Difference between revisions of "Streptococci"

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#REDIRECT[[: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
 
*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 [[Respiratory Bacterial Infections - Pathology#Strangles|strangles]] with [[Nasal Cavity Inflammatory - Pathology#Strangles|rhinitis]], [[Nasopharynx Inflammatory - Pathology|pharyngitis]], lymphadenitis, [[Muscles Inflammatory - Pathology#Abscesses|myositis]]
 
*''S. equi'' may be involved in [[Bacterial skin infections - Pathology#Systemic bacterial infections|cutaneous lesions]]
 
[[Respiratory Bacterial Infections - Pathology#In Horses|URT inflammation in horses]]
 
 
 
* [[Peritoneal Cavity Inflammatory - Pathology#In pigs|peritonitis in pigs]]
 
 
 
*''S. zooepidemicus'' can cause similar signs to [[Respiratory Bacterial Infections - Pathology#Strangles|strangles in horses]], may accompany [[Bronchi and Bronchioles Inflammatory - Pathology#Chronic obstructive pulmonary disease (COPD)|COPD]]
 
 
 
*May cause [[Paranasal Sinuses Inflammatory - Pathology|sinusitis]] in horses
 
 
 
* Can cause vascular fragility, leading to [[General Pathology - Haemostasis#Haemorrhagic Disease Due To Vascular Fragility|haemorrhagic disease]].
 
*Secondary invadors after [[Respiratory Viral Infections - Pathology#Equine influenza|Equine influenza]]
 
*''S. suis'' in [[Respiratory Bacterial Infections - Pathology#Streptococcal pneumonia|pneumonia]] of pigs
 
 
 
*In [[Pleural Cavity & Membranes Inflammatory - Pathology#Pyothorax (Thoracic empyema)|pyothorax]]
 
* In [[Bones Inflammatory - Pathology#Osteomyelitis|osteomyelitis]]
 
 
 
*In infectious [[Joints Inflammatory - Pathology#In Sheep|arthritis of sheep]], [[Joints Inflammatory - Pathology#In Cattle|arthritis in calves]], [[Joints Inflammatory - Pathology#In Horses|arthritis in horses]] and [[Joints Inflammatory - Pathology#In Pigs|arthritis in pigs]]
 
 
 
*In horses sometimes [[Muscles Degenerative - Pathology#Ischaemia|purpura haemorrhagica]] follows, especially during recovery from [[Respiratory Bacterial Infections - Pathology#Strangles|strangles]]
 
*In [[Cavity & Gingiva - Pathology#Catarrhal Stomatitis|catarrhal stomatitis]]
 
 
 
*In [[Bacterial skin infections - Pathology#Deep pyoderma|deep pyoderma]] and subcutaneous abscesses
 

Latest revision as of 10:18, 17 May 2010