The Oral Microflora

The Oral Microflora
M.R.Milward
School of Dentistry
Contents
1.
Definitions
2.
Microbial habitats
3.
Factors affecting growth
4.
Identification
5.
Important oral bacteria
6.
Clinical examples
7.
Flora in dental plaque
8.
Changes in the oral flora with age
9.
Bacterial endocarditis
DEFINITIONS:
•
•
•
•
•
•
•
•
•
•
•
•
•
Aetiology: The cause of phenomena (eg. disease)
Pathology: Structural & functional changes caused by disease
Pathogen(ic): Producing disease
Pathogenesis: The mode of development of a disease
Pathological: Relating to pathology or disease
Commensal: An organism living in/on an organism of another species without injuring
the host
Parasite: An organism living in/on and at the expense of another organism (the host).
Equivalent to a pathogen
Opportunist Pathogen: A commensal organism that can cause disease in certain
circumstances
Symbiosis: The mutally beneficial association between two organisms
Aerobic Organism: requiring oxygen for growth and replication
Anaerobe: Organism that grows and replicates in the absence of oxygen; not necessarily
killed by oxygen
Strict anaerobe: Anaerobe killed by oxygen
Facultative anaerobe: Organism capable of growth and replication in the presence or
absence of oxygen
Oral Microbiology:
PD Marsh & MV Martin
Microbial habitats
Habitat
Comment
Lips, cheek, palate
•Biomass limited by desquamation
•Some surfaces have specialised host
cell types
Tongue
•Highly papillated surface
•Acts as a reservoir for obligate
anaerobes
Teeth
Non-shedding surface enabling large
masses of microbes to accumulate
(dental plaque biofilm)
Teeth have distinct surfaces for
microbial colonisation (e.g. Smooth
surfaces, pits & fissures etc) will
support distinct micro flora due to
their biological properties
Gingival crevice /
pocket
Health (aerobic), disease (anaerobic)
Oral Microbiology:
PD Marsh & MV Martin
Oral Microbiology:
PD Marsh & MV Martin
Factors Affecting Growth of
Microorganisms in the oral cavity
1. Temperature
2. REDOX Potential / Anaerobiosis
3. pH
4. Nutrients (endogenous & exogenous (diet))
5. Host Defences (Innate & Acquired immunity)
6. Host genetics (changes in immune response etc)
7. Antimicrobial agents & inhibitors
Oral Microbiology:
PD Marsh & MV Martin
Identification / classification
Characteristic
Examples
Cellular morphology
Shape, Gram staining, size,
associations
Colonial appearance
Pigmentation, haemolysis,
shape, size
Carbohydrate fermentation
Acid or gas production
Amino acid hydrolysis
Ammonia production
Pattern of fermentation
products
e.g. Lactate, acetate
Preformed enzymes
e.g. glycosidases
Antigen
Monoclonal/polyclonal
antibodies to surface proteins
DNA
Base composition
Pearson education
jlindquist.net
Bmb.leeds.ac.uk
GRAM POSITIVE = BLUE
e.g. Streptococci, Staphylococci
GRAM NEGATIVE = RED/PURPLE
e.g. E. coli, Fusobacterium, Porphyromonas
Complexity of Micro flora
Oral Microbiology:
PD Marsh & MV Martin
Important Oral Bacteria
1. Gram Positive organisms:
•
•
•
•
•
Bulk of oral bacteria
Rods (bacilli), cocci or irregular shape (pleomorphic)
Oxygen tolerance varies from aerobes to strict anaerobes
Most are fermentative
Cell wall has thick peptidoglycan layer (penicillin has effect by interfering
production of this layer)
Three important genera:
• Actinomyces, facultative anaerobe
• Lactobacillus, produce lactic acid, facultative anaerobe, role in dentine caries
rather than enamel caries
• Streptococcus facultative anaerobic cocci, produce lactic acid some
implicated in caries
Streptococci:
• Isolated from all sights of the mouth
• Large proportion of resident microflora
• Majority α-haemolytic
Strep mutans:
• Associated with caries
• Associated with bacterial endocarditis
Strep salivarius:
• Colonise mucosal surfaces especially the tongue
Strep angiosus:
• Isolated dental plaque & mucosal surfaces
• Seen in maxillofacial infections, brain, liver etc
Strep mitis:
• Opportunistic pathogens e.g. endocarditis
Important of Streptococci in the oral
and their properties
Production of
Important
Oral Species
Growth on
hard
surfaces
S mutans
Cariogenic
Endocarditis
isolates
+
+++
+
+
+
++
++
+
+
+
+
+++
S milleri
+
-
+
+
+
S salivarius
-
-
+
-
-
Insol.
Extracellular
polysaccharide
Acid
+
+
S sanguis
+
S mitior
Distribution of Streptococci in the oral
cavity
Species
S.mutans
S. mitior
S. salivarius
Cheek
+++
-
Tongue
+++
++
Saliva
+/+++
++
Tooth
++
+++
-
Actinomyces:
• Short pleomorphic rods with branching
• Major proportion of plaque
• Increase in gingivitis
• Associated with root caries
Important Oral Bacteria
2. Gram Negative organisms
Many Gram-negative bacteria found in the mouth, especially in
established/subgingival plaque
Cocci, rods, filamantous rods, spindle shaped or spiral shaped
Range of oxygen tolerance but most important strict or facultative
anaerobes
Some fermentative, produce acids which other organisms use acids as an
energy source, others produce enzymes which break down tissue
Cell wall different to Gram positive with a thin peptidoglycan layer, has
B-lactamase which breaks down penicillin, also has LPS/endotoxin
Most important Gram negative bacteria:
• Porphyromonas: P. gingivalis major periodontal pathogen
• Prevotella: P. intermedia a periodontal pathogen
• Fusobacterium: F. nucleatum periodontal pathogen
• Actinobacillus/Aggregatibacter: A.actinomycetemcomitans associated with
aggressive periodontitis
•Treponema: group important in acute periodontal conditions i.e ANUG
• Neisseria
• Veillonella
Clinical examples
Flora of normal, healthy dentate
mouth
% (approx)
Bacteria
Streptococci
85%
Veillonella
Gram positive Diptheroids
Gram negative anaerobic rods
5-7%
Neissaeria
2%
Lactobacilli
1%
Staphylococci & Micrococci
2%
Filamentous bacteria
Remainder
Other bacteria, fungi,
protozoa & viruses
Difference between mature supra &
sub-gingival plaque
Characteristic
Grams stain
Supra gingival
Gram + or -ve
Cocci, branching
Morphotypes
rods, filaments &
spirochaetes
Facultative, some
Energy Metabolism
anaerobic
Mainly ferment
Energy source
carbohydrate
Motility
Few
Pathology
Caries & gingivitis
Sub gingival
Mainly Gram –ve
Mainly rods &
spirochaetes
Mainly anaerobic
Many proteolytic
forms
Many
Gingivitis &
periodontitis
Distribution of bacteria in smooth
surface dental plaque over 3 week
period
Bacteria
Gram +ve cocci
Gram +ve rods
Gram –ve cocci
Gram –ve rods
6 hrs
79
8
5
8
Distribution (%)
1 day 2 days 7 days 3 wks
81
71
60
31
7
10
20
56
5
11
12
9
7
8
8
4
Oral flora changes with age
Time during a lifetime
Newborn
6 months
Tooth eruption
Child to adult
Loss of teeth
Dentures etc
MAJOR COMPONENTS & CHANGES IN ORAL FLORA
Oral cavity sterile. Soon colonised by facultative and
aerobic organisms; esp S. salivarius
Flora becomes more complex & includes anaerobic
orgs eg. Veillonella sp. & Fusobacteria
Increase in complexity. S sanguis, S mutans and A
viscosus appear. New habitats include hard surfaces
and gingival crevice.
Various anaerobes frequently found inc. Members
of the Bacteroidaceae. Spirochaetes isolated more
frequently
Disappearance of S mutan, S sanguis, spirochaetes
and many anaerobes
Reappearance of bacteria able to grow on hard
surfaces
Bacterial endocarditis
Infective endocarditis (IE) is a rare condition with significant morbidity
and mortality. It may arise following bacteraemia in a patient with a
predisposing cardiac lesion. In an attempt to prevent this disease, over
the past 50 years, at-risk patients have been given antibiotic prophylaxis
before dental and certain non-dental interventional procedures.
Bacterial endocarditis is an infection in the lining of the heart or heart
valves, that could damage or destroy these valves. According to the
American Heart Association, bacterial endocarditis happens when
bacteria in the bloodstream, called bacteraemia, lodge on heart tissue
that has been damaged or on abnormal heart valves.
Bacterial endocarditis
escardio.org
Causative organisms in infective
endocarditis:
Micro organism
Cases (%)
TOTAL STREPTOCOCCI
60
Strep. viridans
35
Strep. faecalis
13
Microaerophilic Streptococci
3
Anaerobic Streptococci
2
Others
7
TOTAL STAPHYLOCOCCI
25
Staph. aureus
20
Staph. epidermidis
5
MISCELLANEOUS
5
CULTURE NEGATIVE
10
Adults and children with structural cardiac conditions:
Regard people with the following cardiac conditions as being at risk of
developing infective endocarditis:
• acquired valvular heart disease with stenosis or regurgitation
• valve replacement
• structural congenital heart disease, including surgically corrected or palliated
structural conditions, but excluding isolated atrial septal defect, fully repaired
ventricular septal defect or fully repaired patent ductus arteriosus, and
closure devices that are judged to be endothelialised
• hypertrophic cardiomyopathy
• previous infective endocarditis.
Advice
Offer people at risk of infective endocarditis clear and consistent information
about prevention,
including:
• the benefits and risks of antibiotic prophylaxis, and an explanation of why
antibiotic prophylaxis is no longer routinely recommended
• the importance of maintaining good oral health
• symptoms that may indicate infective endocarditis and when to seek expert
advice
• the risks of undergoing invasive procedures, including non-medical
procedures such as body piercing or tattooing.
When to offer prophylaxis
Do not offer antibiotic prophylaxis against infective endocarditis:
– to people undergoing dental procedures
– to people undergoing non-dental procedures at the following sites1:
upper and lower gastrointestinal tract genitourinary tract; this includes
urological, gynaecological and obstetric procedures,and childbirth
upper and lower respiratory tract; this includes ear, nose and throat
proceduresand bronchoscopy.
Do not offer chlorhexidine mouthwash as prophylaxis against infective
endocarditis to people at
risk undergoing dental procedures.
Managing infection
Investigate and treat promptly any episodes of infection in people at risk of
infective
endocarditis to reduce the risk of endocarditis developing.
Offer an antibiotic that covers organisms that cause infective endocarditis if
a person at risk of
infective endocarditis is receiving antimicrobial therapy because they are
undergoing a
gastrointestinal or genitourinary procedure at a site where there is a suspected
infection.
Further
Reading