Oral microbiology

MICROBIOLOGY

AYDIN ÇÖL
ORAL MICROBIOLOGY

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The oral cavity is the most complex and the most accessible microbial ecosystem of the human body.

• The teeth,

• gingivae (gums),
• tongue,
• throat and
• buccal mucosa (cheeks)

all provide different surfaces for microbial colonization.

Introduction to oral microbiology


The constant production of saliva and intermittent provision of sugars and amino acids from ingested food provides nutrients for microbial growth.
The human oral cavity is home to about 700 identified species of bacteria.

This number will probably turn out to be closer to 1000 in the future, when all taxa and phyla have been recorded.

It is also home to at least 30 species of fungi (mainly of the genus Candida), several species of protozoa (which graze on the bacteria for food), and various intracellular viruses.

At diseased sites there is a tendency for higher numbers of different species to be present, perhaps 200 or more.
Generalizing, in a single subject it is usual to find between 20 – 50 species of bacteria at healthy oral sites.
The organisms present in the oral cavity are a mixture of commensals
and pathogens.

A commensal microorganism is defined as one that lives on or within a host but does not cause any apparent disease.

Many of the cultivated bacteria present in the mouth probably

contribute to oral diseases to a greater or lesser extent, because these
diseases are almost always associated with polymicrobial infections
There are very few organisms in the oral cavity and nasopharynx that can be considered overt pathogens.

• Streptococcus pyogenes (Group A Streptococcus),

• Streptococcus pneumoniae(Pneumococcus),
• Neisseria meningitidis(Meningococccus) and
• Haemophilus influenzae


all reside within the nasopharynx and have the potential to cause life-threatening diseases.

Mutans streptococci and

other acidogenic bacteria

fermentable carbohydrate

organic acids

dissolution of tooth structure

(enamel, cementum, dentin)

CARIES

Etiology of the major bacterial diseases in the oral cavity

Reversed by plaque removal

accumulation of dental plaque gingival inflammation


exacerbated by systemic factors
e.g. pregnancy , puberty

GINGIVITIS

Colonization of subgingival regions
by specific groups of organisms

expression of virulence factors

e.g. proteases, leukotoxin

Destructive immune responses

Loss of periodontal tissue including
gingiva, periodontal ligament
and alveolar bone

PERIODONTITIS

Important oral diseases, their manifestations and the major microorganisms involved.
Microorganisms implicated

Streptococcus, Lactobacillus, Actinomyces (root caries)

Disease

Caries

Description

Decay (loss) of tooth enamel (dental caries) or dentin (dentinal caries), or root dentin (root aries)

Description

Redness and swelling (inflammation) of the
gingival tissues (gums)

Microorganisms implicated

Actinomyces, Fusobacterium, Bacteroides, Prevotella
Disease

Gingivitis

Important oral diseases, continued

Disease

Pulpitis
Description

Infection of the pulp, inflammation around the apex of the root, leading to abscess formation (periapical granuloma)
Microorganisms implicated

Fusobacterium, Dialister, Peptostreptococcus, Porphyromonas

Important oral diseases, continued

Disease

Periodontitis
Description

Inflammation and either rapid (aggressive,

either generalized or localized) or slower
(chronic) destruction of the tissues supporting the tooth
Microorganisms implicated

Aggregatibacter (localized), Porphyromonas, Treponema, Tannerella, Fusobacterium,

Prevotella
Important oral diseases, continued

Microorganisms implicated

Infection and destruction of tissues surrounding a dental titanium implant
Description

Staphylococcus, Pseudomonas,

Porphyromonas, Prevotella
Disease

Implantitis

Important oral diseases, continued

Disease

Halitosis

Description

Oral malodor


Microorganisms implicated

Fusobacterium, Porphyromonas, Prevotella, Treponema, Eubacterium

Important oral diseases, continued

Description

Redness and inflammation of the pharynx
Microorganisms implicated

Group A Streptococcus, Neisseria,

Haemophilus, Coxsackie A virus
Disease

Pharyngitis

Important oral diseases, continued

Description

Infection and inflammation of the tonsils
Microorganisms implicated

Group A Streptococcus, Haemophilus

Disease

Tonsillitis

Important oral diseases, continued

Description

White patches on the buccal mucosal epithelium or tongue
Microorganisms implicated


Candida, human papilloma virus (HPV)
Disease

Leukoplakia

Important oral diseases, continued

Description

Reddening and inflammation of the oral mucosa
Microorganisms implicated

Candida albicans, Candida tropicalis, other Candida species

Disease

Stomatitis

Important oral diseases, continued

Description

Hard swelling (cyst) within the gums
Microorganisms implicated

Actinomyces israelii

Disease

Actinomycosis

Important oral diseases, continued

Important oral diseases, continued

Disease


Cold sores

Description

Surface (superficial) red, dry lesions close to the lips
Microorganisms implicated

Herpes simplex virus (HSV)

QuestIons?

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