IntroductionPorphyromonas gulaehave the enzyme PPAD, asP. gingivalis, which is responsible for citrullination related to the pathophysiology of rheumatoid arthritis and periodontitis; this implies the presence of two species of PPAD-producing bacteria in the mouth as well as the presence of citrullinated proteins. There are no previous reports or studies investigating an association betweenP. gulaePPAD in rheumatoid arthritis (RA).ObjectiveTo assess the presence ofP. gulaeand anti-citrullinated peptide antibodies ofP. gulaePAD in patients with RA and their possible relationship with clinical activity markers.Subjects and methodsA total of 95 patients with RA and 95 controls were included. Erythrocyte sedimentation rate (ESR), C-reactive protein, anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF) were measured. Activity index-28 (DAS28) and SCDAI. The periodontal diagnosis was established. Presence ofP. gulaeandP. gingivalis. An ELISA was used to determine antibodies against citrullinated peptides ofP. gulaePAD.ResultsAP. gulaefrequency of 15.8% was observed in the RA group and 9.5% in the control group. Higher levels of ACPA were found in theP. gulae-positive patients of the RA group, finding no significant difference, but if in patients positive forP. gingivaliswith statistical significance (p= 0.0001). The frequency of anti-VDK-cit and anti-LPQ-cit9 antibodies to PPAD ofP. gulaewas higher in the RA group than in the control group without significant difference. No relationship was found with the clinical variables despite the presence ofP. gulaeand anti-citrullinated peptide antibodies ofP. gulaePPAD in patients with RAConclusionsIt was not possible to establish a connection with clinical variables in RA andP. gulae; as a result, the presence ofP. gingivaliscontinues to contribute significantly to the increase in antibodies against citrullinated proteins/peptides from exogenous sources of citrullination in RA and periodontitis.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00784-023-04964-w.