Microkalanjiyam

 

 Staphylococcus aureus

Posted By Admin    on 12-08-2021    Comments (10)

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 Streptococcus pneumoniae

Posted By Admin    on 31-03-2022    Comments (10)

STREPTOCOCCUS PNEUMONIAE (PNEUMOCOCCUS)
• Gram positive diplococcus ,
• lancet shaped or arranged in chains
• polysaccharide capsule – typing with antisera
• Pneumococci readily lysed by surface active agents which removes inhibitors of cell wall autolysis
• Pneumococci – normal inhabitants of upper respiratory tract (5 – 40 % of humans)
• Pneumococci causes pneumonia ,sinusitis,ottitis media,bronchitis ,bacteremia,meningitis and other infections.

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 Streptococcus pneumoniae

Posted By Admin    on 30-09-2023    Comments (10)

Gram positive diplococcus ,
lancet shaped or arranged in chains
polysaccharide capsule – typing with antisera
Pneumococci readily lysed by surface active agents which removes inhibitors of cell wall autolysis
Pneumococci – normal inhabitants of upper respiratory tract (5 – 40 % of humans)
Pneumococci causes pneumonia ,sinusitis,ottitis media,bronchitis ,bacteremia,meningitis and other infections.

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 Streptococcus pneumoniae

Posted By Admin    on 30-09-2023    Comments (10)

BILE SOLUBILITY TEST – Lysis of pneumococci occurs in a few minutes when ox bile (10%) or sodium deoxycholate (2%)  is added to a broth culture 

OPTOCHIN SUSCEPTIBILITY – growth of pneumococci is inhibited around the optochin disk.

These 2 features are used to differentiate it from other viridans streptococci

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 Streptococcus pneumoniae

Posted By Admin    on 30-09-2023    Comments (10)

ANTIGENIC STRUCTURE
Component structure – Pneumococcal cell wall has peptidoglycan and teichoic acid
Capsular polysaccharide (>90 types) – covalently bound to peptidoglycan and to cell wall polysaccharide – diffuses into media ,exudates and tissues (specific soluble substance)

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 Streptococcus pneumoniae

Posted By Admin    on 30-09-2023    Comments (10)

C –REACTIVE PROTEIN :
An abnormal protein (beta globulin) – precipitates with somatic  C antigen of Pneumocci appears in acute phase of sera ,disappears in convalescence.
It ia an acute phase substance produced in hepatocytes – its production stimulated by bacterial infections ,inflammations,malignancies and tissue destruction.
CRP testing by passive agglutination using latex particles coated with anti – CRP antibody is a routine diagnostic test.

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 Streptococcus pneumoniae

Posted By Admin    on 30-09-2023    Comments (10)

VIRULENCE FACTORS
Ig A1 protease : extracellular protease that specifically cleaves IgA1 in hinge region of upper respiratory tract.
Pneumolysin : intracellular membrane damaging toxin known as pneumolysin  (released by autolysis) inhibits neutrophil chemotaxis,phagocytosis and respiratory burst ,lymphocyte proliferation and immunoglobulin synthesis,immunogenic
Autolysin – activation leads to breaking of peptide cross linking of cell wall peptidoglycan  -lysis of bacteria  - release of large amounts of cell wall fragments  -massive inflammatory response – pneumococcal pneumonia and meningitis.
Tuftsin –naturally occurring tetrapeptide – secreted by spleen  -pneumococcal sepsis in congenital asplenia,traumatic removal ,functional impairment (eg homozygous sickle cell disease)


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 Streptococcus pneumoniae

Posted By Admin    on 30-09-2023    Comments (10)

40 – 70 % carriers of virulent pneumococci in normal respiratory  mucosa must possess great natural resistance to pneumococcus.
Viral and other respiratory tract infections that damage surface cells ,abnormal accumulation of mucus (eg allergy)- protect pneumococcus from phagocytosis, bronchial obstruction,respiratory tract injury due to irritants  disturb its mucociliary action.
Alcohol or drug intoxication  -depress phagocytic activity ,depress cough reflex  and facilitate aspiration of foreign material
Abnormal circulatory dynamics (eg pulmonary congestion ,heart failure)
Malnutrition,general debility ,sickle cell anaemia,hyposplenism,nephrosis or complement deficiency


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