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Streptococci and enterococci

Streptococci and enterococci. Streps are nasty …. Pneumococcus kills a million patients a year (mostly under 5 years old) Streptococcus pyogenes used to cause hospital epidemics with 90% mortality Bacterial endocarditis pre-antibiotics had 100% mortality. Streptococci and enterococci.

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Streptococci and enterococci

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  1. Streptococci and enterococci

  2. Streps are nasty …. • Pneumococcus kills a million patients a year (mostly under 5 years old) • Streptococcus pyogenes used to cause hospital epidemics with 90% mortality • Bacterial endocarditis pre-antibiotics had 100% mortality

  3. Streptococci and enterococci • GPC, chains or pairs, catalase negative • Alpha, beta or non-haemolytic • Mouth, pharynx, gut, vagina

  4. Bacteriology of the streptococci A - G

  5. Betahaemolysis

  6. Alpha

  7. Pneumococci often grow as “draughtsman” colonies

  8. Oral streptococci (1) • 50% of population of tongue and saliva • 25% of population of supragingival & gingival plaque • Most are alpha haemolytic (“viridans streptococci”)

  9. Oral streptococci (2) Samaranayake 3rd ed. Chapter 11

  10. Oral streptococci (3) • Major part of oral flora • Access to bloodstream: bacteraemia • Roles in disease • Infective endocarditis • Caries (especially S. mutans) • Abscesses • Oral (dentoalveolar, periodontal) • Extra-oral: Anginosus group

  11. Mutans streptococci • Group name for 7 different species • S. mutans: important role in caries • Associated with initiation & progression • Animal studies

  12. Streptococcus mutans and caries: why? • Sugar transport mechanisms • Multiple • Acid production (acidogenic) • Rapid production, including lactic acid • Acid tolerant (aciduric) • Extracellular polysaccharides • Part of plaque matrix • Intracellular polysaccharides

  13. Active immunisation • Antigens from mutans streps successfully used as vaccines to prevent caries in animal models • Potential to induce autoimmune damage? • Purified antigens which do not cross react now used in research • ?? Further development – economic constraints etc

  14. Passive immunisation: experimental studies • Suppress mutans streps with chlorhexidine • Administer monoclonal antibodies to mutans antigen • Recolonisation by mutans streps inhibited • Use transgenic plants to make dimeric MAbs

  15. Replacement therapies • Use engineered strains of S. mutans • Hillman’s work • Developed a strain with LDH knocked out • This strain also produces an antibiotic which gets rid of other strains of S. mutans (mutacin 1140) • Aiming for clinical trial … • More info: see Marsh & Martin, pages 142-3

  16. Beta-haemolytic streps • Lancefield types A,B,C,D,F,G • Type A usually = Streptococcus pyogenes • Type B = S. agalactiae Rebecca Lancefield

  17. S. pyogenes • Virulence factors: M proteins; erythrogenic toxins; streptolysins; hyaluronidase • Pharyngitis and local complications • Scarlet fever • Skin and soft tissue infections • Streptococcal toxic shock syndrome • Bacteraemia and septicaemia

  18. Pharyngitis: about a third of cases are caused by beta-haemolytic streptococci

  19. Scarlet fever “Circumoral pallor” Streptococcal pyrogenic exotoxins; Spe A associated with scarlet fever (previously “erythrogenic toxin”)

  20. Impetigo:Streptococcus pyogenesand/orStaphylococcus aureus

  21. Distinct border Erysipelas: limb

  22. Cellulitis: often streptococcal

  23. Cellulitis caused by Staphylococcus aureus

  24. Skin and soft tissue infections: different planes involved

  25. Uvulitis Causes include Haemophilus influenzae type b, S. pyogenes May progress to respiratory obstruction

  26. Acute streptococcal gingivitis “This condition affects the gingivae which can result in severe illness. The gingivae become red, swollen and full of fluid (oedematous), the temperature is raised and the regional lymph nodes are also enlarged. Lancefield Group A streptococci (S. pyogenes) can be isolated from the affected gingivae. This disease is usually preceded by a sore throat and hence it is possible that there is a direct spread of S. pyogenes from throat to gingivae.” Oral Microbiology 5th ed. 2009

  27. S. pyogenes • Non-suppurative complications: acute rheumatic fever (ARF), acute glomerulonephritis (AGN) • ARF: heart tissues, joints and other tissues • AGN: kidneys

  28. How about a vaccine? Group B strep neonatal sepsis: septicaemia, pneumonia, meningitis Prophylactic penicillin can be given to the mothers before birth in selected cases

  29. Group C and group G streps • Pharyngitis • Skin and soft tissue infections • Toxic and post-streptococcal complications rare

  30. Group D cocci • Enterococcus species and certain streptococci • Enterococci: nosocomial infections; UTI • Increasing isolations of vancomycin-resistant enterococci (VRE) • “S. bovis”: isolation from blood (bacteraemia, endocarditis) strongly associated with early colon cancer

  31. “S. bovis” • “S. bovis” has now been split into several new, named species/subspecies. • These include S. gallolyticus, S. infantarius & S. pasteurianus

  32. Alpha haemolytic streptococci • S. pneumoniae – the pneumococcus; capsulated • “Viridans streptococci”

  33. Viridans streptococci … Collectively, commensal streptococci are often called ‘viridans streptococci’ which refers to their a-haemolytic property (viridis = green). Not quite logically, this term also includes the few streptococci, such as those of the salivarius and mutans groups, that induce neither a not b haemolysis. Moreover, in common usage, the term excludes Str. pneumoniae … Medical Microbiology 17th ed, 2007 Greenwood D et al

  34. S. pneumoniae (pneumococcus) • Pneumonia • Meningitis • Bacteraemia/septicaemia • Upper respiratory tract infections • Etc etc

  35. Pneumococcal infections: some risk factors

  36. Pneumococcal vaccines • Polyvalent polysaccharide • Conjugate vaccine is newer and better (routine childhood vaccine in USA)

  37. Vegetation Oral streptococci are a common cause of native valve endocarditis

  38. Prevention of Infective Endocarditis • Clinical teachers will discuss current thinking & FoD practice • Involve cardiologist caring for patient • Stay up to date: read your dental journals

  39. But don’t forget … Recommendation 1.1.5 Any episodes of infection in people at risk of IE should be investigated and treated promptly to reduce the risk of endocarditis developing NICE Clinical Guideline 64 (UK, 2008)

  40. … and … Healthcare professionals should offer people at risk of IE … information about prevention, including … • the importance of maintaining good oral health NICE Clinical Guideline 64 (UK, 2008)

  41. Joint prostheses • Infection usually leads to pain, loss of function … removal/?replacement • Need for dental prophylaxis contentious

  42. Treatment • Resistance problems especially in • Pneumococci • Enterococci • Need bactericidal regimen if bacterial endocarditis • E.g. benzylpenicillin + gentamicin

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