do NOT perform necropsy
    o Collect blood from ea
    o If working in dusty environment, respiratory protection is ESSENTIAL
  • Non-anthracis species can be handled using standard precaution (milk, tissues from aborted fetuses)
30
Q

Sample handling

A
  • Do NOT freeze
31
Q

Lab ID: B. anthracis

A
  • MUST work in biosafety cabinet if suspect
  • Direct microscopy
  • Culture on blood agar
  • Non-hemolytic colonies
32
Q

Lab ID: non-antracis species

A
  • Culture
33
Q

Lab ID: blood from ear tip

A
  • Microscopy useful to see spores
    o Special staining (methylene blue) required
34
Q

B. anthracis zoonotic/interspecies transmission

A
  • Extremely difficult to get rid of from environment
    o Removal of top 20cm of soil
    o Disinfecting soil and equipment with FORMALIN
    o Burn or bury contaminated disposables along with carcasses
  • **PPE is critical
35
Q

Destroying spores in environment is very challenging

A
  • Ounce of prevention (not performing necropsies) is worth a pound of cure (formalin!)
36
Q

B. anthracis in beef cow example

A
  • Affected quarter was swollen, darkened and necrotic appearing
  • Milk was serosanguinous and watery
  • Classical chains of rod shaped bacteria seen in staining of milk
37
Q

Treatment of choice: B. anthracis

A
  • High DOSE penicillins or tetracyclines
38
Q

Drugs to avoid/intrinsic resistance: B. thuringiensis

A
  • Intrinsically resistant to penicillins
39
Q

Drugs to avoid/intrinsic resistance: B. anthracis

A
  • Resistant to 2nd and 3rd generation cephalosporins and trimethoprim + sulfamethoxazole
40
Q

Control measures

A
  • B. anthracis vaccination
  • Antimicrobial prophylaxis is some outbreak situations
  • Control the area (keep animal scavengers out)
  • Proper disposal of carcasses
  • Prevent additional contamination of environment

BACTERIOLOGY (19 decks)

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