Streptococcus

STREPTOCOCCUS SPECIES

1. STREPTOCOCCUS Dr.M.Malathi Postgraduate final year Department of Microbiology Chengalpattu Medical College

2. Introduction Gram positive cocci Arrangement : chains or pairs Part of normal flora Causes pathogenic infections also

3. Classification of Streptococci Brown`s classification Lancefield grouping Griffith typing

4. Brown`s classification

5. Hemolysis

6. Lancefield grouping

7. Group A betahemolytic Streptococci Streptococcus pyogenes Morphology: Spherical to oval cocci Arranged in chains, more in liquid medium Why chain formation? Longest chain is produced by Streptococcus salivarius ( Commensal ) Non motile Non sporing

8. Gram positive cocci in chains

9. Cultural characteristics Aerobe and facultative anaerobe Temperature – 37 deg C Needs enrichment with blood or serum Blood agar – small colonies with beta type of hemolysis around them Liquid media – granular turbidity

10. Biochemical reactions Ferments sugars – acid , no gas Catalase negative PYR test ( Pyrolidonyl beta naphthylamide ) positive Ribose – not fermented Not bile soluble

11. Antigenic structure Structural antigens – Cell wall antigens Toxins Enzymes

12. Structural antigens Capsule – not antigenic Cell wall – Group specific carbohydrate Extraction methods: Lancefield`s acid extraction method Fuller`s method Maxted`s method Rantz and Randall`s method

13. Protein antigens M protein : most virulent; heat and acid stable, but susceptible to tryptic digestion. 80 types identified. Griffith typing. T protein : acid labile, trypsin resistant. Not virulent. R protein: not virulent Fimbrial antigens: for attachment in epithelial cells

14. Antigenic cross - reactions Streptococcus pyogenes Human Capsular hyaluronic acid Human synovial fluid Cell wall proteins Myocardium Group A carbohydrates Cardiac valves Cytoplasmic membrane antigens Vascular intima Peptidoglycan Skin antigens

15. Toxins and enzymes Streptolysin – O, S Pyrogenic exotoxin Streptokinase Deoxyribonucleases ( Streptodornase ) NADase Hyaluronidase Serum opacity factor

16. Pathogenicity Suppurative diseases: Respiratory infections Skin and soft tissue infections Genital infections Non suppurative sequelae: Acute rheumatic fever Acute glomerulonephritis

17. Respiratory infections Primary site – throat Adherence – by pili Tonsillitis Pharyngitis Otitis media Streptococcal pneumonia Throat infection – sequelae – Acute rheumatic fever

18. Skin and soft tissue infections Cellulitis Septicemia Erysipelas – diffuse infection – superficial lymphatics – older patients Impetigo – skin lesions – children – leads to sequelae – Acute glomerulonephritis

19. Cellulitis

20. Necrotising faciitis : M types 1 and 3 forming pyrogenic exotoxin A High fatality Flesh eating bacteria Shock, DIC Treatment with penicillin – not effective Vancomycin – DOC in life threatening infections

21. Effect of flesh eating bacteria 

22. Genital infections Normal inhabitants of the female genitalia Puerperal sepsis

23. Acute rheumatic fever Site of infection – Throat Prior sensitization is essential Serotype – Any Marked immune response Unaffected complement level Genetic susceptibility – present Repeated attacks – common Penicillin prophylaxis is essential

24. Acute glomerulonephritis Site of infection – Throat or skin Prior sensitisation – not necessary Serotype – 49,53-55,59-61 and 1,12 Moderate immune response C omplement level - lowered Genetic susceptibility – Absent Repeated attacks – Absent Penicillin prophylaxis is not indicated

25. Case history 7 year old girl Fever with severe sore throat Bilateral enlarged tonsils and exudates What investigation? What culture plate you will use?

26. Throat swab Direct Gram stain – GPC in chains Culture – Transport medium (Pike`s medium) Culture – sheep blood agar Rapid diagnostic kits with specific antisera Bacitracin sensitivity ASO titre Anti DNAase B

27. Case history Nine year old girl Fever and sore throat On throat culture – Group A Streptococci O/E, pain and tender swelling, palpable effusion of the right knee, culture of aspirate is negative. CXR – mild congestive heart failure Murmur heard at cardiac apex Diagnosis ? What investigation?

28. Check ASO titre

29. Case history Seven year old boy Skin infection Five days later, coloured urine and pitting oedema Elevated BP, 4+ proteinuria , elevated serum creatinine Diagnosis? What investigation?

30. Prophylaxis Penicillin prophylaxis fro the prevention of rheumatic fever Not needed for AGN

31. Treatment All are sensitive to Penicillin G If patient is having anaphylaxis for penicillin G  Give erythromycin Some strains are resistant to erythromycin

32. Group B beta hemolytic Streptococci Streptococcus agalactiae Neonatal infection Most common cause of neonatal meningitis Source – from the maternal vagina during birth GBS – puerperal sepsis, pneumonia Diagnostic markers – Hippurate hydrolysis, CAMP test

33. CAMP test Christie, Atkins and Munch- P eterson When S.agalactiae is inoculated perpendicular to a streak of S.aureus grown on blood agar  an accentuated zone of hemolysis occurs

34. CAMP TEST

35. Group C beta hemolytic Streptococci Streptococci equisimilis Upper respiratory infections Endocarditis , osteomyelitis , brain abscess Penicillin tolerance Treat with penicillin and gentamicin Source of streptokinase used for thrombolytic therapy in patients

36. Group F beta hemolytic Streptococci Streptococcus MG Grow poorly on blood agar Minute streptococci Streptococcus MG – alphalytic strain – isolated from Primary atypical pneumonia

37. Enterococcus E.faecalis E.faecium E.durans

38. Special features Grow in the presence of 40% bile 6.5% sodium chloride pH 9.6 Growth at 45degC Tiny magenta coloured colonies in Mac Conkey agar Heat resistant – survives 60degC for 30 minutes Pairs of oval cocci , arranged at an angle to each other Non hemolytic

39. Identification – mannitol , sucrose, sorbitol fermentation , bile Esculin hydrolysis Present in intestine, genital tract and saliva Urinary tract infection and wound infection. Intrinsically resistant to cephalosporins Treatment: Penicillin + Aminoglycosides Vancomycin

40. Viridans group Streptococci normally resident in the mouth and upper respiratory tract Alpha lysis on blood agar Cannot be categorised under lancefield antigenic groups Types: S.mitis S.mutans S.salivarius S.sanguis

41. Causes dental caries Tooth extraction – seeding into blood stream - endocarditis – hence give prophylactic antibiotics

42. Summary Types of hemolysis ? What is the basis for lancefield grouping? What is the basis for Griffith typing? Name one example for alpha hemolysis ? Name one example for beta hemolysis ? Name one example for gamma hemolysis ? Significant titre for ASO? What are the post streptococcal sequelae?