Aggregatibacter actinomycetemcomitans

Also called: A. actinomycetemcomitans, Aa

📍 Gum pockets, particularly in aggressive periodontitis

Campylobacter rectus

C. rectus (Cr)

📍 Subgingival plaque, deep periodontal pockets

Campylobacter rectus is an opportunistic periodontal pathogen whose endotoxin-like toxin has been repeatedly associated with adverse pregnancy outcomes, including low birth weight and intrauterine growth restriction (IUGR). It is a key organism to screen in the preconception and prenatal window.

Candida albicans

Also called: Candida

📍 Oral mucosa, tongue, dentures, throat

Enterococcus faecalis

E. faecalis

📍 Root canal systems, deep dentin layers of teeth, areas of previously treated teeth, occasionally in periodontal pockets

Epstein–Barr Virus

EBV

📍 Salivary glands, throat, oral epithelial cells, immune cells (B lymphocytes)

Fusobacterium nucleatum

Also called: F. nucleatum, Fn

📍 Gum pockets, tongue, oral biofilm

Fusobacterium nucleatum is a Gram-negative anaerobe and the 'bridge' pathogen of the oral microbiome — it physically links early and late colonizers in the biofilm and facilitates translocation of other organisms (including red-complex partners Porphyromonas gingivalis and Tannerella forsythia) across epithelial and placental barriers. It has been cultured from placental tissue in preterm-birth cases and is enriched in colorectal tumor tissue. The dedicated deep-dive is the F. nucleatum guide.

Helicobacter pylori

H. pylori

📍 Stomach lining, can be detected in dental plaque, may persist in the oral cavity as a reservoir

Klebsiella pneumoniae

K. pneumoniae

📍 Throat, back of the tongue, dental plaque, can colonize oral secretions

Porphyromonas gingivalis

Also called: P. gingivalis, Pg

📍 Deep gum pockets, subgingival biofilm

Porphyromonas gingivalis is a Gram-negative anaerobe and the 'keystone pathogen' of periodontitis. It is the central member of the red complex, operating alongside Tannerella forsythia and Fusobacterium nucleatum; its gingipain proteases degrade host defenses and drive the chronic low-grade CRP / IL-6 inflammatory signature most relevant to cardiovascular, metabolic, and pregnancy risk. The dedicated deep-dive is the P. gingivalis guide; the Oral Pathogens & Preconception Fertility brief links it to the preconception pathway.

Prevotella intermedia

P. intermedia (Pi)

📍 Subgingival plaque, periodontal pockets

Prevotella intermedia is a periodontal pathogen notable for its strong hormonal responsiveness. Elevated progesterone increases its virulence and abundance, making it a particular concern during pregnancy, where it contributes to pregnancy gingivitis and adverse reproductive outcomes.

Staphylococcus aureus

S. aureus (including MRSA strains)

📍 Nasal passages, throat, tongue surface, dental plaque, can colonize oral wounds or sores

Streptococcus mutans

Also called: S. mutans

📍 Tooth surfaces, dental plaque

Streptococcus mutans

S. mutans (Sm)

📍 Tooth surfaces, dental plaque, oral biofilm

Streptococcus mutans is best known as the primary bacterial cause of tooth decay. However, groundbreaking 2025 research published in Nature Communications identified a variant of S. mutans that produces a metabolite capable of damaging dopamine-producing neurons — establishing the first direct microbial pathway linking an oral bacterium to Parkinson's disease. The study analyzed stool samples from nearly 500 Parkinson's patients and 234 healthy controls.

Tannerella forsythia

Also called: T. forsythia, Tf

📍 Deep gum pockets

Tannerella forsythia is a Gram-negative anaerobe and one of the three members of the 'red complex' — the polymicrobial trio (alongside Porphyromonas gingivalis and Fusobacterium nucleatum) most strongly associated with severe, tissue-destructive periodontitis and the systemic inflammatory burden that travels with it. It produces a unique surface glycosidase (NanH) and virulence factors that help the subgingival biofilm degrade periodontal tissue and evade host defenses.

Treponema denticola

Also called: T. denticola, Td

📍 Deep gum pockets, inflamed periodontal tissue