Streptococcus

–  “The genes of SPE “A” and SPE ‘C’ are transmitted between the strains of streptococcus by bacteriophage° and stable production depends on lysogenic conversion”.

–  “The genes for SPE B are coded by chromosomes^Q“.(not plasmids)

• SPE A and SPE C’ are also called erythrogenic toxins as they are responsible _.for rash observed in patients with scarlatina.

–   They have superantigen activity which causes massive release of inflammatory gtokines from T lymphocytes causing fever, shock and tissue damage.

• Pyrogenic exotoxin A          Gene transmitted by /3 phase
• Pyrogenic extoxin B            Gene transmitted by chromosome
• Pyrogenic exotoxin C             Gene transmitted by fi phase

Strains with well marked capsules produce mucoid colonies. Streptococcus pyogenes can be typed based on surface proteins to M,T,R. M protein is most important of these. It act as a virulence factor by inhibiting phagocytosis. It is antigenic and antibody to this promotes phagocytosis of coccus.

.   Coagulase test is used to differentiate the different species of staphylococci (staph aureus, staph. epidermidis).

Ans. is ‘a’ i.e., Lancefield classification

Ans. is ‘d’ i.e., M protein

Virulence factors of str. pyogenes

Str. pyogenes forms several exotoxins and enzymes which contribute to its virulence, but M protein is the most important of these.

Ans. is D.) ‘a’ i.e., Streptolysin 0; ‘b’ i.e., Streptolysin S.

List of Streptococcal hemolysins:

• Streptolysin S
• Streptolysin O
• Pneumolysin
• β-Haemolysin/cytolysin
• Intermedilysin.

List of Streptococcal Toxins:

• Streptolysin O

• 1. Oxygen and heat labile
• 2. Antigenic
• 3. ASO titres used in retrospective diagnosis Rheumatic fever (ASO titres > 200 significant)
• 4. ASO titres – low after skin infection

• Streptolysin S

• 1. Oxygen stable, soluble in serum
• 2. Not antigenic

• Pyrogenic exotoxin/Erythrogenic/Dick/Scarlational toxin – Superantigen

• 1. Associated with streptococcal toxic shock syndrome Et scarlet fever
• 2. Dick test – intradermal test to identify children susceptible to scarlet fever
• 3. Schultz-Charlton reaction – diagnostic test for scarlet fever

• Streptokinase(Fibrinolysin)

• 1. Facilitates spread of infection
• 2. Used in retrospective diagnosis

• DNAase or Streptodornase

• 1. Liquefies thick pus and responsible for thin serous character of streptococcal exudates Anti-DNAse,
• Anti-hyaluronidase: retrospective diagnosis of pyoderma & glomerulonephritis

• Hyaluranidase – Spreading factor

Ans. is `c i.e.  Group ‘B’ causes neonatal meningitis

• Lancefield classification is based on carbohydrate ‘C’ antigen not on M protein.
• Besides Str. pyogenes, streptococci belonging to group B, C, D, F, G and rarely H, K, 0 and R may also cause human infections.
• Group B streptococcus is the single most common cause of neonatal meningitis.
• Group C streptococci are part of normal flora of throat (not of vaginal flora)
• Group D streptococci ie enterococci can cause urinary tract infection.

Ans. is ‘d’ i.e., D

Among streptococci, enterococcus (group D streptococcus) is heat resistant.

Ans. is ‘d’ i.e., Bile solubility

After 18 hrs of incubation both Str. viridans and pneumococcus produce similar colonies with alpha hemolysis but on further incubation the colonies of pneumococcus become flat with raised edges and central umbonation, so that concentric rings are seen on the surface when viewed from above (draughtsman or carrom coin appearance).

Differentiation between Stn pneumoniae and Sir. viridans

Ans. is ‘a’ i.e., Bile salt solubility

.  Pneumococcus is bile soluble, while streptococcus is insoluble.

• Pneumococcus ferments inulin, streptococcus does not.

Ans. is ‘d’ i.e., Cell wall carbohydrate 

Ans. is ‘d’ i.e., Epidermolysis bullae 

Ans. is ‘a’ i.e., Group C causes no human infection 

Ans. is ‘d’ i.e., Streptococcus type A

Ans. is ‘d’ i.e., Caused by streptococcus 

Ans. is ‘b’ i.e., Streptococcus 

“The most common organisms associated with cellulitis are group A streptococci and S. aureus.”- Schwartz

Ans. is ‘a’ i.e., Streptococcus 

Ans. Streptococcus

Ans. Streptococcus

Ans. Klebsiella

Ans. is ‘a’ i.e., Streptococcus

Ans. is ‘b’ i.e., Group B streptococcus