Bacteriology of odontogenic apical periodontitis and effect of penicillin treatment

The microbiology and treatment of apical periodontitis was studied in 62 patients, followed-up for 1 year. The clinical treatment and the radiological technique were standardized. One third of the patients received no systemic antibiotics, one third received phenoxymethylpenicillin for 1 week, and one third for 3 months. On the average, 0-2 facultatively anaerobic and 4-6 anaerobic bacteria were isolated from periapical infections. The genera Bacteroides and Fusobacterium in addition to anaerobic gram-positive cocci were found most frequently. Minimum inhibitory concentrations of benzylpenicillin against 269 strains were tested. 12 strains were resistant at the concentration 2.4 micrograms/ml, including 4 strains of Fusobacterium sp. All patients were free of symptoms 1 month after the admission. Only 1 patient failed to show any progress in radiological healing. No differences between the groups in relation to penicillin therapy were found.