Category:Streptococcus species

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Overview

  • Cause suppurative infections in many different animals
  • Cause abscess formation and septicaemia
  • Cause mastitis, metritis, polyarthritis, meningitis
  • Primary or secondary infections following viral infection
  • Neonatal septicaemia related to maternal genital tract infection
  • Haemolytic streptococci of Lancefield group C are common inhabitants of the equine nasopharynx
  • Streptococcus zooepidemicus and S. equisimilis are usually non-pathogenic
  • Involved in peritonitis in pigs, pyothorax, osteomyelitis, catarrhal stomatitis
  • In infectious arthritis of sheep, arthritis in calves, arthritis in horses and arthritis in pigs
  • Often commensals on mucous membranes of upper respiratory and lower urogenital tract
  • Opportunistic infections


Characteristics

  • Gram positive cocci forming chains
  • Catalase negative, facultative anaerobes
  • Fastitidious - require enriched media such as blood or serum
  • Small haemolytic, translucent colonies, some mucoid
  • Catalase negative
  • Susceptible to desiccation


Identification

  • Beta haemolysis (complete with clear zones surrounding colonies)
  • Alpha haemolysis (partial with green zones surrounding colonies)
  • Lancefield grouping - serology based on group-specific polysaccharide in cell wall
  • Biochemical testing


Diagnosis

  • Swabs of pus or exudate cultured on blood agar and MacConkey agar
  • No growth on MacConkey except S. faecalis
  • PCR, Lancefield grouping and biochemical tests


Pathogensis and Pathogenicity

  • Beta-haemolytic strains more pathogenic than alpha-haemolytic strains
  • Virulence factors include streptolysins, hyaluronidase, DNase, streptokinase and proteases
  • S. pyogenes, S. pneumoniae and some strains of S. equi have polysaccharide capsules which are antiphagocytic
  • S. pyogenes and S. equi have antiphagocytic cell wall M proteins


Streptococcus equi subsp. equi


Streptococcus suis

Streptococcal mastitis - bovine



S. equisimilis

  • Found on skin and vagina of horses
  • Causes abscesses, endometritis and mastitis in horses
  • Suppurative conditions in pigs, cattle, dogs, birds


S. zooepidemicus

  • Colonises mucous membranes
  • Causes mastitis, pneumonia, sinusitis and navel infections in horses
  • S. zooepidemicus can cause similar signs to strangles in horses and may accompany COPD
  • Secondary invador after equine influenza
  • Colonises skin and mucous membranes of cattle, lambs, pigs and poultry and causes suppurative infections and septicaemia
  • Can cause vascular fragility, leading to haemorrhagic disease


Enterococcus faecalis

  • Colonises intestinal tract
  • Causes opportunistic suppurative infections in many species


S. canis

  • Found in vagina and anal mucosa of carnivores
  • Neonatal septicaemia, suppurative infections, toxic shock syndrome
  • In deep pyoderma and subcutaneous abscesses


S. pneumoniae

  • Found in upper respiratory tract of primates
  • Causes septicaemia, pneumonia and meningitis
  • Pneumonia in guinea-pigs and rats


S. porcinus

  • Submandibular lymphadenitis in pigs