MICROBIOLOGY ORAL MICROBIOLOGY AYDIN ÇÖL

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Introduction to oral microbiology 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.

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.

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

Etiology of the major bacterial diseases in the oral cavity Mutans streptococci and other acidogenic bacteria fermentable carbohydrate organic acids dissolution of tooth structure (enamel, cementum, dentin) CARIES

Reversed by plaque removal GINGIVITIS Reversed by plaque removal accumulation of dental plaque gingival inflammation exacerbated by systemic factors e.g. pregnancy , puberty

Colonization of subgingival regions by specific groups of organisms PERIODONTITIS 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

Important oral diseases, their manifestations and the major microorganisms involved. Caries Description Decay (loss) of tooth enamel (dental caries) or dentin (dentinal caries), or root dentin (root aries) Microorganisms implicated Streptococcus, Lactobacillus, Actinomyces (root caries)

Important oral diseases, continued Gingivitis Description Redness and swelling (inflammation) of the gingival tissues (gums) Microorganisms implicated Actinomyces, Fusobacterium, Bacteroides, Prevotella

Important oral diseases, continued 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 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 Implantitis Description Staphylococcus, Pseudomonas, Porphyromonas, Prevotella Microorganisms implicated Infection and destruction of tissues surrounding a dental titanium implant

Important oral diseases, continued Halitosis Description Oral malodor Microorganisms implicated Fusobacterium, Porphyromonas, Prevotella, Treponema, Eubacterium

Important oral diseases, continued Pharyngitis Description Redness and inflammation of the pharynx Microorganisms implicated Group A Streptococcus, Neisseria, Haemophilus, Coxsackie A virus

Important oral diseases, continued Tonsillitis Description Infection and inflammation of the tonsils Microorganisms implicated Group A Streptococcus, Haemophilus

Important oral diseases, continued Leukoplakia Description White patches on the buccal mucosal epithelium or tongue Microorganisms implicated Candida, human papilloma virus (HPV)

Important oral diseases, continued Stomatitis Description Reddening and inflammation of the oral mucosa Microorganisms implicated Candida albicans, Candida tropicalis, other Candida species

Important oral diseases, continued Actinomycosis Description Hard swelling (cyst) within the gums Microorganisms implicated Actinomyces israelii

Important oral diseases, continued Cold sores Description Surface (superficial) red, dry lesions close to the lips Microorganisms implicated Herpes simplex virus (HSV)

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