Periodontitis, Fusobacterium nucleatum, and Colorectal Carcinoma. A Review.

: Our review study addresses chronic periodontitis and its potential complications in the distal segments of the intestine and rectum. Subgingival colonization by gram-negative anaerobic bacteria such as Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Eikenella corrodens, and Fusobacterium nucleatum may, through haematogenous dissemination into non-oral tissues and organs, cause severe systemic diseases. In connection with colorectal carcinoma, the third most frequently diagnosed malignant tumor, special attention has been focused on the anaerobic rod Fusobacterium nucleatum, one of the key periodontal pathogens involved in periodontal pocket infections. A growing amount of direct and indirect evidence supports its role in the development, progression, and persistence of colorectal carcinoma in the distal colon and rectum. F. nucleatum possesses numerous virulence factors that underlie its remarkable infectious potential, not only within the oral cavity but also in the colonic environment, where they facilitate its integration into the dysbiotic microbiome and directly contribute to carcinogenesis in this region. Disruption of the physiological microbiota and colonization by F. nucleatum are now considered major drivers of malignant tumorigenesis in the distal colon. Several studies confirm the oral origin of F. nucleatum and its potential haematogenous spread into the intestinal microenvironment. Eradication of F. nucleatum from the colon is regarded as a crucial factor in achieving successful treatment outcomes for colorectal cancer (CRC). However, systemic administration of broad spectrum antibiotics adversely affects the composition of the normal gut microbiome, leading to microbial imbalance. For this reason, the elimination of F. nucleatum in the colon and rectum relies on a whole range of antibacterial agents that minimally disrupt the gut microbiota. Our eradication strategy for F. nucleatum emphasizes close cooperation between dentists or periodontologists and gastroenterologists or oncologists, targeting high-risk populations: patients with IBD, colorectal adenomas ≥1 cm, multiple polyps, or first-degree relatives with CRC diagnosed before age 60. These at risk patients undergo dental evaluation for periodontitis and gingivitis by collaborating dentists. Identified cases are treated using localized, comprehensive, and early eradication strategies targeting F. nucleatum and other periodontal pathogens within the periodontal pocket microenvironment. The primary objective of early interdisciplinary cooperation is to detect early stages of periodontitis with periodontal pocket depths of up to 4 mm. In such early forms of periodontitis, elimination of infection can be achieved through local approaches including scaling, deep scaling, and curettage, combined with the application of antibacterial solutions, varnishes, antimicrobial impregnated fibers, and, where appropriate, the use of periodontal lasers.