ABSTRACT Background: a significant increase in the resistance of some antimicrobial periodontopathogens traditionally used as adjuncts in periodontal therapy has been reported. Objective: to assess the susceptibility of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis to moxifloxacin and amoxicillin clavulanic acid in patients with chronic periodontitis. Methods: an observational cross-sectional study of the universe composed of 30 patients with chronic periodontitis was conducted. Microbiological samples processing were performed following protocols described previously. Disk diffusion tests were used to assess the susceptibility of A. actinomycetemcomitans and P. gingivalis against moxifloxacin and amoxicillin clavulanic acid. Results: P. gingivalis was the most prevalent microorganism in the population studied. The two periodontopathogens grown were highly sensitive ...