-
Several systems of classification have been employed. Based on growth characteristics, type of haemolysis and biochemical activities they can be divided into 6 principal categories.
|
Group
|
Examples
|
|
Pyogenic Streptococci
|
S. pneumoniae, S.pyogenes, S.equi, S. dysgalactiae
|
|
Oral Streptococci
|
S.salivarius
|
|
Enterococci
|
S.faecalis, S.avium, S. gallinarum
|
|
Lactic acid Streptococci
|
S.lactis
|
|
Anaerobic Streptococci
|
S. monbillorum
|
|
Other Streptococci
|
S.bovis, S.uberis, S.equi subsp zooepidemicus
|
-
The aerobic and facultative anaerobic streptococci are classified, based on their haemolytic properties.
-
Brown (1919) established this method by employing meat infusion peptone agar with 5% horse blood. He recognized three types of reactions.
-
alpha - haemolytic streptococci: They produce a greenish discolouration with partial haemolysis around the colonies.
-
The zone of lysis is small (1or2 mm wide), within which the unlysed erythrocytes are seen.
-
These ά - streptococci are generally commensals in the throat. Because of the distinctive green color, they produce; they are called as greening or viridans streptococci. Eg. S.pneumoniae
-
Beta haemolytic streptococci produces a sharply defined, clear, colourless zone of haemolysis, 2 or 4mm wide, within which the red cells are completely lysed.
-
Most of the pathogenic streptococci fall into the beta group and are called as the haemolytic streptococci.
-
Gamma or non-haemolytic streptococci produces no change in the medium.
-
The gamma streptococci includes the faecal streptococci ( S. faecalis) and related species. They are called the enterococcus or indifferent streptococci.
-
Another important way in which the beta haemolytic streptococci were classified by Rebecca lancefield (1933) was based on the nature of a carbohydrate (C) antigen on the cell wall. They are known as Lancefield groups, 19 of which have been identified so far and named by the capital letters A-U (without I and J)
|
Lancefield group
|
Species
|
Host
|
Disease
|
|
A
|
Streptococcus pyogenes
|
Humans
|
Scarlet fever , Septic sore throat, erysipelas, abscesses and rheumatic fever
|
|
B
|
S. agalactiae
|
Cattle, sheep and goats
|
Chronic mastitis
|
|
Human and dogs
|
Neonatal septicaemia
|
|
Cats
|
Kidney and uterine infections
|
|
C
|
S. dysgalactiae
|
Cattle
|
Acute mastitis
|
|
Lambs
|
Polyarthritis
|
|
S. dysgalactiae subsp. equismilis
|
Horse
|
Abscesses, endometritis and mastitis
|
|
S. equi. subsp. equi
|
Horse
|
Strangles , genital and suppurative conditions, Mastitis and purpura haemorrhagica
|
|
S. equi subsp. zooepidemicus
|
Horse
|
Mastitis, abortion, secondary Pneumonia and navel infections
|
|
Cattle
|
Metritis & Mastitis
|
|
Pigs
|
Septicaemia & arthritis in 1-3 wk old piglets
|
|
Poultry
|
Septicaemia & Vegetative Endocarditis
|
|
Lambs
|
Pericarditis and Pneumonia
|
|
D
|
Enterococcus faecalis
|
Many species
|
Opportunistic infections
|
|
S. equines and S. bovis
|
Many species
|
Opportunistic infections
|
|
E (P,U,V)
|
S. Porcinus
|
Pigs
|
Jowl abscesses and lymphadenitis
|
|
G
|
S. canis
|
Carnivores
|
Neonatal septicaemia, genital, skin and wound infections
|
|
Cattle
|
Occasional mastitis
|
|
N
|
Lactococcus lactis
|
Cattle
|
unknown
|
|
Q
|
Enterococcus avium
|
Many species
|
unknown
|
|
R
|
S.suis type 2
|
Pigs (4 to 6 months)
|
Meningitis and arthritis
|
|
S
|
S.suis type 1
|
Pigs (2 to 4wks old)
|
Meningitis and arthritis
|
|
Ungroupable
|
S.uberis
|
Cattle
|
Mastitis
|
|
S.pneumoniae
|
Guinea pigs, rats and primates
|
Pneumonia
|
-
Haemolytic streptococci of group A are known as S.pyogenes . These may be further subdivided into types based on the protein (M,T and R) antigens present on the cell wall.
-
The M protein is acid and heat labile and the T protein is acid labile and trypsin resistant.
-
Some of the Lancefield groups may be further subdivided by means of the agglutination test and designated by Arabic numbers-Griffith typing
|
Participants