Periodontitis is one of the most common diseases in dentistry and results from the accumulation of bacterial biofilm on the tooth surface. Black-pigmented, Gram negative oral anaerobes such as Porphyromonas gingivalis and Prevotella intermedia are thought to be pathogens in adult periodontitis [1, 2]. Odontogenic local infections require surgical treatment and, if required, a probabilistic antibiotherapy is needed that is effective on most recognized oral pathogens [3]. In most cases, antibiotic prescription is empirical and based on the clinical condition of the patient. Reports from different countries show an increasing prevalence of patients with oral antibiotic resistant bacteria. However, in Portugal there is no data concerning antibiotic resistance of oral flora. The main goal of this study was to identify Porphyromonas gingivalis and Prevotella intermedia strains from periodontal pockets of Portuguese adults suffering of periodontitis infections. Moreover, the isolated strains were also tested for the presence of antibiotic resistance genes. Schlagwörter: periodontic infections, antibiotic resistance genes