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. Beta haemolysis

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

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)
Meningitis
Bacteraemia/septicaemia
Upper respiratory tract infections
Etc etc

35. Pneumococcal infections: some risk factors

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

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

39. 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

40. But don’t forget …
Recommendation 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)

41. … 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)

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

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