97. General characteristics of diseases caused by clostridia, grouping of the diseases.

Question 1

Occurence?

Answer 1

• Worldwide,
• Tropical, subtropical area more frequent
• Different animal species,
• Sporadic

Question 2

Aetiology?

Answer 2

Aetiology

• Gram + rod, spore at end of bacterium or eccentric, Facultate pathogenic need PF
• Anaerobes (replicate only in the absence of O2), spore forming
• Biochemically active: fermentation of carbohydrates, produce extracellular enzymes & toxins(exotoxins)
• Habitat: Intestine soil (gut soil cycle: PO -> Gut -> shed in the enviroment
• Resistance: vegetative bacterium: average resistance; spores: very resistant (extremely resistant against heat)
• Virulence factors
• EC enzymes
• Toxins can turn to anatoxin/toxoid Æ for vaccine!

Question 3

Diagnosis?

Answer 3

Diagnosis

x Difficult:

• fast course,
• toxin effect (toxins do not cause morphological changes),
• PM lesions are frequently not typical

x Laboratory diagnostics

• o Detection of bacteria:
• microscopy,
• isolation,
• IF,
• PCR
• o Detection of antibodies:
• ELISA,
• blot,
• AGD (not informative b/c it is a fast disease ʹ similar to Anthrax)
• o Detection of toxins and extracellular enzymes: ELISA, mouse inoculation (toxin neutralisation test ʹ inoculate
• sample with hyperimmune serum can see which antiserum is inhibited),
• PCR (detect gene responsible for toxin production)

x Evaluation is difficult ʹ

• facultatative so detection alone is not enough!

Question 4

Treatment and prevention control?

Answer 4

Treatment:

• imited (fast course, toxic effects) ʹ
• effects caused by the toxin rather than by the bacterium so AB treatment is too late!

Prevention, control

• Prevention of predisposing effects:
• wounds,
• aseptic treatment,
• appropriate nutrition

Vaccines:

• inactivated culture (anaculture ʹ inactivated bacteria + inactivated toxins) or inactivated toxin
• (anatoxin, toxoid), 2 vaccinations then yearly
• o Excellent vaccines for the toxins
• x Hyperimmune serum