Aggregatibacter bacteria, computer illustration. Aggregatibacter are Gram-negative bacteria. The most commonly found species are . aphrophilus and A. actinomycetemcomitans. A. aphrophilus, previously known as Haemophilus aphrophilus, and Actinobacillus aphrophilus. They are part of the normal flora of the mouth and throat. However, in rare cases they can cause disease, most often endocarditis, an infection of the inner lining of the heart. A. actinomycetemcomitans is associated with periodontal infections, and also endocarditis.