Analysis of Fusobacterium nucleatum, Streptococcus gallolyticus and Porphyromonas gingivalis in saliva in colorectal cancer patients and healthy controls.

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e15617 Background: The aim of this study was to examine the prevalence and amount of Fusobacterium nucleatum (Fn), Porphyromonas gingivalis (Pg) and Streptococcus gallolyticus subspecies gallolyticus (Sg) in saliva samples of colorectal cancer (CRC) patients and healthy controls. Methods: Patients with newly diagnosed CRC who have not yet received any treatment were included in the study. Control group consisted of individuals over 50 years of age without a prior diagnosis of malignancy. PCR analyzes were performed for identification and quantification of Fn, Sg and Pg strains. Results: Seventy one patients and 77 controls were included in the study. The total amount of bacteria (7,51±0,50 vs 7,45±0,62 log10 copies/ml, p = 0,549) and prevalence of Fn (97% vs 96%), Sg (31% vs 27%) and Pg (76% vs 75%) were similar in patient and control groups, respectively. Saliva samples of the patients had higher amount of Fn (6,89±1,07 vs. 6,35±0,78 log10 copies/ml in controls, p = 0.001) and Sg (4,12±0,99 vs. 3,15±0,58 log10 copies/ml in controls, p < 0.001) compared with the control group. The salivary Pg quantities were similar in the two groups (4,28±1,72 vs 4,22±1,24 log10 copies / ml, p = 0,837). The prevalence and amount of Fn, Sg, and Pg did not differ significantly according to tumor localization (right vs left colon) and stage (stage 1-2-3 vs stage 4). Amount of Fn and Sg were lower in the microsatellite insability (MSI) (+) group than in the MSI (-) group (6,15 vs. 7,03 log10 copies/ml, p = 0,036 for Fn; 3,44 vs. 4,13 log10 copies/ml, p = 0,022 for Sg, respectively). Evaluation of the salivary Sg amount by ROC curve analysis found to have diagnostic value for CRC (AUC: 0,84, %95 GA 0,72-0,96, p < 0,001). Quantity of Sg above 3,32 log10 copy/ml was the best predictor cutoff value for CRC with 82% sensitivity and 76% specificity. Conclusions: In this study, we have found higher amounts of Fn and Sg in the salivary samples of CRC patients compared with healthy controls. The quantity of salivary Sg could be dichotomized at a certain level with high diagnostic sensitivity and specificity. These findings might have implications for etiopathogenesis, screening, diagnosis and prevention of CRC.