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Introduction to

Oral Pathogens

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There are some bacteria that cause adisease, but there are some diseases thatbring about a condition that is ideal for the

growth of some bacteria.

-Pasteur

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Reasons for Uncertainty/Confusion inDefining Microbial Periopathogens

Periodontal disease may be periodontal diseases Mixed infections Large number of species present

Many species are difficult to grow Time of sampling may be wrong Different sites in same patient may have different

bacteria Opportunistic species grow as result of disease rather

than as cause. Association studies

Carrier states Phenotypically normal, but infected with pathogen Strains of putative pathogens may vary in virulence. Some

may harbor phage or plasmids.

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BacteroidesGroup

B. fragilis

Porphyromonas

Prevotella

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Porphyromonas & Prevotella

Both gram-negative rods, black colonies on bloodagar

After Bf, most common cause of human infectionby anaerobic gram-negative bacilli

Habitat: oral cavity, upper alimentary, respiratorytracts, colon

unusual endotoxin Infections: dental, sinus, pulmonary, human bite

Susceptible to penicillins

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General Characteristics ofBacteroides forsythus

Renamed in 1986 for fusiform Bacteroides

Gram-negative, anaerobic, pleomorphic often fusiform

Cells are nonmotile and have no flagella

This species demonstrates a distinctive surface layer Requires exogenous N-acetyl-muramic acid for growth

One of a few oral species demonstrating strongtrypsinlike activity

Periodontopathogen; associated with progressiveattachment loss in subjects before therapy (RPP) and inrefractory periodontitis

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Peptostreptococcus

Opportunists, often associated with otherorganisms

Present in cerebral abscess, pelvicperitonitis, anaerobic cellulitis, septicthrombophlebitis

Gas production; can be smelly

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Treponema denticola

Treponema; Greek, turning thread

General Characteristics:

Gram-negative, anaerobic,chemoorganotroph, very motile in highlyviscous environment, rifampin resistant

Growth conditions: peptone-yeast extract-

serum medium + fatty acids, cocarboxylase

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Background

Mounting evidence implicating T. denticolain theetiology of human periodontitis.

T. denticola overgrowth is synonymous with the

presence of clinical inflammation. Armamentarium of proteolytic, cytolytic, and adherence

properties

Meager and confusing information about which T.denticolaantigen(s) are recognized by the humoralimmune system or the characteristics of theantibodies produced.

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