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
 
*Primary or secondary infections following viral infection
 
*Neonatal septicaemia related to maternal genital tract infection
 
*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
 
 
 
 
 
===[[Respiratory Bacterial Infections - Pathology#Strangles|Strangles]]===
 
 
 
*Epidemiology
 
**[[Respiratory Bacterial Infections - Pathology#Strangles|Strangles]] is a 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
 
**Transmitted via purulent exudate discharging from upper respiratory tract or from lymph nodes
 
**Chronic, carrier state can occur with bacteria im the guttural pouch
 
**A mild, atypical form can occur
 
**''S. equi'' shed for 4 weeks beyond clinical resolution
 
 
 
*Clinical signs
 
**Incubation period 3 to 6 days
 
**Fever, depression, anorexia
 
**Purulent nasal discharge
 
**Swollen, painful regional lymph nodes, especially submandibular
 
**Abscessation and rupture of lymph nodes
 
**Guttural pouch empyema
 
**100% morbidity; 5% mortality
 
**Death can occur from pneumonia, breathing difficulties from swollen lymph nodes or [[Muscles Degenerative - Pathology#Ischaemia|purpura haemorrhagica]](an immune-mediated disease)
 
**Bastard strangle may occasionally occur, with abscessaation in many organs of the body
 
 
 
*Diagnosis
 
**Clinical signs and history
 
**Mucoid colonies with beta-haemolysis
 
**Sugar fermentation allows differentiation of ''S. equi'' from ''S. zooepidemicus'' and ''S. equisimilis''
 
**PCR to detect asymptomatic carriers
 
 
 
*Treatment and control
 
**Penicillin administration to in-contact animals
 
**Isolation of affected animals
 
**Quaranteen in-coming animals
 
**Avoid overcrowding and mixing different age groups
 
**Disinfection of equipment
 
 
 
 
 
===''Streptococcus suis''===
 
 
 
*Meningitis, arthritis, septicaemia and [[Respiratory Bacterial Infections - Pathology#Streptococcal pneumonia|pneumonia]] of pigs
 
*Sporadic cases of endocarditis, neonatal deaths and abortion
 
*Carried in tonsils of carrier pigs
 
*Outbreaks occur in intensively-reared herds with poor hygiene
 
*Carrier sows infect litters causing neonatal deaths
 
*Meningitis with fever, tremors, incoordination, opisthotonos and convulsions
 
*Treatment with penicillin; prophylactic long-acting penicillin for sows and piglets
 
 
 
 
 
===Bovine streptococcal mastitis===
 
 
 
*''S. agalactiae, S. dysgalactiae'' and ''S. uberis'' primarily cause mastitis
 
*Also ''S. pyogenes, S. zooepidemicus'' and ''Enterococcus faecalis'' can be involved
 
*''S. agalactiae colonises milk ducts causing persistent infections with acute outbreaks
 
*''S. dysgalactiae'' found in the oral cavity and on the skin of the udder causes acute mastitis
 
*''S. uberis'' inhabits normal skin, tonsils and vaginal mucosa, and causes mastitis without systemic signs
 
*Cause inflammation of mammary tissue and clots form in milk
 
*Milk samples are cultured on blood agar, Edward's medium and MacConkey agar for 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
 
 
 
 
 
 
 
 
 
 
 
 
 
*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]]
 
 
 
 
 
*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 [[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