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Bacteriology > Neurotoxic Clostridia > Flashcards

Neurotoxic Clostridia Flashcards

1
Q

How many species of Clostridium are there and how many are pathogenic?

A

200 species, 20 being pathogenic

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2
Q

What are some general characteristics of Clostridium spp?

A

large motile gram-positive rods, produce endospores, fastidious anaerobes, catalase and oxidase-negative, ferment carbohydrates and proteins

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3
Q

How are Clostridium spp divided?

A

neurotoxigenic, enterotoxigenic, histotoxic

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4
Q

What is the habitat of Clostridium spp?

A

soil, freshwater or marine sediments, normal flora of intestines, sequestered as endospores in muscle and liver, animal feces

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5
Q

How are Clostridium spp transmitted?

A

ingestion of spores, wound contamination

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6
Q

What is the protocol for specimen collection for Clostridium spp?

A

must be taken from live or recently dead animals, collect samples from blocks of tissue or fluids, place in anaerobic transport media and culture promptly

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7
Q

What are the cultural requirements for Clostridium spp?

A

media should be freshly prepared or pre-reduced to ensure the absence of oxygen, incubate in anaerobic jar containing hydrogen supplemented with 5-10% carbon dioxide

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8
Q

What media is used for the culture of Clostridium spp?

A

blood agar enriched with yeast extract, vit K, and hemin, cooked meat medium

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9
Q

What methods are used for the detection and differentiation of clostridia?

A

limited colony morphology, PCR, fluorescent antibody techniques, commercial biochemical kits, ELISA to detect toxins

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10
Q

What are the main virulence factors of clostridia?

A

production of toxins

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11
Q

What species of Clostridium are neurotoxigenic?

A

C. tetani and C. botulinum

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12
Q

What are some general characteristics of C. tetani?

A

gram-positive straight and slender rods, anaerobic, spherical terminal endospores with drumstick appearance

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13
Q

What disease is associated with C. tetani?

A

tetanus

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14
Q

How is tetanus transmitted?

A

spores originating from soil or feces contaminating wounds

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15
Q

What are some common sources of infection of tetanus?

A

nail wounds in horses, castration and docking wounds in goats/sheep, castration, dehorning, and nose-ringing in cows, contaminated umbilical tissues in young animals

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16
Q

What are the virulence factors of C. tetani?

A

tetanospasmin or neurotoxin, tetanolysin

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17
Q

What is the pathogenesis of tetanus?

A

anaerobic conditions and wound contamination -> spores germinate -> bacteria start producing tetanospasmin in 4-8 hours -> binds ganglioside receptors on neurons -> blocks release of inhibitory NTs -> continuous stimulation by excitatory NTs -> spastic paralysis and tetanus

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18
Q

What does tetanolysin do in terms of pathogenesis of tetanus?

A

enhances pathogenesis by increasing permeability of cytoplasmic membrane

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19
Q

What is the incubation period for tetanus?

A

5-10 days up to 3 weeks

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20
Q

Why are the clinical signs delayed in latent tetanus?

A

due to wound healing

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21
Q

What does the nature and severity of tetanus depend on?

A

anatomical site of replicating bacteria and the amount of toxin produced

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22
Q

What species are most susceptible to tetanus?

A

horses* > humans > mice > rabbits > dogs > cats > chickens > cattle* > sheep > goats > pigs

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23
Q

What clinical signs are associated with localized (ascending) tetanus?

A

stiffness and spasm of muscles close to injury due to toxin on local nerve endings

24
Q

What clinical signs are associated with generalized (descending) tetanus?

A

stiff gait and “saw-horse” stance, lockjaw, mild tactile/auditory stimuli can precipitate seizures of muscle, altered heart and respiratory rates, dysphagia and prolapse of 3rd eyelid

25
Q

What is the tetanic triad in humans?

A

trimius (lock jaw), risus sadonicus (grimace), opisthotonus (arched back)

26
Q

How do you diagnose tetanus?

A

history and clinical signs, gram-stained smears, anaerobic culture from wound tissue, PCR, toxin assays

27
Q

How do you treat tetanus?

A

antitoxin, toxoid, penicillin, wound debridement

28
Q

How do you control tetanus?

A

routinely vaccinate with tetanus toxoid, antitoxin

29
Q

What are some general characteristics of C. botulinum?

A

gram-positive, straight/slightly curved, motile, oval sub-terminal endospores with tennis racquet appearance

30
Q

What disease is associated with C. botulinum?

A

botulism

31
Q

How is botulism transmitted?

A

ingestion of pre-formed toxin (intoxication) or spores that germinate to release toxin

32
Q

In what species is botulism outbreak common in?

A

waterfowl, cattle, horses, sheep, mink, poultry, farmed fish

33
Q

What species are relatively resistant to botulism?

A

pigs and dogs. rare in cats

34
Q

What are some predisposing factors of botulism in animals?

A

contaminated feed, dead rodents/carcasses, decaying plant/animal matter, contaminated poultry litter and bone chewing, warm moist decaying flesh (low O2)

35
Q

What are some virulence factors of C. botulinum?

A

BoNT (botulinum neurotoxin; 8 types)

36
Q

How is BoNT of C. botulinum inactivated?

A

by boiling for up to 20 minutes

37
Q

What types of BoNT are of major significance?

A

Type C and D

38
Q

What are some sources of type C BoNT?

A

dead invertebrates, maggots, rotting vegetation and carcasses of poultry (susc. to waterfowl, poultry), ensiled poultry litter, poor quality hay or silage contaminated with rodent carcasses (susc. to cattle, sheep, horses), meat, especially poultry carcasses (susc. to dogs, mink)

39
Q

What are some source of type D BoNT?

A

carcasses and bones (susc. to cattle and sheep), fish (susc. to fish eating birds and humans)

40
Q

What conditions are associated with type C alpha BoNT?

A

limberneck/western duck sickness in waterfowl and swans

41
Q

What conditions are associated with type C beta BoNT?

A

forage poisoning in cattle, horses, and dogs

42
Q

What conditions are associated with type D BoNT?

A

Lamsiekte in cattle and sheep from eating contaminated bones

43
Q

What condition is associated with toxico-infectious botulism?

A

shaker foal syndrome

44
Q

What is the pathogenesis of botulism?

A

botulinum neurotoxin enter bloodstream -> binds to peripheral cholinergic nerve endings -> blocks motor nerve endings -> inhibits release of NTs (ACh) -> descending flaccid paralysis starting from cranial nerves

45
Q

What is the incubation period for botulism?

A

3-17 days, average 2-6 days

46
Q

What are some of the clinical signs of botulism?

A

incoordination, dilated pupils, decreased salivation, dysphagia, progressive flaccid paralysis, head turned to flank in cattle, paralysis of respiratory muscles, death within days

47
Q

What do low phosphorus levels in cows lead to?

A

chewing on dead carcasses leading to ingestion of toxin and botulism

48
Q

What are some ways in which horses acquire botulism?

A

consumption of toxin in contaminated feed and water, contamination of wounds

49
Q

How do you diagnose botulism?

A

history and clinical signs, toxin assays, toxin neutralization, ELISA, PCR, MLST

50
Q

How do you treat botulism?

A

not usually successful, polyvalent antitoxin to neutralize unbound toxin in early stage, tetraethylamide and guanidine hydrochloride IV, ruminal or stomach lavage, fluid and nutritional supportive care

51
Q

How do you control botulism?

A

vaccinate farm animals routinely with toxoid. bivalent vaccines to protect against types C and D. good feed quality and avoiding contamination. burn and properly dispose of dead carcasses

52
Q

What are the options for vaccination against botulism?

A

short acting: 2 doses 4-6 weeks apart then annually. long acting: single dose and booster every 1-3 years

53
Q

T/F: clostridia are gram positive

A

TRUE

54
Q

T/F: clostridia are not capable of forming spores

A

FALSE

55
Q

A dog present with lock jaw, stiff gait, and seizures. What is the name of the toxin which is responsible for these clinical signs? a) hemolysin b) epsilon c) tetanolysin d) tetanospasmin e) botulinum

A

d) tetanospasmin

56
Q

T/F: botulinum toxin causes FLACCID paralysis

A

TRUE

Bacteriology (26 decks)

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