The microbiology of periapical granulomas.

Of the 16 periapical granulomas studied, 14 (88%) yielded a positive growth when homogenized and cultured. The concentration of colony-forming units per milliliter of the suspension ranged from 10(1.3) to 10(4.0) (mean 10(2.2)). A total of 47 isolates comprising 26 (55%) facultative anaerobes and 21 (45%) strict anaerobes were obtained. The organisms most commonly cultured were Veillonella species (15%), Streptococcus milleri (11%), Streptococcus sanguis (11%), Actinomyces naeslundii (11%), Propionibacterium acnes (11%), and Bacteroides species (10%). Most of the organisms (96%) were sensitive to either amoxicillin, clindamycin, or tetracycline, whereas only 45% were sensitive to metronidazole.