Beta-lactamases producing anaerobic bacteria in dentoalveolar abscesses.

Pus samples of 30 patients with closed dentoalveolar abscesses who had not received antimicrobial therapy for at last two months were screened for the presence of beta-lactamase-producing anaerobic bacteria. From these 30 pus samples, a total of 112 bacterial strains were isolated; 83 of them were strict anaerobes and 29 were aerobes. beta-lactamases activity of the selected anaerobic bacteria was tested after identification of the isolates and was detected in 5 of the total 83 (6%) strict anaerobic isolates, whereas these 5 strains were isolated in 4 of the 30 (13.3%) pus samples. The species with beta-lactamase activity were in the Prevotella intermedia (4 from 14 isolates) and the Fusobacterium nucleatum (1 from 9 isolates) groups. None of the gram-positive and the other gram-negative anaerobic strains were beta-lactamase positive.