Streptococcus These are Gram positive cocci arranged in

Streptococcus ØThese are Gram positive cocci arranged in chains. ØSome of them are normal

CLASSIFICATION Streptococci O 2 Requirement Aerobic and FA 1. Alpha haemolytic ( Viridance )

S. pyogenes Morphology Ø Cocci measuring about 0. 5 - 1. 0 µm in

Cultural characters: Ø It is a aerobic and facultative anaerobic bacteria, optimum temp is

Biochemical reactions 1. Catalase test : Negative 2. Bacitracin : Sensitive 3. Bile solubility

1. Toxin production Ø Produces two types of haemolysins 1. Haemolysin “S” 2. Haemolysin

Pathogenesis Can cause : 1. Pyogenic infections. 2. Non pyogenic sequelae. 1. Pyogenic infections:

B. Deep infections 1. Pharyngitis. 2. Tonsillitis. 3. Septicaemia. 4. Osteomyelitis. 5. Abscesses in

Non pyogenic complications 1. Acute rheumatic fever. 2. Acute glomerulonephritis. Lab Diagnosis A. Pyogenic

B. Non pyogenic infections: By serological reaction for antibody demonstration by Antistreptolysin “O” test

Viridans streptococci Ø This group produces alpha haemolysis on blood agar. Ø These are

Predisposing factors: 1. Valvular disease of the heart. 2. Congenital heart disease. 3. Cardiac

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Streptococcus ØThese are Gram positive cocci arranged in chains. ØSome of them are normal flora of human.

CLASSIFICATION Streptococci O 2 Requirement Aerobic and FA 1. Alpha haemolytic ( Viridance ) Obligatory 2. Beta haemolytic Serological 20 Lancefield groups ( A to V except I and J ) Grifith types ( 80 Types ) ( 1 to 80 ) 3. Gamma haemolytic ( Enterococcus gp)

S. pyogenes Morphology Ø Cocci measuring about 0. 5 - 1. 0 µm in diameter and are arranged in chains. They are Gram positive.

Cultural characters: Ø It is a aerobic and facultative anaerobic bacteria, optimum temp is 37°C. Ø Growth occurs only in the madia containing blood, serum or fermentable sugars. Media 1. Blood agar. 2. Crystal violet blood agar. 3. Glocose broth.

Biochemical reactions 1. Catalase test : Negative 2. Bacitracin : Sensitive 3. Bile solubility : Not soluble Resistance Ø It is a delicate organism can be inactivated by heat, antiseptics. Ø Sensitive to most of the antibiotics, no drug resistance is seen.

1. Toxin production Ø Produces two types of haemolysins 1. Haemolysin “S” 2. Haemolysin “O” Ø Pyrogenic exotoxin ( Erythrogenic toxin ) 2. Enzymes 1. Streptokinase 2. Hyalurunidase 3. DNAases

Pathogenesis Can cause : 1. Pyogenic infections. 2. Non pyogenic sequelae. 1. Pyogenic infections: A. Skin infections: Two types, Erysipelas and Inpetigo.

B. Deep infections 1. Pharyngitis. 2. Tonsillitis. 3. Septicaemia. 4. Osteomyelitis. 5. Abscesses in the internal organs.

Non pyogenic complications 1. Acute rheumatic fever. 2. Acute glomerulonephritis. Lab Diagnosis A. Pyogenic infections: Swab, Pus, Blood etc 1. Gram’s staining. 2. Culture 3. Biochemical reactions

B. Non pyogenic infections: By serological reaction for antibody demonstration by Antistreptolysin “O” test (ASO) Titre > 200 IU/ml is significant. Treatment : Penicillin G is the drug of choice. Prophylaxis: Ø Ø Indicated only in the prevention of rheumatic fever. By giving long period Penicillin G to prevent re-infections.

Viridans streptococci Ø This group produces alpha haemolysis on blood agar. Ø These are known as viridans ( Viridis meaning green ) streptococci due to greenish discolouration on blood agar. Ø They are commensals of mouth and upper respiratory tract. Imp species: S. salivarius. S. mutans. S. milleri.

Predisposing factors: 1. Valvular disease of the heart. 2. Congenital heart disease. 3. Cardiac surgery. 4. Dental procedure. They may cause transient bacteraemia and get implanted on damaged or prosthetic valves or in a congenitally diseased heart and grow to form vegetations.

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