Systematic Veterinary Bacteriology and Mycology

TOXINS AND VIRULENCE FACTORS

• It consists of capsule, Teichoic acid, which have antiphagocytic ability.

Exotoxins

• Hemolysin
  • Four antigenically distinct hemolysins causes hemolysis of erythrocytes. They are Alpha, Beta, delta and Epsilon toxin, which produce partial hemolysis (hot – cold hemolysis). The alpha toxin is the major toxin in gangrenous mastitis. It causes spasm of smooth muscle and is necrotizing and potentially lethal.
• Leukotoxin
  • It has the leukocidal activity and includes a and d toxins. By doing so, the organisms may spread more easily to other parts where they develop secondary lesions.
• Enterotoxin
  • It is seldom produced by animal strains. There are several antigenically distinct types of heat stable enterotoxins. They are not destroyed at 100°C for 80 minutes. They are responsible for food poisoning in man.
• Exfoliative or Dermonecrotoxin
  • This toxin causes necrosis of skin by exfoliation and intraepidermal seperation.
• Toxic shock syndrome toxin (TSST)
  • Induce excessive lymphokine production and results in tissue damage. Bovine and human strains of Sta. aureus produce TSST.

Extracellular enzymes

• Coagulase
  • On their ability to coagulate plasma they are classified as coagulase positive staph. (CPS) and coagulase negative staph. CPS are considered to be significant pathogens. They are resistant to heat. The coagulation of plasma produces a fibrin film on the surface of the organisms, which allows multiplying.
• Hyaluronidase
  • It hydrolyses hyaluronic acid, the mucoid ground substance of connective tissue.
• Nucleases
  • Deoxyribonucleases (DNAase) hydrolyze DNA and Ribonucleases hydrolyze RNA.
• Fibrinolysin
  • Fibrinolysin is commonly referred to as staphylokinase, is an activator of the plasma system leading to the breakdown of fibrin.
• Lipases and esterases - They hydrolyze lipids.
• Lysozyme - Hydrolyses the peptidoglycan in the cell wall of many bacteria