Streptococcus pneumoniae

pneumoccoci

1. STREPTOCOCCUS PNEUMONIAE Dr . V S Vatkar Asso Prof Microbiology department D Y Patil Mwdical college, Kolhapur

2. INTRODUCTION Gram + ve Lanceolate shaped diplococci Bile soluble Optochin sensitive Specific polysaccharide capsule Normal inhabitant of URT, mainly causes pneumonia & otitis media in children Sinusitis , bronchitis, meningitis e tc First noticed by Pasteur in 1881

3. morphology Small, lanceolate shaped (one end pointed & other end flat) Arranged in pairs Capsulated : encloses each pair, usually seen in fresh sample, lost during repeated subculture, well demonstrated in India ink preparation Non motile, non- sporing Easily stained with aniline dyes, gram + ve

4. Gram Stain

5. Cultural characteristics Aerobes & facultative anaerobes Optimum temp : 37 0 C, pH : 7.8 Growth improves in 5-10 % CO2 Blood Agar : small dome shaped colonies with green discoloration ( α hemolysis) , further incubation colonies become flat with raised edges & central umbonation ( Draughtsman or Carom Coin Appearance) Some strains produce abundant capsular material : large mucoid colonies are seen

6. Colonies on B A

7. Draughtsman or Carom Coin Appearance

8. Under anaerobic condition : on bl agar shows β hemolysis due to O2 labile hemolysin O. In Liquid media : such as Glucose broth : uniform turbidity. Rapidly undergo autolysis due to activity of intracellular enzymes. Autolysis is enhanced by : bile salts, Sodium lauryl sulphate Heat killed cultures do not undergo autolysis

9. Biochemical reactions Ferment sugars : produce acid but no gas, fermentation of Inulin : useful test to differentiate them from streptococci Bile solubility test : few drops of 10% sodium deoxycholate added in 1 ml of overnight broth culture: culture clears due to lysis of cocci (presence of amidase that cleavs the bond betn alanine & muramic acid in peptidoglycan , it activates bile salts & causes autolysis) Catalase & Oxidase negative

10. Resistance Easily destroyed by heat Sensitive to most of the antibiotics Optochin sensitive: useful to differentiate pneumococci from streptococci

11. Antigenic structure Capsule : important Ag: capsular polysaccharides : it diffuses in cuture media or infective exudates & tissues, SPECIFIC SOLUBLE SUBSTANCE (SSS) Classification is based on capsular polysaccharides, more than 90 serotypes: mainly based on Agglutination, Precipitation of SSS with specific serum: detected by QUILLUG REACTION

12. * * * * * * Inhibits the action of complement Complement receptor Fc receptor S. Pneumoniae capsule Targets for protective antibody

13. QUILLUG REACTION Described by Neufeld (1902): suspension of S pneumoniae is mixed on a glass slide with a drop of specific antiserum & loopfull of methylene blue solution Homologous antiserum capsule become swollen Test can be directly done on sputum in Ac pneumonia cases, CSF: in meningitis cases

14. QUELLUNG REACTION

15. Other Antigens ‘C’ carbohydrate Ag : abnormal protein ( β globulin) that precipitate with somatic C Ag in ac cases. This is known as CRP (C reactive protein) test : passive agglutination by using latex particles coated with anti CRP antibodies Toxins : pneumolysin : cytotoxic & complement activating properties. Immunogenic.

16. PATHOGENECITY Colonised in nasopharynx : causes middle ear inf , paranasal sinusitis, direct spared to resp tract 80% lobar pneumonia & 60% brochopneumonia , may cause tracheobronchitis & empyma Lobar pneumonia: usually persons immunity is lowered Bronchopneumonia: especially after viral infection

17. Chronic bronchitis : copious respiratory secretions Meningitis : serious inf secondary to pneumococcal inf like pneumonia, otitis media, sinusitis etc Suppurative lesions in other parts of the body: arthritis, peritonitis, keratitis , dacrocystitis

18. Pathogenesis of pneumococci

19. EPIDEMIOLOGY Source of inf : human carriers, patients, transmitted by droplet nuclei, droplets Host resistance lowered by resp viral inf , pulmonary congestion, stress, malnutrition, immunodeficiency, alcoholism Splenectomy , sickle cell anaemia

20. Laboratory diagnosis Specimen: sputum, CSF, blood, urine Microscopy: rusty sputum in ac cases, gram stain: gram + ve diplococci Culture: on blood agar: incubated at 37 0 C under 5-10% CO2. blood culture in Ac condition Animal inoculation: mouse is used

21. Antigen detection: demonstration of SSS in CSF . Co-agglutination test: suspension of killed Staph aureus are coated with specific pneumococcal antibodies bound to protein A of Staph aureus cell wall When live or dead strept pnemoniae in CSF is mixed with suspension of Staph aureus visible co-agglutination is seen

22. TREATMENT Penicillin is still first choice of drug , in milder cases amoxicillin is used Erythromycin, tetracycline Third generation cephalosporins Vancomycin : reserve drug

23. vaccines

24. Difference between Strepto pneumoniae Viridance streptococci Morphology Capsulated, lanceolate shape,diplococci Non-capsulated, oval/rounded cells in chains Quellung reaction Positive Negative Colonies on B A Initially dome shaped, later ‘draughtsman’ colonies Dome shaped Growth in liq media Uniform turbidity Granular turbidity Bile solubility Positive Negative Optochin sensitivity Positive Negative Inulin fermentation Positive Negative

25. Other streptococci a) group B streptococci Streptococcus agalactiae : A member of the normal flora of the female genital tract and rectum. Up to about pregnant women carry it. Important in Neonatal infection : a) Early Onset Diasease : d eve within 24-48 hrs after birth Inf aquired in utero or during passage thr ’ birth canal Associated with: Premature birth PROM High mortality rate Disease present as Respiratory distress syndrome or septicemia or meningitis a)Early-onset Disease: severe disease develops within 24 – 48 hrs. after birth. Infection acquired either in-utero or during passage through birth canal.

26. Late-onset Disease: Often occurs in full term neonates without any underlying disease. Infection occurs in the 2 nd week of birth. Prognosis better than early onset: Mortality rate about 10%. Usually present as meningitis. Treatment: Penicillin /Ampicillin Sometimes may be combined with Gentamicin.

27. Gr B Streptococci identified by CAMP (Christie, Atkins, Munch-Peterson) Test: accentuated zone of hemolysis when inoculated perpendicular to streak of Staphylococcus aureus Human pathogens ar capsulated

28. CAMP test

29. Group c streptococci Streptococcus equisimilis : Predominantly animal pathogen Human inf : URTI, endocarditis, osteomyelitis, brain absses pneumonia, purperial sepsis Resistance to penicillin, Gentimicin is drug of choice Produce : streptolysin O, streptokinase, other extracellular substances

30. Group f streptococci Poorly grown on blood agar Known as minute streptococci Streptococcus MG : isolated from primary atypical pneumonia, α hemolytic Demonstration of agglitinins to strep MG diagnostic test for mycoplasma ( heterophilic Ag)

31. Group D Streptococci Has 2 main subgroups : i) Entrococcal ii) Non- Enterococcal Both are part of the normal intestinal flora. 1) Enterococci : can grow in the presence of 40% bile & 6.5% sodium chloride. They are generally resistant to Penicillin, but sensitive to Ampicillin.

32. 2 Main Human Pathogens: Enterococcus faecalis Enterococcus faecium

33. Non-enterococci: cannot grow in presence of 6.5% NaCl main human pathogen Strep.bovis they cause UTI, endocartditis and wound inf

34. - Haemolytic Streptococci Formarly called Streptococcus viridance Commensals of URT & mouth Produce α hemolysis on blood agar Spp : Strep. m itis , Strep mutance : dental carries , Strep salivaris , Strep sanguis Usually non pathogenic, occasionally cause inf in pre-existing cardiac lesions (bacterial endocarditis) Strep sanguis : after tooth extraction or dental procedures, prosthetic valves or congenital heart ds: predisposing factors

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