Difference between revisions of "Streptococci"
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*Cause suppurative infections in many different animals | *Cause suppurative infections in many different animals | ||
| + | *Cause abscess formation and septicaemia | ||
*Cause mastitis, metritis, polyarthritis, meningitis | *Cause mastitis, metritis, polyarthritis, meningitis | ||
| + | *Often commensals on mucous membranes of upper respiratory and lower urogenital tract | ||
| + | *Opportunistic infections | ||
| Line 20: | Line 23: | ||
*Catalase negative, facultative anaerobes | *Catalase negative, facultative anaerobes | ||
*Fastitidious - require enriched media such as blood or serum | *Fastitidious - require enriched media such as blood or serum | ||
| − | *Small haemolytic, translucent colonies | + | *Small haemolytic, translucent colonies, some mucoid |
*Catalase negative | *Catalase negative | ||
*Susceptible to desiccation | *Susceptible to desiccation | ||
| − | |||
| Line 34: | Line 36: | ||
| − | ===Pathogenicity=== | + | ===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 | ||
===Clinical infections=== | ===Clinical infections=== | ||
| + | *Primary or secondary infections following viral infection | ||
| + | *Neonatal septicaemia related to maternal genital tract infection | ||
| + | *Strangles | ||
| + | **Highly infectious disease of horses caused by ''Streptococcus equi'' subsp. ''equi'' | ||
| + | **Upper respiratory tract disease with fever and abscessation of regional lymph nodes | ||
| + | **Outbreaks in groups of young horses | ||
| + | ** | ||
===Diagnosis=== | ===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 | ||
Revision as of 12:05, 29 December 2008
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Overview
- Cause suppurative infections in many different animals
- Cause abscess formation and septicaemia
- Cause mastitis, metritis, polyarthritis, meningitis
- 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
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
Clinical infections
- Primary or secondary infections following viral infection
- Neonatal septicaemia related to maternal genital tract infection
- Strangles
- Highly infectious disease of horses caused by Streptococcus equi subsp. equi
- Upper respiratory tract disease with fever and abscessation of regional lymph nodes
- Outbreaks in groups of young horses
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
Treatment
Control
- Haemolytic streptococci of Lancefield group C are common inhabitants of the equine nasopharynx
- Streptococcus zooepidemicus and S. equisimilis are usually non-pathogenic
- S. equi is more pathogenic and is the cause of strangles with rhinitis, pharyngitis, lymphadenitis, myositis
- S. equi may be involved in cutaneous lesions
- S. zooepidemicus can cause similar signs to strangles in horses, may accompany COPD
- May cause sinusitis in horses
- Can cause vascular fragility, leading to haemorrhagic disease.
- Secondary invadors after Equine influenza
- S. suis in pneumonia of pigs
- In pyothorax
- In osteomyelitis
- In infectious arthritis of sheep, arthritis in calves, arthritis in horses and arthritis in pigs
- In horses sometimes purpura haemorrhagica follows, especially during recovery from strangles
- In catarrhal stomatitis
- In deep pyoderma and subcutaneous abscesses