Aggregatibacter aphrophilus: A species of Gram-negative, facultatively anaerobic spherical or rod-shaped bacteria indigenous to oral cavity and pharynx. It is associated with BACTERIAL ENDOCARDITIS; and MENINGITIS.Pasteurellaceae: A family of coccoid to rod-shaped nonsporeforming, gram-negative, nonmotile, facultatively anaerobic bacteria that includes the genera ACTINOBACILLUS; HAEMOPHILUS; MANNHEIMIA; and PASTEURELLA.Aggregatibacter actinomycetemcomitans: A species of Gram-negative, facultatively anaerobic spherical or rod-shaped bacteria indigenous to dental surfaces. It is associated with PERIODONTITIS; BACTERIAL ENDOCARDITIS; and ACTINOMYCOSIS.Haemophilus: A genus of PASTEURELLACEAE that consists of several species occurring in animals and humans. Its organisms are described as gram-negative, facultatively anaerobic, coccobacillus or rod-shaped, and nonmotile.Actinobacillus: A genus of PASTEURELLACEAE described as gram-negative, nonsporeforming, nonmotile, facultative anaerobes. Most members are found both as pathogens and commensal organisms in the respiratory, alimentary, and genital tracts of animals.Pasteurellaceae Infections: Infections with bacteria of the family PASTEURELLACEAE.Aggressive Periodontitis: Inflammation and loss of PERIODONTIUM that is characterized by rapid attachment loss and bone destruction in the presence of little local factors such as DENTAL PLAQUE and DENTAL CALCULUS. This highly destructive form of periodontitis often occurs in young people and was called early-onset periodontitis, but this disease also appears in old people.Actinobacillus Infections: Infections with bacteria of the genus ACTINOBACILLUS.Aggregatibacter segnis: A species of Gram-negative, facultatively anaerobic pleomorphic rod-shaped often filamentous bacteria in the genus of AGGREGATIBACTER found in the oral cavity. It is associated with DENTAL PLAQUE; and BACTERIAL ENDOCARDITIS.Periodontal Diseases: Pathological processes involving the PERIODONTIUM including the gum (GINGIVA), the alveolar bone (ALVEOLAR PROCESS), the DENTAL CEMENTUM, and the PERIODONTAL LIGAMENT.