Bacterial Pathogens: Staphylococci Quiz

Bacterial Pathogens: Staphylococci

• Learning Outcomes:
  • Know examples of common infections caused by different staphylococcus species.
  • Understand the economic and clinical importance of ruminant mastitis.
  • Know three of the most common mastitis pathogens.
  • Understand the pathogenesis of mastitis caused by S. aureus, including virulence factors and their mechanisms.
  • Know the host factors that influence outcomes of intramammary infections.
  • Understand methods for controlling mastitis.

Wide Array of Staphylococcal Infections in Animals

• Intramammary Infections (Mastitis):

  • Primarily affects cows, sheep, and goats.
  • Characterized by udder inflammation caused by pathogenic bacteria.
  • Often caused by Staphylococcus aureus.

• Wound Infections:

  • Include abscesses and pustules.
  • Various species of Staphylococcus act as opportunistic pathogens.
  • S. pseudintermedius is commonly associated with pyoderma in dogs.
  • Folliculitis can sometimes accompany pyoderma.
  • Ixodes ricinus ticks are a factor in infections following tick bites.

• Other Infections:

  • S. hyicus causes exudative epidermitis (greasy pig disease) in pigs, leading to highly contagious skin infections.
  • Staphylococcus species can affect joints, bones, and the urinary tract (e.g., cystitis) in various animals.
  • S. aureus, S. pseudintermedius, and other Staphylococcus species cause dermatitis, osteomyelitis, arthritis, and septicemia.

Mastitis - Intramammary Infection - Usually Staphylococcus aureus

• Infection Types:

  • Subclinical mastitis: No noticeable symptoms, but white blood cell counts are elevated.
  • Clinical mastitis: Noticeable symptoms of inflammation, swelling, pain, and clots in milk.
  • Peracute mastitis: Very severe, systemic inflammation, high fever, and death can occur.

• Economic Implications:

  • Mastitis costs UK farmers approximately £93 million per year.

Other Major Mastitis Pathogens

• Contagious: Staphylococcus aureus, Streptococcus agalactiae, and Streptococcus dysgalactiae.
• Environmental: Streptococcus uberis, Streptococcus faecalis, Escherichia coli, coagulase-negative staphylococci (Mycoplasma bovis) , and Corynebacterium bovis.

Bovine Mastitis Pathogenesis

• Staphylococcus aureus often colonize teats for extended periods.
• Teat duct colonization facilitated by feeding on milk as a nutrient source.
• Adherence to epithelial cells is a key step in pathogenesis.

S. aureus Virulence Factors

• Adherence:

  • S. aureus attaches to host proteins through microbial surface components recognizing adhesive matrix molecules (MSCRAMMs)
  • Binding to host proteins such as laminin and fibronectin promotes attachment.

• Avoiding Host Defenses:

  • Capsular polysaccharide: Capsule type 5 and 8 are associated with infections.
  • Staphylococcal protein A (SpA):
  • Binds to immunoglobulins, disrupts opsonization, and inhibits phagocytosis.
  • Superantigens: Stimulate T cells nonspecifically, resulting in excessive cytokine release.
  • Membrane damaging toxins: Include a-toxin, which damages cell membranes by forming pores. B-toxin, damaging membranes particularly rich in sphingomyelin and 8-toxin, a cytotoxin produced by most S. aureus strains.

Host Genetic Factors Affecting Bovine Mastitis

• Factors impacting susceptibility in various animal species: includes variables in in vitro phagocytosis ability, lactoferrin, lysozyme, and major histocompatibility complex.

Control and Treatment of Mastitis

• Milk hygiene (disinfecting equipment) is essential. Teat and udder washing is vital before milking.

Avian and Other Animal Infections

• Various Staphylococcus species cause different infections in other animals like poultry, dogs, cats. (mentioned in previous sections).

Antibiotic Resistance

• Methicillin-resistant Staphylococcus aureus (MRSA) are problematic in human and animal infections.

Test your knowledge on the different species of Staphylococcus and their role in animal infections, such as mastitis. This quiz covers examples of common infections, their economic impact, and methods for controlling mastitis. Dive deep into the pathogenesis and virulence factors of these pathogens.