Oral Microbiome in Disease

This set of vocabulary flashcards covers the microbiology of dental caries and periodontitis, including historical hypotheses, key pathogens, virulence factors, and modern molecular identification techniques.

Periodontitis

A chronic infection of the tooth supporting structures (the periodontium) characterized by progressive bone loss and soft tissue damage. Caused by immune response

Open-ended molecular techniques

16S rRNA sequencing, metagenome sequencing, metatranscriptome sequencing. “Omics technologies”

Non-specific plaque hypothesis

Collective community of mixed bacteria in saliva, added carbohydrates = tooth demineralization.

Specific plaque hypothesis

Specific bacterial species in dental biofilm are capable of causing caries.

Key players in dental caries

S. mutans, lactobacilli, actinomyces, non-mutans streptococci

Streptococcus mutans

The most important etiological agent of dental caries, primarily responsible for the initiation of coronal carious lesions. 8 serotypes in humans. Acidogenic, acidouric, adheres to tooth surfaces

S. mutans virulence factors

Acidogenic (PTS system), Acidouric (proton pump), sucrose independent adherence (SpaP; Ag I/II, AgB; attachment to dental pellicle), sucrose independent adherence (glucose - glucosyltransferases - glucan binding proteins, dextranase). Fructose stored as energy.

Lactobacilli

Involved in the progression of caries into dentin rather than caries initiation. Highly acidogenic (produces lactic acid)

Is actinomyces linked to root caries

evidence does NOT support

non-mutans streptococci

s. mitis, s. intermedius, s. sanguinis

Ecological plaque hypothesis

The theory that dental plaque is a biofilm where the significance of pH determines the shift between health and caries.

Candida albicans

An emerging fungal cariogen that synergizes with $Streptococcus mutans$ and is associated with early childhood caries (ECC). Coinfection = more severe caries

Do not produce acids

prevotella, selenomonas

Scardovia wiggsiae

An emerging acidogenic and aciduric cariogen frequently associated with early childhood caries (ECC), often co-existing with $S. mutans$. Failed to induce caries in experimental animals.

Deiminase

An enzyme system that converts arginine to citrulline, producing an ammonium byproduct that neutralizes acids to promote oral health.

Criteria for defining periodontal pathogens

Association, Elimination, Host response, possession of virulence factors, induce destruction, risk assessment (longitudinal studies)

Aggressive localized periodontitis

A. actinomycetemcomitans

Red complex

A group of three bacteria ($P. gingivalis$, $T. forsythia$, and $T. denticola$) that are strongly associated with chronic periodontitis.

Keystone pathogen hypothesis

The theory that certain species, such as p. gingivalis, trigger microbial dysbiosis by subverting the immune response even at low abundance.

16S rRNA sequencing

An open-ended molecular technique used for the targeted sequencing of the bacteriome to identify microbial composition.