Download Oral streptococci

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
• GPC, chains or pairs,
catalase negative
• Alpha, beta or nonhaemolytic
• Mouth, pharynx, gut,
vagina
A-G
Bacteriology
of the
streptococci
Beta
haemolysis
Alpha
Pneumococci often
grow as
“draughtsman”
colonies
Oral streptococci (1)
• 50% of population of tongue and saliva
• 25% of population of supragingival & gingival
plaque
• Most are alpha haemolytic (“viridans
streptococci”)
Oral streptococci (2)
Samaranayake 3rd ed. Chapter 11
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
Mutans streptococci
• Group name for 7 different species
• S. mutans: important role in caries
– Associated with initiation & progression
– Animal studies
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
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
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
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
Beta-haemolytic streps
• Lancefield types A,B,C,D,F,G
• Type A usually = Streptococcus pyogenes
• Type B = S. agalactiae
Rebecca Lancefield
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
Pharyngitis: about a third of
cases are caused by
beta-haemolytic streptococci
Scarlet fever
“Circumoral pallor”
Streptococcal pyrogenic
exotoxins; Spe A associated with
scarlet fever
(previously “erythrogenic toxin”)
Impetigo:
Streptococcus
pyogenes
and/or
Staphylococcus
aureus
Distinct
border
Erysipelas:
limb
Cellulitis:
often streptococcal
Cellulitis caused by Staphylococcus aureus
Skin and soft tissue infections:
different planes involved
Uvulitis
Causes include Haemophilus influenzae type b,
S. pyogenes
May progress to respiratory obstruction
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
S. pyogenes
• Non-suppurative complications: acute
rheumatic fever (ARF), acute
glomerulonephritis (AGN)
• ARF: heart tissues, joints and other tissues
• AGN: kidneys
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
Group C and group G streps
• Pharyngitis
• Skin and soft tissue infections
• Toxic and post-streptococcal complications
rare
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
“S. bovis”
• “S. bovis” has now been split into several
new, named species/subspecies.
• These include S. gallolyticus,
S. infantarius & S. pasteurianus
Alpha haemolytic streptococci
• S. pneumoniae – the pneumococcus;
capsulated
• “Viridans streptococci”
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
S. pneumoniae (pneumococcus)
•
•
•
•
•
Pneumonia
Meningitis
Bacteraemia/septicaemia
Upper respiratory tract infections
Etc etc
Pneumococcal infections: some risk factors
Pneumococcal vaccines
• Polyvalent polysaccharide
• Conjugate vaccine is newer and better
(routine childhood vaccine in USA)
Vegetation
Oral streptococci
are a common
cause of native valve
endocarditis
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
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)
… 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)
Joint prostheses
• Infection usually leads to pain, loss of
function … removal/?replacement
• Need for dental prophylaxis
contentious
Treatment
• Resistance problems especially in
– Pneumococci
– Enterococci
• Need bactericidal regimen if bacterial
endocarditis
• E.g. benzylpenicillin + gentamicin