Anaerobic cocci: proteolytics and enamel protectors
The group of anaerobic cocci in the oral microbiocenosis is represented predominantly by Peptostreptococcus and Veillonella. These microorganisms differ cardinally from each other in their type of metabolism and clinical significance.
Peptostreptococci include species such as Peptostreptococcus asaccharolyticus and P. stomatis. Their favorite habitat is the gingival sulci. They are characterized by a pronounced proteolytic type of metabolism. This means that peptostreptococci actively break down peptones and various amino acids, deriving energy from them, while their effect on carbohydrates is extremely weak.
Veillonella (Veillonella) possess a completely different function. Being gram-negative anaerobes and permanent residents of the oral cavity, they actively participate in the formation of dental plaque. However, their key feature is a potent anti-cariogenic effect.
The mechanism of this protection is based on the unique biochemistry of Veillonella:
- They do not ferment sugars directly, but utilize acidic products of carbohydrate metabolism from other bacteria (lactic acid, pyruvate, acetate).
- Veillonella utilize these aggressive acids down to completely safe water and carbon dioxide.
- As a result of this process, a rapid decrease in environmental acidity occurs, which prevents the demineralization of tooth enamel.
Lactobacilli: bacteria with a dual role
Rod-shaped bacteria are represented in the oral cavity by various species of lactobacilli, among which Lactobacillus acidophilus, L. brevis, and L. fermentum are the most significant. In dental microbiology, it is customary to speak of the paradoxical dual role of these microorganisms.
- Protective function. Lactobacilli are a crucial link in colonization resistance. They physically block receptors on the surface of mucosal epithelial cells, preventing foreign agents from attaching, and exhibit pronounced microbial antagonism toward the pathogenic flora.
- Pathogenic function. Possessing the ability for extremely active carbohydrate fermentation, lactobacilli produce a colossal amount of lactic acid. It is precisely this local acidification of the environment that is the triggering factor in the development of dental caries.
Strict anaerobes and periodontal pathology
Among the microflora responsible for the development of periodontal pathology, strict anaerobes occupy a leading place. This group includes Bacteroides (Bacteroides fragilis), Prevotella (Prevotella melaninogenica), and Porphyromonas (Porphyromonas gingivalis).
The energy metabolism of these bacteria is based on the breakdown of glucose, resulting in the formation of a complex mixture of various organic acids. From a clinical perspective, it is important to understand that these bacteria (especially P. melaninogenica) are permanently present in the gingival pockets of adult patients. This entire group of microorganisms is recognized as the main causative agents of destructive periodontal diseases.
Fusobacteria, spirochetes, and actinomycetes
The autochthonous (resident) microflora includes fusobacteria, such as Fusobacterium periodontium and F. nucleatum. Biochemically, they differ in that they synthesize butyric and lactic acids from glucose and peptones. Their most important feature is the tendency to form stable microbial associations, most often with spirochetes.
Spirochetes (specifically treponemes Treponema denticola and T. vincentii) are localized deep within the gingival pockets. Their main clinical danger lies in pathogenic synergism. Combining their aggression factors with fusobacteria and bacteroides, treponemes cause a severe dental disease — acute necrotizing ulcerative gingivostomatitis (Vincent's infection).
In addition, actinomycetes (species Actinomyces viscosus, A. naeslundii) as well as actinobacilli (Aggregatibacter spp.) are permanently present in this biotope. The latter colonize the oral mucosa, taking direct part in the formation of soft dental plaque and dense dental calculus. Working in association with other microbes, actinobacilli significantly accelerate the development of both caries and periodontal inflammation.
Briefly: answers to topical questions
Which species of spirochetes (treponemes) are part of the normal and pathological oral flora?
The following treponemes have been confirmed as sources in the oral cavity biotope:
- Saprophytic treponemes (Treponema spp.) are non-pathogenic species residing in the oral cavity.
- Dominant species of gingival pockets: T. denticola and T. vincentii — in association with fusobacteria and bacteroides, they cause acute necrotizing ulcerative gingivostomatitis.
Spirochete, Fusobacterium, and Bacteroides — the "Super Fatal Bouquet" of Vincent (helps memorize the association of bacteria causing Vincent's acute necrotizing ulcerative gingivostomatitis).
Class and exam questions
What is the anti-cariogenic effect of Veillonella?
Veillonella utilize acidic metabolic products of other bacteria (lactate, pyruvate, acetate), breaking them down into water and carbon dioxide. This reduces the overall acidity of the environment and prevents dental enamel demineralization.
Why are lactobacilli considered microbes with a dual function?
On the one hand, lactobacilli protect the mucosa by blocking epithelial cell receptors and suppressing pathogens. On the other hand, they actively ferment carbohydrates with the release of lactic acid, which provokes the development of caries.
What association of microorganisms causes Vincent's gingivostomatitis?
Vincent's acute necrotizing ulcerative gingivostomatitis results from the pathogenic synergism of three groups of anaerobes: spirochetes (treponemes), fusobacteria, and bacteroides.
What role do actinobacilli (Aggregatibacter) play in the oral cavity?
They are permanent inhabitants of the mucous membrane and actively participate in the formation of dental plaque and calculus, contributing to the development of periodontitis in association with other flora.
What else to study on this topic
- Mechanisms of adhesion of anaerobic bacteria to epithelial cells and tooth enamel
- Biochemical pathways of organic acid utilization by Veillonella
- Pathogenesis of Vincent's acute necrotizing ulcerative gingivostomatitis
- The process of biofilm formation and dental calculus mineralization
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