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Understanding Oral Pathogens and Their Role in Periodontal Disease

This article explores the complexities of oral pathogens, particularly those linked to periodontal disease. It discusses how these pathogens can be ambiguous in nature, with mixed infections and various species contributing to the disease landscape. Notable bacteria such as Bacteroides, Porphyromonas, and Treponema denticola are highlighted for their role in human infections. The interplay between pathogenicity and the oral environment is examined, as well as the challenges in isolating specific pathogens due to varying conditions and sampling methods.

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Understanding Oral Pathogens and Their Role in Periodontal Disease

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  1. Introduction to Oral Pathogens

  2. There are some bacteria that cause a disease, but there are some diseases that bring about a condition that is ideal for the growth of some bacteria. -Pasteur

  3. Reasons for Uncertainty/Confusion in Defining 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.

  4. Bacteroides Group • B. fragilis • Porphyromonas • Prevotella

  5. Porphyromonas & Prevotella • Both gram-negative rods, black colonies on blood agar • After Bf, most common cause of human infection by anaerobic gram-negative bacilli • Habitat: oral cavity, upper alimentary, respiratory tracts, colon • unusual endotoxin • Infections: dental, sinus, pulmonary, human bite • Susceptible to penicillins

  6. General Characteristics of Bacteroides 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 strong trypsinlike activity • Periodontopathogen; associated with progressive attachment loss in subjects before therapy (RPP) and in refractory periodontitis

  7. Peptostreptococcus and Microaerophilic Streptococci • Confusing taxonomy • Some peptostrep reassigned to genus Streptococcus • Gram-positive cocci; chains; slow growers in O2 or CO2 • Habitat: normal oral flora; colon; female genital tract • Penicillin sensitive; aminoglycoside resistant

  8. Peptostreptococcus • Opportunists, often associated with other organisms • Present in cerebral abscess, pelvic peritonitis, anaerobic cellulitis, septic thrombophlebitis • Gas production; can be smelly

  9. Treponema denticola • Treponema; Greek, turning thread • General Characteristics: • Gram-negative, anaerobic, chemoorganotroph, very motile in highly viscous environment, rifampin resistant • Growth conditions: peptone-yeast extract-serum medium + fatty acids, cocarboxylase

  10. Background • Mounting evidence implicating T. denticola in the etiology 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. denticola antigen(s) are recognized by the humoral immune system or the characteristics of the antibodies produced.

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